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Transcript of Pharos Manual[1].pdf
User’s manual
Updated: March 7, 2011
Printed: January 3, 2012
© Light Conversion Ltd.
P/O Box 1485, Saulėtekio al. 10
LT-10223 Vilnius, Lithuania
Email: [email protected]
Web: http://www.lightcon.com
Support: [email protected]
2
1 PREFACE
This manual contains user information for safe installation and operation of PHAROS laser
system.
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Read this manual carefully before operating laser for the first time. Special attention must be
given to material in chapter “LASER SAFETY” that describes safety hazards and precautions
against them.
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Use of controls, adjustments or procedures other than those specified in this manual may
result in exposure to hazardous radiation and/or damage of equipment.
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Thank you for using Light Conversion products.
Support needs
If you have any technical questions or problems please contact our authorized representative
or Light Conversion directly:
Light Conversion Ltd.
Keramiku 2b,
LT-10233 Vilnius, Lithuania
Email: [email protected]
Web: http://www.lightcon.com
3
1.1 Electrical and Environmental Specifications
Electric* 110VAC, 50-60Hz, 20A
220VAC, 50-60Hz, 10A
*Chillers used with PHAROS require appropriate commutation of the mains transformer
located inside the chiller.
* Some models of High Voltage supplies used with PHAROS laser system are designed for
single mains voltage (110VAC or 220VAC).
For Indoor use only
Altitude Up to 2000 m
Operating temperature 15-30°C (air conditioning recommended)
Relative humidity 20-80% (non- condensing)
4
Table of Contents
User’s manual ............................................................................................................................. 1
1 PREFACE ........................................................................................................................... 2
1.1 Electrical and Environmental Specifications ............................................................... 3
2 LASER SAFETY ............................................................................................................... 6
2.1 Optical safety. .............................................................................................................. 6
2.2 Electrical safety ............................................................................................................ 7
3 SYSTEM DESCRIPTION AND SPECIFICATIONS ..................................................... 11
3.1 PHAROS configuration ............................................................................................. 11
3.2 Oscillator .................................................................................................................... 14
3.3 Stretcher/compressor ................................................................................................. 14
3.4 Regenerative amplifier ............................................................................................... 14
3.5 Mechanical design ..................................................................................................... 18
3.5.1 Regenerative amplifier ....................................................................................... 20
3.5.2 Oscillator ............................................................................................................ 25
3.5.3 Stretcher/compressor .......................................................................................... 30
3.5.4 Pockels cell driver and High voltage supply ...................................................... 32
3.6 Specifications ............................................................................................................. 34
4 Operation and maintenance of the system ........................................................................ 35
4.1 Installation ................................................................................................................. 35
4.2 Quick start .................................................................................................................. 40
4.3 Switching-off ............................................................................................................. 41
4.4 Setting parameters ...................................................................................................... 42
4.4.1 Setting pump current regenerative amplifier ...................................................... 42
4.4.2 Setting cavity dumping time ............................................................................... 42
4.4.3 Setting pump current of oscillator ...................................................................... 43
4.4.4 Running RA at low repetition rates .................................................................... 43
4.4.5 “RA level” protection ......................................................................................... 44
4.5 Maintenance ............................................................................................................... 45
5 Control Software .............................................................................................................. 46
5.1 Installing PHAROS application and driver ............................................................... 46
5.2 Architecture of PHAROS application ........................................................................ 47
5.3 PHAROS application control windows ..................................................................... 49
5
5.3.1 “Connection” window ........................................................................................ 49
5.3.2 “Power Supply Controller” window ................................................................... 49
5.3.3 “Environment” window ...................................................................................... 50
5.3.4 “Osc./RA Bar Driver” window ........................................................................... 51
5.3.5 “Oscillator” window ........................................................................................... 51
5.3.6 “RA” window ..................................................................................................... 52
5.4 Protection of laser configuration parameters ............................................................. 53
6 Remote Control Module ................................................................................................... 55
6.1 Oscillator control ....................................................................................................... 55
6.2 RA control .................................................................................................................. 57
6.3 LDD control ............................................................................................................... 58
7 Cables and connections .................................................................................................... 59
7.1 Interlocks and “RA state” indication ......................................................................... 61
8 Timing Electronics Module (TEM) .................................................................................. 63
8.1 Principle of operation ................................................................................................. 66
8.2 Timing of laser control signals .................................................................................. 67
8.3 Pulse Picker operation modes .................................................................................... 69
8.4 External laser control interface .................................................................................. 70
8.5 Controlling TEM parameters ..................................................................................... 75
8.6 TEM failures/ warnings flags .................................................................................... 78
6
2 LASER SAFETY
PHAROS is CLASS IV laser product that poses safety hazards if not used properly. Laser
produces output beams that may cause devastating and permanent eye damage, may have
sufficient energy to ignite materials, and may cause significant skin damage.
2.1 Optical safety.
PHAROS emits infrared femtosecond pulses with average power of several watts. Each of the
pump laser diode modules emits optical power of up to 60 W. Direct viewing of laser output
beam or even specular reflection from polished surfaces can cause instantaneous and
permanent eye damage and/or possible blindness.
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Avoid viewing the beam and specular reflections. Wear protective eyewear at all times when
aligning and operating PHAROS. Make sure that your protective glasses cover all the
wavelengths emitted by laser!
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PHAROS beams are powerful enough to burn skin, clothing or paint. Laser beam can ignite
substances in its path even at some distance. It also can damage light sensitive elements such
as video cameras, photodiodes, etc.
For this reasons, and other, user is advised to follow the precautions below:
- Never look directly into the light source or to scattered laser light from any reflective
surface.
- Wear protective eyewear at all times; choose protective eyewear depending on
wavelength and intensity of the radiation, conditions of use, and visual function
required.
- Maintain experimental set-ups below eye level.
- Set up energy absorbing targets and shields preventing unnecessary reflections or
scattering.
- Maintain a high ambient light level in laser operational area. This keeps the eye’s
pupils constricted, thus reducing the possibility of eye damage.
- Avoid blocking the output beam or its reflection with any part of your body. The
intensity of beam can easily cause skin burns or ignite clothing.
- Extreme caution must be exercised when using volatile solvents in the vicinity of laser.
7
- Limit laser access only to qualified users who are familiar with laser safety practices
and aware of dangers involved.
- Use the laser in a closed room. Laser light remains collimated over long distances and
therefore presents potential hazard if not confined.
- Post warning signs near the laser operation area.
2.2 Electrical safety Hazardous voltages are present in the PHAROS laser head and power supply units.
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- Never remove the access covers of power supply and laser electro-optical units unless
power supply is switched off and disconnected from the mains. Voltages present on
these components present safety hazard, which could result in personal injury or death.
- Do not connect or disconnect any cables with power supply turned on.
- Any grounding interruption outside or within PHAROS system will pose an electrical
shock hazard and could make the apparatus inoperative.
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Description of all PHAROS labels is presented in a table and figures below.
Table 2-1 Description of PHAROS labels
No. Label Description
1.
Manufacturer identification label is
located on the end panel of the laser.
2.
Product identification label is located
on the end panel of the laser.
8
3.
Warning logotype is located on the end
panel of the laser. Depending on the
device model actual radiation pulse
energy and duration are recorded on
label.
4.
Aperture label is located above the
system aperture on a front panel of the
laser. Depending on the device model
actual radiation pulse energy and
duration are recorded on label.
5.
Aperture label is located below the
system aperture on a front panel of the
laser.
6.
Product certification label is located on
the end panel of the laser.
7.
Ground contact label is located on the
end panel of the laser.
8.
Warning label is located on the top
cover of the power supply.
9.
Product identification label is located
on the end panel of the power supply.
9
Fig. 2-2 Location of labels on the end panel of PHAROS laser head. Label description is
given in Table 2-1
Fig. 2-1 Location of labels on front panel of PHAROS laser head. Label description is
given in Table 2-1.
6
1
2 7
3
4
5
10
Fig. 2-3 Location of labels on the end panel of PHAROS power supply. Label description
is given in Table 2-1.
8
9
11
3 SYSTEM DESCRIPTION AND SPECIFICATIONS
3.1 PHAROS configuration PHAROS is a high repetition rate femtosecond laser system based on chirped pulse
amplification (CPA) technique, which uses directly diode-pumped Yb:KGW (ytterbium doped
potassium gadolinium tungstate) as active medium. Description of a typical CPA system can
be found in books covering topics on femtosecond lasers (e.g., W.Koechner, Solid State Laser
Engineering, Springer-Verlag, NY; J.C. Diels and W. Rudolph, Ultrashort laser pulse
phenomena, Academic Press, NY; or on the internet http://www.rp-
photonics.com/chirped_pulse_amplification.html). The PHAROS laser head comprises of Kerr
lens mode-locked Oscillator (OSC), Regenerative Amplifier (RA) and Stretcher-Compressor
(S-C) units (see Fig. 3-1). The full system also incorporates an optional Remote Control
Module (Fig. 3-1 (b)), power supply for laser diodes (Fig. 3-2) and appropriate water chiller
that removes excess heat from the operating system, as well as stabilizes laser body
temperature.
PHAROS operation is automatically controlled by driving electronics and operating
parameters can be adjusted from Remote Control Module or external PC that is linked via
USB interface. Dedicated PC software and well developed library of commands are also
included.
As an option, PHAROS system can also include an electo-optical Pulse Picker for output pulse
control and contrast enhancement and/or motorised delay line for automated Compresor
lenght ajustment.
12
(a)
(b)
Fig. 3-1 PHAROS laser head: (a) OEM version, (b) with external enclosure.
13
Fig. 3-2 PHAROS power supply unit.
14
3.2 Oscillator The oscillator (OSC) employs a cavity with chirped mirrors and a prism pair that is used for
fine adjustment of group velocity dispersion. Yb:KGW crystal is end pumped by high
brightness laser diode module. Generation of femtosecond pulses is ensured by Kerr lens
modelocking, which is induced by perturbing the cavity length. Once started, the modelocking
usually sustains throughout the days and is immune to minor mechanical impact. Repetition
rate of oscillator pulses is 76 MHz, while typical output power is in the range of 600-
1200 mW. Spectral bandwidth is within 16-20 nm (FWHM) and yields corresponding pulse
duration of ~70-90 fs. The OSC output power can be actively stabilized by power lock
function. An electronic feed-back loop ensures compensation of the output power drift by
changing the pump diode current.
3.3 Stretcher/compressor Stretcher and compressor of the PHAROS system employ transmission diffraction grating and
both are enclosed in the same housing. By changing the compressor length it is possible to
tune the output pulse duration from a minimal value, which is laser model dependent, to a
maximum one of about 10 ps (limited by the length of translation stage used in compressor).
Compressor length adjustment in the standard PHAROS system is manual; whilst a computer
controlled motorized stage can be installed as an option.
3.4 Regenerative amplifier Regenerative amplifier incorporates a Yb:KGW crystal that is pumped by one or two
continuous wave (CW) pump modules. A single BBO (beta-BaB2O4) Pockels cell within the
amplifier cavity is used to inject the seed and dump the amplified pulse. Any pump light
modulations or fast changes in the repetition rate are not allowed within the CW pumped
regenerative amplifiers. These fast perturbations may cause optical damage of the cavity
components due to uncontrolled increase in pulse energy.
An optional external pulse picker (PP), which is based on the second Pockels cell, can be used
to control every pulse from the RA output. The pulse picker is installed in the same housing of
regenerative amplifier within the beam path to the compressor module. The high voltage (HV)
switches together with HV supplies for both Pockels cells are located outside of the housing as
separate modules. In high repetition rate (500 kHz) PHAROS systems a more powerful HV
15
supply comes as a separate unit (19” standard) in the same rack as power supply of laser diode
bars.
CW pumped regenerative amplifiers have a specific non-saturated form of pulse train in the
RA cavity (Fig. 3-3). The form of the train is determined by CW pump and relatively low gain
of amplifier at repetition rates higher than inverse life-time of upper level of a gain medium
(0.35 ms for Yb:KGW crystal). A steady-state condition for inversion and pulse energy
requires relatively early cavity dumping in order to sustain sufficiently high gain for the
following (next) pulse. CW pumped amplifiers have three typical regimes of operation which
are listed in Table 3-1.
CW pumped regenerative amplifier is a highly non-linear system, which can lead to output
pulse energy bistability at repetition rates from 5 kHz to 40 kHz. The bistabily can be detected
by monitoring the output photodiode signal with an oscilloscope. It manifests as two
alternating in time output pulse energies. This phenomenon can be eliminated by reducing the
cavity dumping time.
16
Regimes of RA operation
Table 3-1
Repetition
rate
Pulse energy Peculiarities of RA operation Warnings
<5 kHz 0.4-1.0 mJ - High gain
- Increased risk of optical
damage due to high pulse
energy
- Possible self-phase
modulation
Do not exceed maximum
pulse energy (too high
pump current, too long
cavity delay time)
5-40 kHz 100-400 J - Moderate gain
- Bistability at long cavity
damping times
Check for bistabilty.
Reduce delay time or
pump current to avoid
bistability.
>40 kHz < 100 J - Low gain
- Low pulse energy
- high output power
Too high output power can
lead to thermal lensing and
degradation of beam
quality.
17
Fig. 3-3 Typical pulse train in the cavity of CW pumped regenerative amplifier.
Note: NO SATURATION of the train is observed!
CAUTION!
DO NOT TRY TO SATURATE THE PULSE TRAIN IN THE RA CAVITY BY INCREASING
CAVITY DELAY TIME. THIS MAY LEAD TO SELF-PHASE MODULATION OF LASER
PULSE AND OPTICAL DAMAGE OF CAVITY COMPONENTS.
CAUTION!
BISTABILITY OF THE OUTPUT PULSE CAN BE OBSERVED ON THE TRAIN OF A PULSE
IN THE CAVITY. IT APPEARS AS TWO TRAINS WITH DIFFERENT AMPLITUDES.
CAUTION!
IN ORDER TO OBSERVE BISTABILTY OF OPTICAL PULSES, TRIGGERING OF AN
OSCILLOSCOPE MUST ENSURE VISUALIZATION OF TWO ADJACENT PULSES.
USE PROPER OSCILLOSCOPE WITH REQUIRED FUNCTION AVAILABLE.
18
3.5 Mechanical design Laser head of PHAROS system has a multi-module structure (Fig. 3-4 ) that includes:
- Oscillator (OSC),
- Regenerative Amplifier (RA),
- Stretcher/Compressor (S-C),
- Timing Electronics Module (TEM),
- High voltage supply for RA Pockels cell,
- High voltage supply for PP Pockels cell (optional),
- RA Pockels cell driver,
- PP Pockels cell driver (optional).
Bodies of oscillator, regenerative amplifier, stretcher/compressor and Pockels cell driver
modules are water cooled, which leads to a good heat management in the system and ensures
mechanical stability that is independent on environmental conditions. The most sensitive
modules are fixed together using three point kinematic mounts, which reduces mechanical
stress caused by thermal expansion and ensures robustness of the system.
19
Fig. 3-4 Mechanical design of PHAROS laser head.
1 - Oscillator
2 - Regenerative Amplifier
3 - Stretcher/Compressor
4 - Timing Electronics Module
5 - High Voltage supply for RA Pockels cell
6 - High Voltage supply for PP Pockels cell (optional)
7 - RA Pockels cell driver
8 - PP Pockels cell driver (optional)
4
3
1
5
6
7
8
2
20
3.5.1 Regenerative amplifier
Monolithic block of regenerative amplifier (RA) body is the main support for other units of
the laser head. It has two sections from two different sides: 1) section of the pump modules is
situated from the side of oscillator and 2) section of the RA cavity is situated from the side of
high voltage supplies. Stretcher/compressor of the system is attached to the front end of the
RA body. Oscillator of the system is attached to the RA by a three point kinematic mount.
3.5.1.1 Fixing to an optical table
PHAROS system is fixed to an optical table using three point kinematic mount with three
cylindrical bearings, which eliminate mechanical deformations caused by difference in
thermal expansion coefficients between optical table (typically made of steel) and aluminium
body of the laser head. Six M6 screws are used to fix laser head to an optical table (see Fig.
3-5). OEM laser heads have three guiding points for parallel keys (6x6x20mm) on the legs
that ensure precise positioning of laser head on to the base plate. This allows maintaining
precise direction of laser beam after removal of the laser head.
CAUTION!
NOTE, THAT IF PARALLEL KEYS ARE USED BETWEEN LEGS AND BASE PLATES,
THERE IS AN INCREASED RISK FOR MECHANICAL SHOCK DURING THE PLACEMENT
OF LASER HEAD. BE CAREFUL WHILE LOCATING THE LASER HEAD IN TO CORRECT
POSITION.
21
Fig. 3-5 Bottom view of PHAROS laser head (OEM vesion). Fixing points are marked with
arrows. Red arrows – M6 screws, brawn arrows – 6x6x20mm parallel keys.
Fig. 3-6 Bottom view of the PHAROS laser head (with external enclosure). Six fixing holes are
marked with red arrows.
22
3.5.1.2 Connections
All the connections to regenerative amplifier are presented in
Fig. 3-7.
Fig. 3-7 Connections to regenerative amplifier:
1 – Pump current of LD bars.
2 – Water from chiller (inlet to laser head), labeled.
3 – Water to chiller (outlet of laser head).
4 – Water from Pockels cell driver.
5 – Water to oscillator.
6 – Water from oscillator.
7 – Water to Stretcher/Compressor.
8 – Dry air/nitrogen to section of pump modules.
9 – Dry air/nitrogen to section of laser cavity.
10 – CAN bus connector under the cover.
2 1
4
7
6
10
5
3 8
9
23
3.5.1.3 Adjustment screws
Micrometer screws for regenerative amplifier mirror adjustment are situated on the rear side
of RA (see Fig. 3-8).
WARNING !
DO NOT ADJUST MIRRORS OF THE REGENERATIVE AMPLIFIER WITHOUT
ADVICE OF AN AUTHORIZED REPRESENTATIVE. THIS MAY CAUSE COMPLETE
MISALIGNMENT OF THE SYSTEM. CONSULT MANUFACTURER OR
AUTHORIZED REPRESENTATIVE BEFORE ADJUSTING ANY MIRRORS.
Fig. 3-8 Micrometer screws for mirror adjustment of regenerative amplifier.
1 – Cavity mirror No.1, horizontal direction.
2 – Cavity mirror No.1, vert dir.
3 – Cavity mirror No.2, vert dir.
4 – Cavity mirror No.2, hor dir.
5 – Output folding mirror, vert dir.
6 – Output folding mirror, hor dir.
7 – Inspection window.
8 – Adjustment of seed direction to RA
8
7
1
3
2
4
5 6
24
3.5.1.4 Photodiodes
Four photodiodes are used to monitor the performance of regenerative amplifier:
1. Internal power meter. Slow photodiode (bandwidth < 1 kHz) is used to monitor the
output power. The photodiode is located in the RA section of pump modules. The
signal of internal power meter is used by a controller of the system. The internal power
meter cannot be calibrated for absolute output power measurements. It is used for
relative measurements and output power stabilization.
2. RA level. Fast photodiode for monitoring pulse amplitude in the RA cavity. Signal of
this photodiode is used by Timing Electronics Module (TEM) to limit the maximum
pulse energy inside RA cavity, and thus protecting optical components from damage.
The photodiode is located between the body of RA and Stretcher/Compressor.
3. RA train. Fast photodiode for monitoring pulse train in the RA cavity. The signal of
this photodiode is delivered through the Timing Electronics Module to the output
panel of TEM. The photodiode is located behind end mirror of the cavity of RA under
the cover on top of RA (Fig. 3-9).
4. Output pulse. The photodiode is located within the housing of stretcher/compressor
module. Signal of the photodiode is delivered through the Timing Electronics Module
to the output panel.
Fig. 3-9 RA train photodiode is located under the cover (marked with black arrow).
25
3.5.2 Oscillator
Oscillator (OSC) module is milled from a single monolithic aluminium block that together
with its water cooled body ensures stable and robust operation. This OSC housing has two
separate sections: 1) cavity section that is from the side of regenerative amplifier (RA) and 2)
pump module section that is on the opposite side. Detector module, which includes
photodiode for OSC power monitoring, is attached to the front side of the oscillator.
3.5.2.1 Fixing
Oscillator is fixed to the RA body by three point kinematic mount (Fig. 3-10Error!
Reference source not found.) which includes two cylindrical bearings. The use of bearings
servers two purposes:
1) Elimination of possible deformations that may arise between RA and oscillator
housings.
2) Making the oscillator conveniently accessible (by lifting it up) for service purposes
without dismounting it from the RA body.
Fig. 3-10 Oscillator fixing points (indicated with red arrows)
CAUTION !
THEN OSCILLATOR IS FIXED ONLY ON TWO UPPER POINTS, THERE IS A RISK FOR
MECHANICAL IMPACT WITH THE THIRD (LOWER) FIXING POINT. THIS MAY CAUSE
MISALIGNMENT OF OSCILLATOR CAVITY.
26
3.5.2.2 Connections
Fig. 3-11 Connections to Oscillator.
1 – Pump current of LD bars.
2 – Water inlet to oscillator.
3 – Water outlet from oscillator.
4 – Dry air/nitrogen to pump section.
5 – Dry air/nitrogen to laser cavity section.
6 – Inspection window.
3
2
1
6
5
4
27
3.5.2.3 Adjustment screws and signal connections on front panel of
oscillator
Adjustment micro-screws of output mirror and end mirror of oscillator are situated on the front
side of oscillator (see
Fig. 3-12).
Fig. 3-12 Front side of oscillator with removed Detector module.
1- Output window of oscillator.
2- End mirror window.
3- Micrometer screw for adjustment of output mirror (horizontal direction).
4- Micrometer screw for adjustment of output mirror (vertical direction).
5- Micrometer screw for adjustment of end mirror (vertical direction).
6- Micrometer screw for adjustment of end mirror (horizontal direction)..
7- CAN bus connection.
8- DC supply for fast photodiodes of Detector Module.
9- Connector of internal power meter.
10- not connected
5
3
1
2
4
6
7
10
11
8
9
28
3.5.2.4 Photodiodes
Four photodiodes are used to measure signals of oscillator, they are listed in Table 3-2. Three
of the diodes are situated in the Detector module which is attached to front side of the
oscillator (Fig. 3-13). The fourth photodiode “Narrow bandwidth” is located in the
stretcher/compressor housing and monitors the spectral bandwidth of oscillator.
Signal of one fast photodiode is used to monitor pulse train in the cavity of oscillator. signal
of this photodiode is coupled directly into an output panel of the Timing Electronics Module
(PD OSC).
Signal of the second fast photodiode is used for triggering of Timing Electronics Module as a
clock for whole system. Both fast photodiodes detect leakage of an optical pulse through the end
mirror of the oscillator (arrow No.2 on
Fig. 3-12).
The third slow photodiode monitors output power of the oscillator. signal of this photodiode is
used by an internal controller.
The Narrow Bandwidth photodiode is installed in the stretcher where the spectrum of
oscillator is spread spatially. Signal of this photodiode is used to recognize whether oscillator
is mode-locked. Controller of the system generates a failure message if the signal of “Narrow
bandwidth” photodiode is too low. The signal of this photodiode is used to find optimal pump
current for the oscillator. A presence of CW component in the output of oscillator is detected
using the signal of this photodiode.
Photodiodes of oscillator Table 3-2
Photodiode Location Bandwidth
1. For Pulse Train Detector Module 300 MHz
2. Clock for TEM Detector Module 300MHz
3. Internal power meter Detector Module <1kHz
4. Narrow bandwidth Stretcher/compressor 1MHz
29
Fig. 3-13 Front side of the oscillator with the Detector module. Osc. sync connected to TEM, Osc.
PD connected to external panel.
Osc sync
Osc PD
30
3.5.3 Stretcher/compressor
Stretcher of the PHAROS system is designed to produce a temporal pulse stretching using
positive dispersion diffraction grating setup. Output of the stretcher is seeded into regenerative
amplifier for amplification and subsequent compression. Compressor of the Pharos system is
built into the same housing as the stretcher and shares the same diffraction grating. By
changing the compressor length it is possible to induce negative or positive pulse chirp and
consequently change the output pulse duration. PHAROS with motorized translation stage this
can be done from the PHAROS software, while in PHAROS with manual compressor length
adjustment a micrometer screw is located under the cover 1 (see Fig. 3-14). In order to adjust
the compressor length it is necessary to remove the cover (1 in Fig. 3-14) and turn the
micrometer screw using hex key. Clockwise rotation produces a positive chirp whilst
counterclockwise yields a negative one.
CAUTION!
ADJUSTMENT OF COMPRESSOR’S THIRD ORDER DISPERSION (OPENING 3,
FIG. 3-15) REQUIRES SPECIAL SKILLS. CONTACT MANUFACTURER OR YOUR
AUTHORIZED REPRESENTATIVE FOR INSTRUCTIONS.
31
Fig. 3-14 Stretcher/compressor of PHAROS system. Rear view.
1- Opening for manual adjustment of the length of the compressor (adjustment of pulse
duration, Second Order Dispersion). Remove the cover for adjustment.
2- Water connection for temperature stabilization.
3- Signal connections:
NB – Narrow Bandwidth. Monitors bandwidth of the oscillator spectrum .
LVL – RA level. Monitors pulse energy in the cavity of RA.
PD – Output Photodiode. Monitors output pulse energy.
Fig. 3-15 Stretcher/compressor of PHAROS system. Front view.
1- Output window.
2- Micrometer screw of folding output mirror.
3- Opening for adjustment of Third Order Dispersion (TOD).
4- Shutter of the seed light. O - opened, C – closed.
1
2
3
1 2 3
4
32
3.5.4 Pockels cell driver and High voltage supply
For removal of HV supply or Pockels cell drivers from the RA do following:
1. Release 4 screws from the top of HV supply modules (see 1 in Error! Not a valid
ookmark self-reference.).
2. Pull and rotate by 90deg a plastic chuck (see 2 in Error! Not a valid bookmark
elf-reference.).
3. Detach driver and HV supply.
4. Disconnect water tubes and cable connections.
Back side of the Pockels cell drivers and HV supplies with all the connections are shown in
Fig. 3-17.
CAUTION!
THERE ARE SPECIAL SHIELDING METAL RINGS BETWEEN THE DRIVER AND RA.
DO NOT FORGET TO PUT THEM DURING ASSEMBLING.
WARNING!
DO NOT TRANSPOSE TIMING CABLES NEITHER ON POCKELS CELL DRIVER SIDE
NOR TIMING ELECTRONICS MODULE SIDE. THE TRANSPOSE OF TIMING CABLES
CAN LEAD TO UNCONTROLLED AMPLIFICATION OF AN OPTICAL PULSE IN THE
CAVITY OF RA AND AS A CONSEQUENCE IRREVERSIBLE OPTICAL DAMAGE OF
OPTICAL COMPONENTS OF THE LASER CAVITY.
WARNING!
DO NOT START THE LASER IF TIMING CABLES ARE NOT CONNECTED. THIS CAN
LEAD TO IRREVERSIBLE OPTICAL DAMAGE OF OPTICAL COMPONENTS OF THE
LASER CAVITY.
WARNING!
DO NOT START THE LASER IF POCKELS CELL DRIVERS ARE GROUNDED. THIS CAN
LEAD TO IRREVERSIBLE OPTICAL DAMAGE OF OPTICAL COMPONENTS OF THE
LASER CAVITY.
33
Fig. 3-16. Removal of Pockels cell drivers and High voltage supplies.
Fig. 3-17 Connection of Pockels cell drivers and HV supplies to RA. View from the side of RA.
1- HV connectors to Pockels cells.
2- Timing connectors ON/OFF.
3- Water connection.
4- CAN bus to HV supply.
2 2 1
4
3
2 1
34
3.6 Specifications Due to continuous product improvement program, specifications may change without notice.
Parameter PHAROS-4W PHAROS-6W PHAROS-SP
Central wavelength, nm 1030±3 1030±3 1030±3
Average output power, W 4 61
5
Repetition rate, kHz 1-2002 1-200
2 1-200
2
Typical pulse duration*, fs 280 280 180
Maximum pulse energy, mJ 0.2 0.2 1.0
Stability of pulse energy, STD <0.5% <0.5% <0.5%
Oscillator pulse duration, fs <90 <90 <90
Oscillator output power, W >0.63 >0.6
3 >0.6
3
Oscillator repetition rate, MHz 764
764
764
Weight of OEM laser head 34kg
Weight of laser head with
external enclosure
42kg
Weight of power supply 13kg
Weight of chiller (approx.) 32kg or 40kg
* defined at FWHM and slightly varies with repetition rate
1 Extendable up to 10 W
2 Versions with higher repetition rates (up to 1 MHz) are available.
3 High power oscillator (>2 W) can be integrated then partial oscillator output is necessary.
4 Customized repetition rates and/or active stabilization of the cavity length are available on request.
Optional accessories
- Pulse picker for “pulse-on-demand” operation.
- Stepper motor equipped translator for computer controlled adjustment of compressor
length (maximum pulse duration ca. 10 ps).
-
35
4 Operation and maintenance of the system
4.1 Installation
CAUTION!
YOUR PHAROS LASER WAS PACKED WITH GREAT CARE, AND IT’S
CONTAINER WAS INSPECTED PRIOR TO SHIPMENT. IF ANY MAJOR DAMAGE
WAS NOTICED AT THE TIME OF RECEIPT (HOLES IN THE CONTAINER, WATER
LEAK, CRUSHING, ETC.) PLEASE NOTIFY THE CARRIER AND MANUFACTURER.
CAUTION!
IF LASER WAS TRANSPORTED IN COLD WEATHER CONDITIONS, KEEP IT IN
TRANSPORTATION BOXES FOR AT LEAST 6 HOURS AT ROOM TEMPERATURE
IN ORDER TO PREVENT POSSIBLE WATER CONDENSATION ON THE SENSITIVE
COMPONENTS OF THE LASER AFTER AN OPENING. LASER HEAD IS
HERMETICALLY SEALED IN PLASTIC BOX.
CAUTION!
IT IS RECOMMENDED THAT YOU WAIT FOR YOUR LIGHT CONVERSION
REPRESENTATIVE TO UNPACK YOUR SYSTEM. IN NO EVENT SHOULD YOU
ATTEMPT TO INSTALL THE LASER YOURSELF WITHOUT PRIOR AGREEMENT
OF LIGHT CONVERSION LTD. ANY UNAUTHORIZED ACTION WILL VOID YOUR
WARRANTY AND YOU WILL BE CHARGED FOR THE REPAIR OF ANY RESULTED
DAMAGE.
1. Carefully remove laser head, power supply and chiller from the transportation boxes.
Retain these boxes for possible transportation in the future.
2. Remove humidity absorbers from the laser and power supply.
3. Remove a tin shell and metal sheet from the bottom of laser head (for OEM laser
heads only).
4. Place laser head on the optical table and fix it using appropriate screws. Fixing of the
OEM laser head is shown in Fig. 3-5, while fixing of the laser head with external
enclosure is shown in Fig. 3-6. Note that you’ll need to remove the cover of PHAROS
external enclosure, consult Fig. 4-1.
WARNING!
AVOID HARSH MECHANICAL IMPACTS WHEN PLACING LASER HEAD ON THE
OPTICAL TABLE. THIS CAN CAUSE MISALIGNMENT OF THE LASER CAVITY.
36
Fig. 4-1. Cover removal in the case of laser with external enclosure.
Fig. 4-2. Water inlet and outlet of the PHAROS laser head.
1. Bend the fixer
3. Raise up
2. Thrust forward
WATER
OUTLET
WATER
INLET
37
5. Connect laser diode power cable (4 high current cables) from power supply to laser
head.
6. Connect control cables from Power supply to Remote Control Module and from Power
supply to laser head.
7. If you intend to control laser operation from a personal computer, connect computer
and power supply via USB cable and install the PHAROS software.
WARNING!
PHAROS LASER MUST BE GROUNDED BEFORE CONNECTING USB CABLE.
IMPROPER GROUNDING CAN DAMAGE COMPUTER AND/OR PHAROS POWER
SUPPLY.
8. Connect water tubes from chiller to laser head. Water inlet to laser head is marked
with red label (see Fig. 4-2).
CAUTION!
THE DIRECTION OF COOLING WATER FLOW IS IMPORTANT FOR PROPER
SYSTEM OPERATION. CONNECT THE HOSES DILIGENTLY WITH PROPER
FLOW DIRECTION. INCORRECT FLOW MAY CAUSE UNSTABLE OPERATION
AND POSSIBLE DAMAGE.
CAUTION!
CHILLER SHOULD BE LOCATED SO THAT THE WARM AIR EXHAUST AT THE
BACK PANEL WOULD NOT BLOW INTO THE POWER SUPPLY UNIT AND VICE
VERSA.
9. Fill the chiller with distilled water. Note that manufacturer do not recommend using
any special water additives to preventing corrosion and/or growth of algae. Consult the
manufacturer before using any water additive.
CAUTION!
USE ONLY STEAM-DISTILLED WATER. THE USE OF HIGHLY DE-IONIZED
WATER MAY CAUSE CORROSION DAMAGE.
10. Connect the mains cables for chiller and power supply.
11. Check connections of other cables. See Chapter 7 of this Manual.
12. Switch-on the chiller and check for water leakage. Add water if necessary. The
temperature of cooling water must be set to room temperature at the beginning. Then it
must be changed slowly (1degC in 5min.) to operating temperature 20-23 degC
defined in the Factory test certificate. Water flow from chiller should not exceed
38
3 l/min and water pressure should be <3 bars. It is advised to use the same values as in
the Factory test certificate. Read chiller manual for adjustment of flow and pressure.
CAUTION!
FAST CHANGE OF LASER HEAD TEMPERATURE MAY CAUSE MISALIGNMENT
OF THE SYSTEM.
13. Turn key to position “Laser ON” to start pump laser diodes. Check for pump currents
of the oscillator and amplifier in Factory test certificate. Change the pump currents if
necessary.
14. Warm-up the laser for 5-10min. Output power of oscillator in CW regime must reach
value stated in Factory test certificate (100-400mW).
Starting oscillator
1. Connect an oscilloscope to “PD OSC” BNC connector for observation of pulse train in
the oscillator.
2. Press “Oscillator” “Start” button on Remote Control Module (RCM) or appropriate
button on the Pharos software. This moves prism inside the cavity of oscillator to
initiate mode-locking. “Running” indication on the “Status” line of RCM must appear
(electronics detects 76MHz frequency in the signal of photodiode). If oscillator doesn’t
start, increase or decrease pump current and try to start oscillator again.
3. To optimize performance of the oscillator use a signal of the “Narrow Spectrum”.
photodiode(RCM: Osc, NB detector; Pharos software: “RA”, “Narrow Spectrum”).
First measure interval of pump currents at which signal of “Seed control” photodiode
changes from its maximum value (A1, point there CW component in optical spectrum
appears) to its minimum value (A2, laser jumps from mode-locking to CW regime). Set
the pump current such that signal of “Narrow Bandwidth” photodiode acquires its
average value ((A1-A2)/2).
4. For long term stability this value of the output power can be locked using “Power lock
function” which activates feedback loop between an internal power meter reading and
pump diode current.
39
Starting regenerative amplifier
Before starting RA check the following:
a) RA delay doesn’t exceed the value defined in the Factory test certificate.
b) RA repetition rate is high enough (>75kHz). Risk of optical damage of optical
components is reduced at high repetition rates and short RA delays.
c) Pump current of RA doesn’t exceed the value defined in the Factory test
certificate.
1) Connect a cable from oscilloscope (>300MHz bandwidth or 2Giga-samples/sec, time-base
100-200ns/div, 50Ω input impedance) to “Scope” BNC connector on Timing Electronics
Module for triggering of an oscilloscope. Use connection “RA” for monitoring pulse train in
the cavity.
2) Install optical power meter on the output of laser.
3) Start the amplifier by pressing “Start” and “PP closed” buttons.
The following parameters of the system must be checked after an installation:
- Mode-locked range of oscillator.
- Mode-lock staring range of oscillator.
- Output power of the system (pump current, cavity delay time and repetition rate should
be the same as indicated in Factory test certificate)
- Output power of the system in Q-switched regime with closed seed light (pump
current, cavity delay time and repetition rate should be the same as indicated in
Factory test certificate).
40
4.2 Quick start When laser is installed and properly adjusted starting procedures is described in Table 4-1.
Table 4-1
Action Position Result
1. Switch the key to position
“Laser on”
Power supply Switches on:
- chiller,
- HV supply for Pockels cells,
- pump current of oscillator
- pump current of RA
2. Wait 10min Heats up pump module, sets
proper pump wavelength
3. Press button “Start” in window
of oscillator
Remote Control
Module or software
on computer
Initiates mode-locking in the
oscillator
4. Press button “Lock” in
window of oscillator
Remote Control
Module or software
on computer
Locks the output power of the
oscillator using a signal of
internal power meter.
5. Set the required parameters of
the regenerative amplifier:
- pump current,
- cavity delay time,
- repetition rate
Remote Control
Module or software
on computer
6. Press “Start” in window of RA Remote Control
Module or software
on computer
Starts operation of RA
7 Press “PP closed” in window
of RA
Remote Control
Module or software
on computer
Activates pulse picker and
directs RA output light to the
output aperture of the laser
41
4.3 Switching-off
Switching-off procedures are listed in the Table 4-2
Table 4-2
Action Position Operation
1. Press button “Stop” Remote Control
Module or computer,
RA
Stops the regenerative
amplifier
2. Turn the key on Power supply
to position “Power off”
Power supply Slowly reduces pump currents
for oscillator and amplifier
diodes and switches-off the
system.
CAUTION!
SWITCHING-OFF OF THE LASER TAKES APPROXIMATELY ONE MINUTE, DUE
TO GRADUAL DECREASE OF PUMP CURRENT. THE MAINS ARE SWITCHED OFF
ONLY AFTER THE RA AND OSC CURRENTS WERE REDUCED TO ZERO.
42
4.4 Setting parameters
4.4.1 Setting pump current regenerative amplifier
Use Factory test certificate to determine required pump current of laser diode bars of
regenerative amplifier. The pump current may slightly vary due to the possible misalignments
in the system.
CAUTION!
IT IS ADVISED NOT TO EXCEED 50 A PUMP CURRENT. THIS MAY LEAD TO THE
REDUCTION OF PUMP BAR LIFETIME AND DETERIORATION OF OUTPUT BEAM PROFILE
DUE TO THERMAL LENSING WITHIN LASER CRYSTAL.
4.4.2 Setting cavity dumping time
Use Factory test certificate to determine required cavity dumping time of regenerative
amplifier. Output pulse duration depends on the dumping time due to a different optical path
length in the crystals (laser crystal and Pockels cell) of the cavity. Set optimal compressor
length for different dumping times. Read Chapter 4.4.4 for Running RA at low repetition
rates. See Fig. 3-3 for typical train of optical pulse in a cavity of RA.
CAUTION!
DO NOT TRY TO SATURATE THE TRAIN OF OPTICAL PULSE IN THE CAVITY OF RA
BY INCREASING CAVITY DELAY TIME. THIS MAY LEAD TO SELF MODULATION OF
AN OPTICAL PULSE AND OPTICAL DAMAGE OF OPTICAL COMPONENTS OF THE
CAVITY OF REGENERATIVE AMPLIFIER.
CAUTION!
BISTABILITY OF THE OUTPUT PULSE CAN BE OBSERVED ON THE TRAIN OF A PULSE
IN THE CAVITY. IT APPEARS AS TRAIN WITH CHANGING AMPLITUDE.
CAUTION!
TO OBSERVE BISTABILTY OF THE OPTICAL PULSE, TRIGGERING OF AN
OSCILLOSCOPE MUST ENSURE VISUALIZATION OF TWO ADJACENT PULSES.
USE PROPER OSCILLOSCOPE WITH REQUIRED FUNCTION AVAILABLE.
43
4.4.3 Setting pump current of oscillator
Use Factory test certificate to determine required pump current of oscillator. Due to the
possible misalignment of the oscillator required pump current may be slightly differ from that
one indicated in the Factory test certificate. To optimize performance of the oscillator use a
signal of the “Narrow Spectrum”. photodiode(RCM: Osc, NB detector; Pharos software:
“RA”, “Narrow Spectrum”). First measure interval of pump currents at which signal of “Seed
control” photodiode changes from its maximum value (A1, point there CW component in
optical spectrum appears) to its minimum value (A2, laser jumps from mode-locking to CW
regime). Set the pump current such that signal of “Narrow Bandwidth” photodiode acquires its
average value ((A1-A2)/2).
4.4.4 Running RA at low repetition rates
Risk of damaging of laser crystal by high energy optical pulse increases if laser is operated at
low repetition rates (<20kHz). At the low repetition rates active medium of the laser has
enough time to accumulate too much of energy in the upper level. This leads to increase in
gain and can lead to optical damage of laser crystal. This problem is also inherent for starting
the CW pumped regenerative amplifiers, therefore feature of “Soft Start” is installed in the
hardware of timing electronics. “Soft Start” feature means that at a start moment cavity
dumping time of the RA is reduced to its minimum value (<150ns) and then is increased
gradually to a set value during about 1second.
Starting laser at low repetition rates:
1. Install energy or power meter at the output of PHAROS and an oscilloscope for
monitoring the pulse train in the cavity of RA;
2. Reduce pump current of RA to 25-28A;
3. Set a proper cavity delay time from Pharos test certificate
4. Set a required repetition rate;
5. Start RA;
6. Slowly increase pump current of RA to the level of required output pulse energy. DO
NOT EXCEED MAXIMUM PULSE ENERGY ALLOWED FOR PARTICULAR
SYSTEM (1mJ, 600J or 200J pulse energies are allowed for different Pharos
44
systems). When the proper pump current is found the RA can be stopped and started at
the same pump current;
7. Check for bistability of output pulse. Bistabilty is a nonlinear phenomenon inherent for
CW pumped regenerative amplifiers as highly nonlinear systems. The bistability can
be observed on oscilloscope as appearance of two different pulse energies of adjacent
output pulses. This occurs when the pulse energy is high enough to remove a great part
of inversion accumulated in a laser crystal in a single pass so the pulse energy becomes
influenced by energy of its predecessor. For stable operation of the laser the bistability
must be eliminated by decreasing of cavity delay time in regenerative amplifier. It is
recommended to set the delay time shorter by one round trip from the “bistable” delay
time.
4.4.5 “RA level” protection
PHAROS has two level protection system against high optical pulse energy which can damage
optical components of the cavity. A dedicated photodiode is installed behind one of the
mirrors of the cavity of regenerative amplifier for monitoring pulse amplitude of the optical
pulse in the cavity. Timing Electronics Module continuously measures amplitude of the
optical pulse. Two level protection against high pulse energy is implemented in Pharos
system:
RA level WARRNING – pulse reaches dangerous energy. The system sends
warning message, but doesn’t stop the amplifier.
RA level FAIL - pulse energy is too high. The system sends warning message
and stops the amplifier.
WARNING!
THE “RA LEVEL” PROTECTION SYSTEM IS NOT FAST ENOUGH TO STOP AN
AMPLIFICATION OF A PULSE DURING A SINGLE AMPLIFICATION CYCLE. DO
NOT START REGENERATIVE AMPLIFIER AT HIGH PUMP CURRENT AND LONG
CAVITY DUMPING TIME AT LOW REPETITION RATES (SEE TABLE 3-1 FOR
DETAILS).
45
4.5 Maintenance For every day work it is important to prevent formation of algae in water of cooling system.
Appearance of algae in cooling system can lead to formation of plugs in critical places, this
cause overheating of laser crystal, softening of water tubes and possibly swamping and
damaging of the laser. To prevent formation of algae plugs it is important to change cooling
water once per three month.
The cooling system of the laser must be rinsed with clean water two times during the
replacement of the water. Water filter of the cooling system is situated on a back panel of the
chiller. Remove the filter and wash it carefully. The filter must be changed once per year.
For maintenance of the chiller read manual of the chiller.
CAUTION!
USE ONLY STEAM-DISTILLED WATER. THE USE OF HIGHLY DE-IONIZED
WATER MAY CAUSE CORROSION DAMAGE. MANUFACTURER DOES NOT
RECOMMEND USING ANY SPECIAL ADDITIVES TO WATER FOR PREVENTING
THE CORROSION AND THE GROWTH OF ALGAE. CONSULT MANUFACTURER
BEFORE USING ANY ADDITIVE TO COOLING WATER. DIFFERENT METALS ARE
USED IN THE COOLING SYSTEM AND THE WATER ADDITIVES CAN CAUSE
DAMAGE OF THE COOLING SYSTEM.
Variation of the room temperature should not exceed ±5degC for stable operation of the laser.
Recommended room temperature is 22±2deg. Each Pharos system is aligned and optimized
for defined cooling water temperature, usually 20degC or 23 degC. Operation at different
water temperature can cause a misalignment or poor performance of the system.
CAUTION!
IT IS IMPORTANT TO PREVENT WATER CONDENSATION ON THE COOLED
COMPONENTS OF THE LASER AT HIGH HUMIDITY AND TEMPERATURE IN A
ROOM. USE A PSYCHROMETRIC CHART (e.g.,
http://en.wikipedia.org/wiki/Psychrometrics) TO CALCULATE A DEW
POINT IN YOUR LABORATORY. THE DEW POINT SHOULD NOT BE HIGHER
THAN WATER TEMPERATURE FROM A CHILLER. DO NOT USE LASER IF
THERE IS A RISK OF WATER CONDENSATION. CONSULT MANUFACTURER FOR
OPTIMAL REGIME OF LASER OPERATION AT HIGH HUMIDITY CONDITIONS.
Power supply of Pharos system has air filter on the fan. The air filter must be checked in every
three months and cleaned if necessary.
46
5 Control Software
Full control of PHAROS parameters is accessible from PHAROS computer application. This
application also can be used for PHAROS state monitoring, visualization and logging.
Computer connects to PHAROS power supply over USB bus
CAUTION!
PHAROS LASER MUST BE GROUNDED BEFORE CONNECTING USB CABLE TO
PC. IMPROPER GROUNDING CAN DAMAGE COMPUTER OR PHAROS POWER
SUPPLY.
5.1 Installing PHAROS application and driver
Installation package of PHAROS application is provided on CD together with laser
documentation. The latest version of software can be downloaded from PHAROS support site
http://pharos.lightcon.com (registration required).
PHAROS application is supported on Microsoft Windows XP and Microsoft Windows Vista
32-bits operation systems. The only requirement for a PC is one free USB socket.
To install software to PC insert installation CD into CD drive or run Setup.exe file and follow
installation instructions.
After software is installed, connect PHAROS power supply to the mains (There is no need to
turn power supply off), plug USB cable to computer and PHAROS power supply. Windows
will detect a new hardware. On Windows Vista select: “Locate and install software” “I
don’t have the disc. Show me other options” “Browse my computer for driver software”.
On Windows XP select: “No, not his time” “Install from a list or specific location”
“Include this location in the search”.
Then browse to PHAROS installation directory\Driver (typically C:\Program
Files\PHAROS\Driver) and select kmdf_lc_usb.inf file to install.
If driver is installed successfully start PHAROS application. It will connect to the laser
automatically. If laser was not connected while starting application, button “Connect” must be
pressed in “Connection” window.
47
5.2 Architecture of PHAROS application
PHAROS application is designed as set of modeless windows. Every window contains
controls and indicators grouped by functions or PHAROS system subunits. Windows can be
showed or hidden using menu option View Window name. If PC monitor resolution is low,
user can choose to hide unnecessary windows. All windows can be docked inside main
application window or docked and tabbed inside each other to save display space and design
ergonomic control environment. To dock or tab window move mouse to the caption area,
press left mouse button and move window to required position. Graphical menu with
docking/tabbing options will appear near the mouse cursor.
Fig 5-1. PHAROS application
Additional graph windows can be added if long term monitoring of certain parameters is
required. To add graph windows press button or select menu Graphs Add New
Graph. Dialog with selection of graphs will appear and can be used to select parameters that
must be displayed in graphs.
Fig 5-2. Example of graph window
Parameters and positions of graph windows are saved when PHAROS application shuts down
and are restored on the next start of software. Toolbar on top of graph window provides
buttons for these operations:
48
Access graph properties ,
Auto scale of graph ,
Save data points to ASCII file ,
Save graph as image to file ,
Enable real-time backup graph data to file ,
Clear all collected data ,
Change time scale of graph from 1 minute to 64 hours ,
Standard normalized deviation of data displayed on graph.
“Graph Properties” window allow to customize graph colors and fonts, type and size of for
data points and lines, vertical axis range, to enable/ disable auto scaling and logarithmic
vertical scale.
Fig 5-3. Example of “Graph Properties” window
49
5.3 PHAROS application control windows This chapter briefly describes main functions of PHAROS application control windows. List
of all windows can be displayed expanding menu option View.
5.3.1 “Connection” window
A “Connection” window is used to select PHAROS device (if more than one laser is
connected to the same computer) and connect/disconnect to the laser. If only one laser is
connected to the computer, power supply is connected to the mains and USB cable is plugged
to computer and PHAROS power supply, application will connect to the laser automatically.
Also there is no need to disconnect while shutting down application.
Fig 5-4 "Connection" window
5.3.2 “Power Supply Controller” window
A “Power supply Controller” window can be used to switch on and off power supply, monitor
health of AC line, state of interlock inputs and internal 24V power supply load.
Fig 5-5 "Power Supply Controller" window
Behavior of “Turn power supply ON/OFF” button is equivalent to manual switching of power
key on PHAROS power supply. If power supply was switched on from computer and key
remains in position “Power OFF” to turn off laser move key to position “Power ON” and then
back to “Power OFF”.
50
CAUTION:
PHAROS ELECTRONICS PREVENTS IMMEDIATE LASER SHUTDOWN IF
CURRENT ON LD BARS IS NOT SWITCHED OFF. IN THIS CASE CURRENT ON
LD BARS IS DECREASED TO 0 AND ONLY THEN POWER SUPPLY AND LASER
ARE SWITCHED OFF. SHUTDOWN PROCEDURE CAN TAKE UP TO 1 MINUTE.
Button “Parameters” allows to access power supply parameters responsible for AC line health
monitoring.
5.3.3 “Environment” window
An “Environment” window is used to monitor PHAROS environmental parameters like
temperature of LD bars, humidity inside Oscillator and RA and to control chiller parameters.
(Only Termotek chiller is supported).
Fig 5-6 "Environment" window
To change chiller water temperature set point: enter a new temperature value and press “Set
New Water Temp.” button.
51
5.3.4 “Osc./RA Bar Driver” window
Two separate windows allow controlling LD bars current, monitoring actual current and
voltage values.
Fig 5-7 "Osc Bar Driver" window
To turn LD bar on: Press button “On”. Status label will change color to orange while current
is setting and then to green when current is set.
To turn off LD bar off: Press button “Off”. Status label will change color to grey while
current is decreasing.
To set a new current value: Enter a new current value to edit box and press button “Set” or
use scroll bar. (Arrow keys or mouse scroll button can be used to change current if scroll bar
is selected).
5.3.5 “Oscillator” window
“Oscillator” window displays actual oscillator output power, state of mode locking and
Power-lock. If modes locking is active in oscillator label “Modes locked” is highlighted. Label
“Setting power” indicates state of Power- Locking regime.
To activate oscillator’s starter: press button “Run Starter”. “Starter runs” flag will be
highlighted until starter stops.
To set a new Power- Lock set point value: enter new value in milliwatts and press button
“New Power Target”. Faster way to accept actual output power value as set point is to press
button “Lock Actual Power”.
To activate Power-Lock function: press button “Activate Power Setting”.
52
Fig 5-8 "Oscillator" window
5.3.6 “RA” window
“RA” and “Sync Failures” windows are important while controlling RA. “Failures” window
displays content of Timing Electronics Module failures register. Check boxes on the left side
of window allow masking some failures. RA won’t stop on failure that is masked. Boxes on
the right side displays accumulated failures. Accumulated values can be important while
determining reason of RA malfunction or stop.
Fig 5-9 "RA" and "Sync. Failures" windows
To start RA: press button “Start”.
To open Pulse Picker: press button “Open PP”.
53
To change cavity dumping time: press button “Cavity Dumping Time” and use scroll bar to
change delay value.
To set a new Power- Lock set point value: enter new value in milliwatts and press button
“Set”.
To activate Power-Lock function: press button “Lock”.
5.4 Protection of laser configuration parameters PHAROS system parameters are stored in internal flash memory of different controllers. All
parameters can be scanned and saved to computer disk using menu command Service Save
settings to file.
CAUTION!
IT IS HIGHLY RECOMMENDED TO BACKUP LASER PARAMETERS TO FILE AND
STORE IT IN SAFE PLACE.
Some laser parameters can be changed without disturbing laser functionality. Other
parameters are defined by laser design and modification of these parameters can cause serious
damage to PHAROS system.
To prevent intentional or unintentional modification of critical system parameters, access
levels are defined for every laser parameter. There are three different access levels used in
PHAROS system:
“User Access Level”. This level is turned on by default when PHAROS system is
powered on. It allows changing only basic set of parameters needed for day-to-day
laser operation.
“Technician Access Level”. When enabled this level allows to modify all important
laser parameters, that are not predefined by device design.
“Manufacturer Access Level”. When enabled, all PHAROS system parameters can be
modified without restrictions.
Access level is set for all PHAROS controllers simultaneously by sending special code
sequence on CAN bus. Access level remains unchanged until another correct sequences will
be received or until power off operation. On power on laser always starts with “User Access
Level”. All PHAROS internal controllers ignore parameter change commands if appropriate
access level is not set.
54
User can change access level from remote control module or using PHAROS application on
computer.
To change laser access level from PHAROS application press toolbar button with key or
select Service Access Level menu option. Choose radio button with access level, enter 4-
digit security code and press “Exit” button. If code is right- required access level will be set,
else access level will be reset to “User Access Level”.
Fig 5-10 Setting access level with PHAROS application.
PHAROS application monitors system access level and disables modification of parameters if
appropriate access level is not selected. Actual access level is displayed in main PHAROS
application window caption.
Fig 5-11 PHAROS access level indication
Security code for “Technician Access Level” is 5172.
55
6 Remote Control Module
Remote control module is small attachable unit with touch-sensitive LCD panel and knob. It
provides fast and convenient access to major PHAROS control functions and can be used to
perform all manual day-by-day operations. Module boots up in 10 seconds after laser is turned
on and is capable to execute all main PHAROS control operations.
Fig. 6-1. Remote control module
6.1 Oscillator control Left side of LCD panel displays Oscillator tab after remote control module has started. This
tab is main window for monitoring parameters and control of oscillator. It displays:
- Oscillator output power measured by internal oscillator power meter,
- Target power value used as set –point for Power-Locking function,
- Temperature of oscillator LD bar,
- Amplitude of Narrow Bandwidth Detector in stretcher/compressor,
- States of mode locking, Power-Lock and starter.
56
Fig. 6-2 Oscillator control window
Buttons and knob are used to access oscillator control functions:
To set a new Power-Lock target value- Press button “Target power” and rotate knob
keeping button pressed. Release button when “Target power” box will display required power
value.
To set actual power value as Power-Lock target value- Press and release “Target power”
button without rotating knob. Actual Oscillator output power value will be set as target for
Power-Lock.
To start/stop Power-Lock function- Press “Enable/Disable PowerLock” button.
To activate oscillator starter- Press “Starter” button. “Starter is running” label will be
displayed on the top- right corner of tab until starter will stop.
To changed oscillator’s LD bar current- Press “LDD” button to access LDD control
window.
To changed oscillator’s parameters- Press “Parameters” button to access “Oscillator
parameters” window.
57
6.2 RA control To access RA controls select tab “RA” on the main remote control module window.
Fig. 6-3 RA control window
Buttons and knob are used to access RA control functions:
To start RA- Press button ‘Start RA”.
To open Pulse Picker- Press button “PP Enable”.
To set a new Power-Lock target value- Press button “Target power” and rotate knob
keeping button pressed. Release button when “Target power” box will display required power
value.
To set actual power value as Power-Lock target value- Press and release “Target power”
button without rotating knob. Actual RA output power value will be set as target for Power-
Lock.
To start/stop Power-Lock function- Press “Enable/Disable PowerLock” button.
To change RA LD bar current- Press “LDD” button to access LDD control window.
To changed RA parameters- Press “Parameters” button to access “Oscillator parameters”
window.
To change cavity dumping time- Press “Sync params” button and select “Delay” button on
menu window.
58
6.3 LDD control
Control of Oscillator’s and RA LDD is performed from similar windows accessed by pressing
“LDD” button on Osc and RA tabs.
Fig. 6-4 Oscillator and RA LDD control windows
To start/stop LDD bar current- Press button “LDD ON”/”LDD OFF”.
To change LDD current: press button “Set I” and use knob to increase or decrease
current. Push button “Fine” for fine current adjustments or “Coarse” for fast current changing,
59
7 Cables and connections
PHAROS is packed with all necessary and optional cables that can be used with the system. If
user wants to use “Interlock” or “Emergency Stop” functions, plugs supplied on the rear panel
of power supply can be used to produce customized cables. Check Fig 7-1 for connections
between PHAROS sub units.
Fig 7-1 Rear panel of PS01-3 power supply
1
2
3
4
5
6 7
8 9
10 11
To laser
Remote panel can be connectedto power supply or directly to laser.CAN bus terminator mus be plugged to
power supply if remote panel is connectedto laser.
60
All connections from power supply are made on the rear panel. Table 7-1 contains description
of all sockets and used cables.
Table 7-1 Description of cables used with PS01-3
No. Name Description Cable code Notes
1 Control lines Control cable from power
supply to laser
C02.01
2 Control lines Control cable for Remote
Control Module
C02.05 Required only if Remote
Control Module is used.
Otherwise CAN bus
terminator must be
plugged in instead.
3 LDD outputs High current cable to LD
bars
C03.01
4 COM port Serial data cable from PS01-
3 to computer
C02.02 Required only if
PHAROS is controlled
using RS-232 interface
5 Chiller Serial data cable from PS01-
3 to Termotek chiller
C02.02 Required only for
Termotek chiller control.
6 Interlocks Plug for level 1 and 2
interlocks inputs and laser
status output.
INTERLOCK User must connect own
cable to access interlocks
function.
7 Safety Lock Plug for “Emergency
Shutdown” button
User must connect own
cable to use “Emergency
shutdown” function.
8
USB cable from PS01-3 to
computer
Required only if
PHAROS is control
using computer.
9 AC input PS01-03 power supply AC
input (C20 socket)
C01.01
(European)
C01.02
(USA, Japan)
C01.03 (UK)
10 AC output AC output with C13 socket Common output from
sockets 10 and 11 must
not exceed 10A.
11 AC output AC output with C13 socket Common output from
sockets 10 and 11 must
not exceed 10A
61
7.1 Interlocks and “RA state” indication Interlocks can be connected to DB9 male socket located on rear panel of PHAROS power
supply. Typical interlock application would be connection of breaker activated by opening
doors in laboratory or any protective cover on laser mounting frame. Two levels of interlock
function are implemented in PHAROS power supply.
Fig 7-2"Interlocks" connector
Table 7-2 Description of "Interlocks" pins
Interlock
level
Pins on DB9
connector
Connection
type
Reaction to
disruption
Procedure of
deactivation
Level 1 1,6 Normally
connected
Stops RA Connect pins 1 and
6 back
Level 2 3,7 Normally
connected
Stops RA and LD
drivers
Connect pins 3 and
7 back and switch
power supply off –
on.
Disrupting connection between two pins in interlock socket activates interlock function.
Interlock action is fully controlled by mains controller and can be adapted according to user
requirements. On standard model activated interlock Level 1 stops RA (if running) and Level 2
interlock stops RA and LD drivers. To deactivate Level 1 interlock it is enough to connect pins
1 and 6. To deactivate Level 2 interlock pins 3 and 7 must be connected and power supply
must be switched off and on.
CAUTION!
INTERLOCK PINS ARE GALVANICALY ISOLATED FROM OTHER PHAROS
ELECTRICAL CIRCUITS. CURRENT IN INTERLOCK CIRCUIT NEVER EXCEEDS
1 MA.
62
Fig 7-3 Interlock input circuit
Pins 4, 9, 5 on “Interlocks” socket are connected to the relay and can be used to get “RA
state”.
Table 7-3 "RA state" pin out
State of RA Pair of pins 4 and 9 Pair of pins 5 and 9
RA stopped closed opened
RA started opened closed
Fig 7-4 "RA state" output circuit
Note: Maximum relay settings are 0.5A/ 30V DC and 0.15A/ 125V AC.
63
8 Timing Electronics Module (TEM)
PHAROS RA operation is controlled by Timing Electronics Module. TEM is responsible for
these functions:
Synchronizes RA operation to Oscillator optical pulses,
Controls RA and PP optical gates (Pockels cells),
Protects RA components from optical damaging.
TEM is designed as aluminum box fitted on oscillator side plate.
Fig. 8-1. External view of TEM
Table 8-1 contains description of all TEM inputs and outputs.
64
Table 8-1. Description of TEM inputs and outputs
Name Direction Description Onboard
connector type
OUT PD Input/ Output
50 Ohm coaxial input/output for PHAROS output
photodiode. Signal from photodiode is retransmitted as
output for user control.
MMCX socket
RA LVL Input/ Output
50 Ohm coaxial input/output for RA level photodiode.
This sensor is used to protect RA from too high energy
pulses inside RA. Signal from photodiode is retransmitted
as output for user control.
MMCX socket
OSC
SYNC Input/ Output
50 Ohm coaxial input for oscillator output photodiode.
Signal from this photo diode is used to synchronize RA. MMCX socket
NB Input
50 Ohm coaxial input for photodiode used as RA seed
signal spectrum width monitor. Photodiode detects the
power of the edge of seed pulse spectrum to prevent
narrow spectrum (and as result short pulse) signal
injection into the amplifier.
MMCX socket
OUT1 Output Output to LED used for laser state indication. Tyco Micro-
Match socket
IN1 Input Input for cover switch (safety interlock) Tyco Micro-
Match socket
RA ON Output 50 Ohm 5V coaxial output to RA Pockels Cell driver. MMCX socket
RA OFF Output 50 Ohm 5V coaxial output to RA Pockels Cell driver MMCX socket
PP ON Output 50 Ohm 5V coaxial output to PP Pockels Cell driver MMCX socket
PP OFF Output 50 Ohm 5V coaxial output to PP Pockels Cell driver MMCX socket
CAN Outputs Internal CAN bus connectors for communication with
other PHAROS components. IDC10 socket
CTRL Input
24V power and CAN bus inputs from power supply Tyco AMP
TERMI-BLOCK
header
SCOPE Output
50 Ohm 2.4V coaxial user’s output. This output can be
programmatically configured to monitor different signals.
Output is source terminated and can be used on high
resistance load as 5V output.
MMCX socket
SYNC1 Output
50 Ohm 2.4V coaxial user’s output. This output can be
programmatically configured to monitor different signals.
Output is source terminated and can be used on high
resistance load as 5V output.
MMCX socket
SYNC2 Output
50 Ohm 2.4V coaxial user’s output. This output can be
programmatically configured to monitor different signals.
Output is source terminated and can be used on high
resistance load as 5V output.
MMCX socket
REMOTE Outputs/Inputs PHAROS external control interface connector. IDC14 socket
Outputs from TEM and some additional photodiodes are located on aluminum panel fitted on
the rear side of PHAROS head (see Fig. 8-2 Error! Reference source not found.).
65
Fig. 8-2. PHAROS user outputs panels (standard and OEM versions)
Table 8-2. Description of TEM inputs and outputs
Name Direction Description Onboard
connector
type
PD OUT Output 50 Ohm coaxial output from PHAROS output photodiode. BNC socket
PD RA Output 50 Ohm coaxial output from RA photodiode. This sensor
is used to monitor laser pulses inside RA cavity. BNC socket
PD OSC Output 50 Ohm coaxial output from oscillator output photodiode. BNC socket
SCOPE Output
50 Ohm 2.4V coaxial user’s output. This output can be
programmatically configured to monitor different signals.
Output is source terminated and can be used on high
resistance load as 5V output.
BNC socket
SYNC1 Output
50 Ohm 2.4V coaxial user’s output. This output can be
programmatically configured to monitor different signals.
Output is source terminated and can be used on high
resistance load as 5V output.
BNC socket
SYNC2 Output
50 Ohm 2.4V coaxial user’s output. This output can be
programmatically configured to monitor different signals.
Output is source terminated and can be used on high
resistance load as 5V output.
BNC socket
REMOTE Outputs/Inputs PHAROS external control interface connector. DB15 socket
CTRL Inputs CAN bus and 24V supply inputs from power supply. Tuchel 5 pins
socket
66
8.1 Principle of operation
Fig. 8-3. Structure of TEM
TEM can be controlled over CAN bus (using commands sent from computer or other device
connected to the CAN bus) and from external laser control interface (using electrical signals).
TEM enters “RA Stopped; PP Closed” state after power-up. If oscillator is operational and
signal “OSC SYNC” meets amplitude, duration and period requirements, TEM can start laser.
After receiving “RA Start” command TEM sends RA ON signal enabling amplification of
oscillator’s pulse inside RA. After some period of time RA OFF signal is sent and light pulse
leaves RA. Time between RA ON and RA OFF is increased with every laser shot from some
initial value to the value defined by Cavity Dumping Time. This process is called “Soft start”
and typically takes ~ 5 seconds. During this time laser output energy varies. After “Soft start”
is finished, time interval between RA ON and RA OFF signals becomes equal to Cavity
Dumping Time and laser output power stabilizes. If pulse picker is installed, “PP Open”
commands changes TEM state to “RA Stopped; PP Opened” and two additional signals PP
ON and PP OFF are generated to open and to close pulse picker.
If “RA Stop” command is received, TEM finishes amplification cycle of last laser pulse and
enters “RA Stopped; PP Closed” state. Next start command can be issued only after 3
seconds! “RA Stopped; PP Closed” state is also entered if TEM detects error or failure.
67
Fig. 8-4. TEM state diagram (commands are sent by CAN)
8.2 Timing of laser control signals
Fig. 8-5 shows the timing diagram of TEM generated control signals with reference to optical
pulses of OSC and RA.
Oscillator period OSC): time interval between two laser pulses at the oscillator’s output.
Oscillator‘s train is monitored by OSC SYNC photodiode. This signal is also retransmitted for
user control (see Fig. 8-5). Typical oscillator period is 13-14 ns.
Laser Sync (SYNC): signal used to trigger amplification of oscillator’s pulse inside RA cavity
and emitting it from laser. Sync signal source can be internal or external generator. It takes ~6
OSC periods after Sync is received to synchronize to oscillator. Laser Sync period can have
values from 1000 s (corresponds to 1 kHz repetition rate) to ~1 s (1 MHz repetition rate).
After receiving Laser Sync signal and completion of synchronization to oscillator’s pulses
TEM generates 500 ns duration SCOPE pulse to user’s output.
From this moment additional delay tON is generated before RA ON signal is send to RA
Pockels cell driver (RA ON delay). RA ON delay can be adjusted between 0 and 45ns.
RA OF delay (tOFF)- this parameter is used in “Soft Start” procedure. Difference tOFF- tON is
used as intial Cavity dumping time (tCD) value. In ~5 seconds time Cavity dumping time is
increased from (tOFF- tON ) to tCD.
Cavity dumping time (tCD) is delay between RA ON and RA OFF signals. During this time
laser pulse is amplified inside closed RA cavity. Cavity dumping time can be increased from
145 ns to 500 ns increasing laser pulse energy. This value is reached after “Soft Start”
procedure.
Pulse picker offset (tPP offset) is adjustable delay between RA OFF and PP ON pulses. tPP offset
can be adjusted from -30 to 30 ns.
PP OFF delay to PP ON (tPP OFF) is adjustable delay between PP ON and PP OFF pulses.
HV driver delay (tDR)- is Pockels cell driver reaction delay to control pulses.
Timing parameters of signals are presented in the Table 8-3.
RA StoppedPP Closed
RA StartedPP Closed
RA StartedPP Opened
RA Start command
PP Open command
PP Close command
Error or failure
RA Stop command
68
Fig. 8-5. Laser timing diagram
Table 8-3. TEM timing parameters
min typ max jitter
Oscillator period τOSC 13-14 ns
SYNC period τSYNC 1-5* 1000 1 τOSC μs
SCOPE to Sync delay tS1 6 τOSC 1 τOSC ns
RA on delay tON 0 45 ns
RA off delay tOFF 145 500 0.5 (typical) ns
Cavity Dumping Time tCD 145 500 0.5 (typical) ns
HV driver delay tDR 60 ns
Pulse picker offset tPP offset -30 30 ns
PP OFF delay to PP ON tPP OFF 10 ns
SCOPE, SYNC1 and SYNC2
delay to PHAROS output tOUT
0.5 (peak to peak at
107 pulses)
ns
“Soft Start” time 5 s
Time between RA Stop and Run
commands 3 s
* Depends from laser model
Overall thermal peak to peak stability 500 ps in 5 -75 °C range.
Osc train
Lase Syncr
osc
Default user’s outputs
SCOPE
tS1
Outputs can be reconfigured by user to another signals.
RA ON
SYNC1(= RA ON)
tON
SYNC(
2= RA OFF)
RA OFF
tOFF
RA Pockels Cellvoltage
tDR tDR
RA train
PP ON
PP OFF
tPP OFF
PP Pockels Cellvoltage
tDRtDR
PHAROS output
tPP offset
SYNC
tOUT
69
Fig. 8-6. OSC SYNC photodiode output
8.3 Pulse Picker operation modes
Pulse Picker can operate in two modes: “closed window” and “shifted window”.
When “closed window” mode is selected, PP Pockels cell is always closed in “PP Closed”
state. This mode ensures maximal laser output contrast, but because of changing load on
Pockels cell driver’s high voltage power supply there is some output pulse energy instability
~1 ms after PP is opened.
If “shifted window” mode is selected, PP Pockels cell is opened and closed with every RA
output pulse, but phase of PP operation is shifted to prevent RA pulses to be emitted in “PP
Closed” state. This mode guaranties output pulse stability, but laser output contrast is lower.
Fig. 8-7. PP operation modes
There is one more PP mode called “OPEN mode”. In this mode PP is opened together with
RA start signal. This regime is only used while adjusting RA timing parameters.
See Chapter 8.5 for more details about PP mode selection.
70
8.4 External laser control interface
Three main PHAROS control operations: synchronization of laser pulses, starting/stopping of
RA and opening/closing of Pulse Picker can be performed with electric signals using external
laser control interface. External control interface must be enabled and configured using
computer and PHAROS control application or other user written software. See Chapter 8.5 for
more details about external interface configuration.
Fig. 8-8. TEM states diagram with external RA and PP control enabled
If external RA and/or PP control sources are selected, “RA Start” and/or “PP Open”
commands must be issued to allow laser control from external control interface. Fig. 8-8
presents diagram of TEM states when external RA and PP control sources are selected. “RA
Start” and “PP Open” commands are transmitted over CAN bus from PHAROS control
application or user’s software.
PHAROS external control interface is realized as DB15 connector
with three logical inputs and three outputs. Fig. 8-9 shows electrical
circuit of external control interface inputs and outputs.
Fig. 8-9. Pin out of PHAROS external control interface DB15 connector
RA Disabled
RA Enabled
PP Disabled
RA Start/Stop commands PP Open/Close commands
Error or failure
RA Stop command
PP Enabled
RA Running
RA RunningPP Opened
„RA on“ signal on DB15 connector„PP on“ signal on DB15 connector
PP Close command
1
2
3
4
5
6
7
8
9 SYNC IN
10 RA on/off
11 PP on/off
12 RA STATUS
13 SYNC OUT
14 FAIL
15
71
Fig. 8-10. Electrical schematic of external laser control interface inputs and outputs.
Descriptions and requirements for control inputs and outputs are listed in Table 8-4.
Table 8-4. Pin assignment of the REMOTE connector (DB15)
*laser sync is internal synchronization signal in the laser. It can be produced by internal clock
of the laser or external SYNC IN signal.
Pin No In/ Out Signal Description
1,2,3,4,5
,6,7
- GND
8 - N.C.
9 IN SYNC IN Input of the external clock for the laser synchronization – initiates
sync* of the laser. Input must be stable continuous frequency f=1-
200kHz (or 1 MHz depending on laser configuration). Duration of
the high level must be between 100 ns and 500ns.
10 IN RA on/off Starts (low level) and stops (high level) RA operation.
Stops RA operation starting from the first valid sync* of the laser.
Start – initiates “Soft Start” of RA (RA STATUS output can be used
to monitor when RA is leaving “Soft Start” and starts operating in a
defined regime.
11 IN PP on/off The signal controls the pulse picker (low level – opened, high level -
closed). The status is loaded with valid laser sync* transition.
12 OUT RA STATUS High level indicates that RA is operating in a defined regime (soft
start has finished and there are no fails in the system).
13 OUT SYNC OUT Output of laser sync* signal triggered by the internal laser oscillator
or SYNC IN. In a case of external clock the pulse duration is the
same as input pulse duration. If SYNC IN is < 500ns then SYNC
OUT is extended to ~500 ns. In case of internal clock SYNC OUT is
~500 ns.
14 OUT FAIL Indicates fail of the laser (OSC or RA). When Fail is high RA is
stopped. When fail returns to low RA on/off rising transition will
start RA operation.
15 - N.C.
72
The diagram of remote laser control signals and laser output pulse timing is presented in Fig.
8-11. Fig. 8-12 presents the waveforms for laser remote control signals. The table below
contains the required signals parameters.
Fig. 8-11. Timing of remote control signals and laser output
73
Fig. 8-12. Waveforms for laser remote control
74
Table 8-5. Parameters of signals for laser synchronization from external device
min typ max
Internal synchronization
SYNC OUT high tp 500 ns
PP on/off signal delay tpr1 0 130 ns
PP on/off signal hold tPP 50 70 ns
External synchronization
SYNC IN high tih 100 500 ns
SYNC IN period til+ tih 1-5* 1000 s
SYNC IN to SYNC OUT delay tio 100 ns
SYNC OUT high toh 500 tih if>500 ns
PP on/off signal delay in level control
mode
tPD1 150 ns
PP on/off signal hold starting from
SYNC IN in level control mode
tPP1 560 ns
PP on/off signal delay in edge control
mode
tPD2 50 100 ns
PP on/off signal hold in edge control
mode
tPP2 50 70 ns
*Depends from laser model
Note: Exact timing parameters can vary depending from TEM firmware version.
75
8.5 Controlling TEM parameters
Control of laser parameters can be performed by mean of PHAROS application started on
computer connected to PHAROS laser. TEM is controlled from RA window. This window is
used to start/ stop RA, open/ close PP, change cavity dumping time and access other TEM
parameters.
Fig. 8-13. Main RA and TEM control window
Pressing “TEM Parameters” button opens “TEM v.2 Parameters” window (see Fig. 8-14).
Fig. 8-14. TEM parameters window
76
“Configuration” frame is used to control PHAROS external control interface modes. These
parameters can be accessed in Technician and Manufacturer access levels.
“Enable external RA start source”- if checked, DB15 input “RA on/off” is used to
start/ stop RA. Additionally button “Enable” in RA window is used to allow DB15
operation.
“Enable external Pulse Picker control source”- if checked, DB15 input “PP on/off” is
used to open/ close PP. Additionally button “Enable PP” in RA window is used to
allow DB15 operation.
“Enable external sync source”- if checked, DB15 input “SYNC IN” is used to trigger
RA shots.
“Invert RA and PP control levels”- if checked, DB15 inputs “RA on/off” and “PP
on/off” are inverted: low level starts/enables RA/PP and high level stops/disables
RA/PP.
“Synchronous RA mode”- if checked and external RA sync source is not selected,
oscillator’s output pulses are used as RA sync source. Changing of RA frequency
means changing of oscillator’s output pulses divisor factor in this regime.
Fig. 8-15. Configuring laser sync sources
“PP mode” frame allows selecting between two PP regimes: “closed window” and “shifted”
window. Check chapter “Pulse Picker operation modes” for more details.
“RA frequency control” frame is used to control TEM internal frequency generator/
oscillator’s pulse divider.
“External RA frequency source control” displays actual “SYNC IN” input frequency and
value of “Locked external frequency”. If “SYNC IN” frequency differs from “Locked external
frequency” more than 10% RA is stopped and failure “Frequency out of locked range” is
activated.
“SCOPE SYNC source”, “SYNC1 source”, “SYNC2 source” frames control multiplexer of
user’s outputs (TTL levels).
Internal TEMgenerator
Pulses fromoscillator output
Divider
RA frequency control
Pulses fromDB15 SYNC IN
Laser sync in
Synchronous RA mode flag
Enable external sync source flag
77
Table 8-6. Signal sources for “SCOPE SYNC”, “SYNC1” and “SYNC2” outputs
Signal name Description
Int_Gen Signal from internal RA frequency generator.
OSC_SYNC TTL version of OSC_SYNC input of TEM.
RA_ON Copy of “RA ON” signal used to trigger RA Pockels cell.
RA_OFF Copy of “RA OFF” signal used to trigger RA Pockels cell.
PP_ON Copy of “PP ON” signal used to trigger PP Pockels cell.
PP_OFF Copy of “PP OFF” signal used to trigger PP Pockels cell.
SYNC2 Signal with user controllable delay locked to “RA OFF” signal.
RA_rdy Internal TEM signal.
RA_delay_rdy Internal TEM signal.
SYNC_OUT Copy of “SYNC OUT” output on DB15 connector.
RUNNING “RA STATUS” output on DB15 connector.
RA_Overrun “RA frequency overrun” failure output.
Power_OK “5V supply failure” output.
RA_Fail “RA common failure” output.
OUTPUT_PD_CMP0 Internal TEM signal.
OUTPUT_PD_CMP1 Internal TEM signal.
RA_LEVEL_CMP0 Internal TEM signal.
RA_LEVEL_CMP1 Internal TEM signal.
Narrow_Spectrum_Level_OK “Narrow bandwidth” failure output.
oclk Internal TEM signal.
osclk_b Internal TEM signal.
oclk_c Internal TEM signal.
prd_invalid Internal TEM signal.
prd_valid_gate Internal TEM signal.
Osc_period_short “Osc sync period too short” failure active signal.
Osc_period_long “Osc sync period too long” failure active signal.
oclk_bad Internal TEM signal.
oclk_active Internal TEM signal.
oclk_rdy Internal TEM signal.
DB15_SYNC_IN Copy of “SYNC IN” input on DB15 connector.
DB15_PP_IN Copy of “PP on/off” input on DB15 connector.
DB15_RA_IN Copy of “RA on/off” input on DB15 connector.
RA_OPEN Output active from “RA ON” until “RA OFF” signals.
PP_OPEN Output active from “PP ON” until “PP OFF” signals.
78
“RA adjustments and timing” frame contains one check box and three sliders. These
parameters can be accessed in Technician and Manufacturer access levels. “Pulse Picker
OPEN mode” check box allows enabling additional PP mode. If checked, PP is opened before
RA Pockels cell. This regime is used while adjusting TEM timing parameters. Sliders ”RA On
delay”, “RA Off start” and “PP Offset” change corresponding timing parameters tON, tOFF, tPP
OFF. Check Chapter 8.2 for more details.
“Oscillator Sync adjustments” frame contains two controls to adjust “Osc Sync Level”
parameter and “Osc too short/ too long” failure value. Button “Tune to Osc” locks TEM to
oscillator repetition rate (this operation must be performed if oscillator was readjusted or
changed).
“Narrow bandwidth failure” frame allows to adjust NB photodiode level when “Narrow
bandwidth failure” is activated.
“RA level too high” is used to adjust “RA level too high” failure and warning levels.
Modification of other TEM parameters can be achieved by accessing “TEM v.2 Advanced
Properties” window by mean of pressing button “Advanced”. This button is accessible only in
Manufacturer access level.
Fig. 8-16. “TEM v.2 Advanced Properties”
8.6 TEM failures/ warnings flags
TEM state is displayed as set of 12 different failure/ warnings flags.
RA common failure
General failure indicates that RA was stopped because of some failing behavior. The
reason of failure can be detected by the state of other failure flags.
RA level too high-warning Warning indicates that radiation level inside RA cavity reached defined warning level.
Active warning doesn’t stop laser.
RA level too high-failure Failure indicates that radiation level inside RA cavity reached failure level. If enabled,
this failure stops RA.
79
RA frequency overrun Failure indicates that RA cavity dumping time is too long for actual frequency. If
enabled, this failure stops RA. If disabled- some laser pulses are missed.
Frequency out of locked range Failure indicates that RA Sync signal is routed from external interface (DB15
connector) and its frequency differs from previously locked value more than 10%. If
enabled, this failure stops RA.
Osc sync failure General failure indicates that Osc. Sync signal from oscillator is missing, has too low/
too high amplitude, irregular period or oscillator is in double pulse mode. If enabled,
this failure stops RA.
Narrow bandwidth failure Failure indicates that narrow spectrum detector inside stretcher/compressor reached
critical value. If enabled, this failure stops RA.
Osc sync period too short This warning indicates additional information about Osc. Sync signal amplitude and
frequency. It doesn’t stop laser. “Osc. Sync level” and “Osc. Sync Period too long/ too
short” parameters must be adjusted to clear this warning.
Osc sync period too long
This warning indicates additional information about Osc. Sync signal amplitude and
frequency. It doesn’t stop laser. “Osc. Sync level” and “Osc. Sync Period too long/ too
short” parameters must be adjusted to clear this warning.
5V supply failure Failure indicates that there is problem with TEM electronics power supply circuits.
This failure always stops RA
RA LDD stopped Failure indicates that RA laser diodes driver was stopped before stopping RA. If
enabled, this failure stops RA.
Osc LDD stopped Failure indicates that Oscillator laser diodes driver was stopped before stopping RA. If
enabled, this failure stops RA.