Nd (Neodymium) – YAG (Yttrium Aluminium Garnet) LASER

PrinciplePrinciple CharacteristicsCharacteristics

Doped Insulator laser refers to yttrium aluminium garnet doped with neodymium.

The Nd ion has many energy levels and due to

optical pumping these ions are raised to excited levels. During the transition from the metastable state to E1,

the laser beam of wavelength 1.064μm is

emitted

Type : Doped Insulator Laser

Active Medium : Yttrium Aluminium Garnet

Active Centre : Neodymium

Pumping Method

: Optical Pumping

Pumping Source

: Xenon Flash Pump

Optical Resonator

: Ends of rods silver coatedTwo mirrors partially and totally reflecting

Power Output : 20 kWatts

Nature of Output

: Pulsed

Wavelength Emitted

: 1.064 μm

Nd (Neodymium) – YAG (Yttrium Aluminium Garnet) LASER

Power Supply

Capacitor

Resistor

Laser Rod

Flash Tube

M1– 100% reflector mirror

M2 – partial reflector mirror

E1, E2, E3 – Energy levels of NdE4 – Meta Stable StateE0 – ground State Energy Level

ApplicationsTransmission of signals over large distancesLong haul communication systemEndoscopic applicationsRemaote sensing

Energy Level Diagram of Nd– YAG LASER

Non radiative decay

Laser1.064μm

Non radiative decay

E3

E2

E0

E1

E4

Nd

Carbon Di Oxide LASER PrinciplePrinciple

The transition between the rotational and vibrational energy levels lends to the construction of a molecular gas laser. Nitrogen atoms are

raised to the excited state which in turn deliver energy to the CO2 atoms whose energy levels are close to it. Transition takes place between the

energy levels of CO2 atoms and the laser beam is emitted.

Type : Molecular gas laser

Active Medium : Mixture of CO2, N2, He or H2O vapour

Active Centre : CO2

Pumping Method : Electric Discharge Method

Optical Resonator : Gold mirror or Si mirror coated with Al

Power Output : 10 kW

Nature of Output : Continuous or pulsed

Wavelength Emitted : 9.6 μm or 10.6 μm

Symmetric 100 C - stationaryO - vibrates simultaneously along molecular axis

Bending 010,020

C & O vibrate perpendicular to molecular axis

Asymmetric Stretching

001, 002

C & O atoms vibrate in opposite directions along molecular axis

Applications• Bloodless surgery• Open air

communication

• Military field

Principle• The electron in the

conduction band combines with a hole in the valence band and the recombination produces radiant energy. This photon induces another electron in the CB to combine with a hole in the VB and thereby stimulate the emission of another photon.

Type : Homojunction Semiconductor laser

Active Medium : P – N junction

Active Centre : Recombination of electrons and holes

Pumping Method

: Direct Pumping

Optical Resonator

: Polished junction of diode

Power Output : 1 mW

Nature of Output

: Continuous or pulsed

Wavelength Emitted

: 8400 – 8600 Angstrom Units

HOMOJUNCTION SEMICONDUCTOR LASER (Ga-As Laser)

Applications• Compact & used in fibre optic communications• CD writer• Relieves pain• Laser printers

PrincipleTwo beams (object beam and reference beam) are superimposed on a

holographic plate to form an image called a hologram.

PrincipleA beam of light

(reading beam) having the same wavelength as that of the reference beam used for constructing the hologram, is made to fall over the hologram, which in turn gives rise to a 3-D image in the field of view.