Fiber Laser Preamplifier
Ryan Marshall
Dr. Kristan CorwinDr. Brian Washburn
Shun Wu
KSU REU 2011Funded by the NSF PHY-0851599
Introduction◦ Frequency Combs◦ Direct Comb Spectroscopy
Amplifier◦ Components◦ Maximize Power◦ Minimize Autocorrelation Width◦ Goal: More power per combed tooth
Outline
Modelocked laser◦ Pulsed
Need to be amplified, filtered for comb based spectroscopy◦ 10nw/tooth 10mW/tooth◦ My Amp: 100μW/tooth
Frequency Combs
2Df
tr.t = 1/fr
t
E(t)Time domain
Df
D. J. Jones, et al. Science 288, 635 (2000)
Frequency domain
0 fn = nfr + fo
I(f)
f
fo fr
Lock combed tooth to Acetylene absorption line
P13 is good compromise between properties of Er and C2H2
Direct Comb Spectroscopy of Acetylene
W.C. Swann and S.L. Gilbert. (NIST), Opt. Soc. Am. B, 17, 1263 (2000).
Modelock fiber laser Self-reference + f0 stabilization
100MHz frep,10nW/tooth
Spectral filter Optical
AmpF-P cavity
2GHz frep,20mW/tooth
50GHz @ C2H2 line
C2H2 filled HC-PCFVIPA
pump
probeScan aperture
PD or CCD array
90%
10%
PBS
Phase-stabilized comb
Saturated absorption
PreAmp
Signal1560nm, 0.19mW
Pump1480nm, 1W
Amplified Signal
1560 nm100mW
Bigger, broader
http://www.fiberoptics4sale.com/wordpress/edfa-fundamentals-explained-in-details/
~10% efficient
Pre-Amplifier110 mW
2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.785
90
95
100
105
110
115
Pow
er (m
W)
Length of gain fiber (m)
Amplifier Output Power at Different Gain Fiber Lengths
1. Optimize gain fiber length to maximize average power
2. Optimize SMF fiber length to minimize pulse duration
3. Broaden the spectrum to get enough gain at 1532nm
1520 1540 1560 1580 1600 1620
0.0
0.2
0.4
0.6
0.8
1.0 Output Input
Pow
er (N
orm
aliz
ed)
Wavelength (nm)
Amp Input and Output spectra
Autocorrelator
http://www.swampoptics.com/tutorials_autocorrelation.htm
t delay
Pulse
Autocorrelation
t delay
Maximize Peak Power Challenges
◦ Dispersion◦ Nonlinearities
Optimize SMF length
Spectral BW◦ 60fs pulse◦ 88fs autocorrelation
Minimizing Pulse Duration
1520 1540 1560 1580 1600 1620
0.0
0.2
0.4
0.6
0.8
1.0
Pow
er (N
orm
aliz
ed)
Wavelength (nm)
Amplifier Output Spectrum
-500 0 500
0.0
0.5
1.0
In
tens
ity
AC delay (fs)
111 mW autocorrelation, cutting back SMF after EDF1.05m SMF before EDF
red: 1.84m, FWHM: 219fsorange: 1.53m, FWHM: 169fsgreen: 1.23m, FWHM: 192fsblue: 1.17m, FWHM: 189fspink: 1.03m, FWHM: 164fsblack: 0.94m, FWHM: 111fs
AutocorrelationSH
G
SolitonsN =3Third-Order Soliton
= 4.0m Soliton Period
Agrawal, G.P. Nonlinear Fiber Optics, 3rd ed.Academic Press 1995
-500 0 500
0.0
0.5
1.0
Inte
nsity
AC delay (fs)
111 mW autocorrelation, cutting back SMF after EDF1.05m SMF before EDF
red: 1.84m, FWHM: 219fsblack: 0.94m, FWHM: 111fs
1533nm Fiber Bragg Grating Look for repetition rate (98.6 MHz)
◦ Pel = -17dBm at 98.6 MHz◦ ΔV = 0.03 V◦ Vmeasured = 0.076 V
Filtering out 1532.8nm
1531 1532 1533 1534 1535 1536
-50
0
Amplifier Output Spectrum after 1533nm FBG
Pow
er (d
Bm
/nm
)
Wavelength (nm)1520 1540 1560 1580 1600 1620
0.000
0.002
0.004
0.006
0.008
0.010
0.012
0.014
Pow
er (u
W/n
m)
Wavelength (nm)
Amp Output Spectrum
Frequency Combs◦ Amplified and Stabilized◦ Comb based spectroscopy
Preamplifier◦ Strategies◦ Factor of 5 short on power 20 μW/tooth 100 μW/tooth at 1532.8nm
◦ Broaden with HNLF
Summary
Extra Slides
Applications◦ Frequency standards in telecommunications◦ Targeting Navigation Astronomy
Portable◦ Convenient◦ Accurate
Frequency References
W.C. Swann and S.L. Gilbert. (NIST), Opt. Soc. Am. B, 17, 1263 (2000).
1520 1540 1560 1580 1600
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
P
ower
(uW
/nm
)
Wavelength (nm)
blue: 3.51m, 89.0mWgreen: 3.26m, 97.5 mWorange: 3.14m, 103.0mWpink: 3.04m, 111.5mW
Amp output for various lengths of Liekki 110, ~950mW
AMPComb Autocorrelator
Optical Spectrum Analyzer
System Set-Up
FROG
ND filter
PC2 PC1
Amp CombGRENOUILLE
50/50 beamsplitter
Fiber to free-space
OSA
Coupling free-space beam back to fiber
PC = Fiber polarization controller
Erbium doped fiber amplifier
Isolator
LP
Flipper mirror
AutocorrelatorND
filte
r½ WP
-500 0 500
0.0
0.5
1.0
Inte
nsity
AC delay (fs)
111 mW autocorrelation, cutting back SMF after EDF1.05m SMF before EDF
red: 1.84m, FWHM: 219fsorange: 1.53m, FWHM: 169fsgreen: 1.23m, FWHM: 192fsblue: 1.17m, FWHM: 189fspink: 1.03m, FWHM: 164fsblack: 0.94m, FWHM: 111fs
-500 -250 0 250 500
0.0
0.5
1.0
Inte
nsity
AC delay (fs)
60mW autocorrelation, cutting back SMF after EDF1.05m SMF before EDF
red: 1.84morange: 1.53mgreen: 1.23mblue: 1.17mpink: 1.03mblack: 0.94m
Autocorrelation
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