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