Fiber Laser Preamplifier Ryan Marshall Dr Kristan Corwin

Fiber Laser Preamplifier Ryan Marshall Dr. Kristan Corwin Dr. Brian Washburn Shun Wu KSU REU 2011 Funded by the NSF PHY-0851599

Outline � Introduction ◦ Frequency Combs ◦ Direct Comb Spectroscopy � Amplifier ◦ ◦ Components Maximize Power Minimize Autocorrelation Width Goal: More power per combed tooth

Frequency Combs � Modelocked ◦ Pulsed laser Time domain E(t) Df 2 Df t tr. t = 1/fr � Need to be amplified, filtered for comb based spectroscopy ◦ 10 nw/tooth ◦ My Amp: 10 m. W/tooth 100μW/tooth Frequency domain I(f) 0 fo fr fn = nfr + fo D. J. Jones, et al. Science 288, 635 (2000) f

Direct Comb Spectroscopy of Acetylene � Lock combed tooth to Acetylene absorption line � P 13 is good compromise between properties of Er and C 2 H 2 W. C. Swann and S. L. Gilbert. (NIST), Opt. Soc. Am. B, 17, 1263 (2000).

Modelock fiber laser Self-reference + f 0 stabilization Phasestabilized comb 100 MHz frep, 10 n. W/tooth Pre. Amp Spectral filter Saturated absorption 50 GHz @ C 2 H 2 line Optical Amp F-P cavity 2 GHz frep, 20 m. W/tooth 90% pump 10% probe C 2 H 2 filled HC-PCF Scan aperture VIPA PBS PD or CCD array

Amplified Signal 1560 nm, 0. 19 m. W Bigger, broader Pump 1480 nm, 1 W 1560 nm 100 m. W http: //www. fiberoptics 4 sale. com/wordpress/edfafundamentals-explained-in-details/ ~10% efficient

Pre-Amplifier 110 m. W 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 1532 nm

Autocorrelator Autocorrelation Pulse t t http: //www. swampoptics. com/tutorials_autocorrelation. htm delay

Minimizing Pulse Duration � Maximize Peak Power � Challenges ◦ Dispersion ◦ Nonlinearities � Optimize � Spectral SMF length BW ◦ 60 fs pulse ◦ 88 fs autocorrelation

SHG Autocorrelation

Solitons N =3 Third-Order Soliton = 4. 0 m Soliton Period Agrawal, G. P. Nonlinear Fiber Optics, 3 rd ed. Academic Press 1995

Filtering out 1532. 8 nm � 1533 nm Fiber Bragg Grating � Look for repetition rate (98. 6 MHz) ◦ Pel = -17 d. Bm at 98. 6 MHz ◦ ΔV = 0. 03 V ◦ Vmeasured = 0. 076 V

Summary � Frequency Combs ◦ Amplified and Stabilized ◦ Comb based spectroscopy � Preamplifier ◦ Strategies ◦ Factor of 5 short on power � 20 μW/tooth 100 μW/tooth at 1532. 8 nm ◦ Broaden with HNLF

Extra Slides

Frequency References � Applications ◦ Frequency standards in telecommunications ◦ Targeting �Navigation �Astronomy � Portable ◦ Convenient ◦ Accurate W. C. Swann and S. L. Gilbert. (NIST), Opt. Soc. Am. B, 17, 1263 (2000).

System Set-Up Comb Autocorrelator AMP Optical Spectrum Analyzer

PC = Fiber polarization controller FROG PC 2 Amp GRENOUILLE Autocorrelator PC 1 Fiber to freespace ND filter Isolator Comb Erbium doped fiber amplifier LP 50/50 beamsplitter ½ WP ND filter Flipper mirror Coupling free -space beam back to fiber OSA

Autocorrelation