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Q: Fachverband Quantenoptik und Photonik
Q 35: Laser Development and Applications (Spectroscopy)
Q 35.5: Talk
Wednesday, March 8, 2017, 15:30–15:45, P 5
Low drift cw-seeded high-repetition-rate optical parametric amplifier for fingerprint coherent Raman spectroscopy — •Joachim Krauth1, Tobias Steinle1, Bowen Liu2, Moritz Floess1, Heiko Linnenbank1, Andy Steinmann1, and Harald Giessen1 — 14th Physics Institute and Research Center SCoPE, University of Stuttgart — 2Ultrafast Laser Laboratory, Tianjin University
We introduce a broadly tunable robust source for fingerprint (170 - 1620 cm−1) Raman spectroscopy. A cw thulium-doped fiber laser, gap-free tunable from 1770 - 2030 nm, seeds an OPA, which is pumped by a 7-W, 450-fs Yb:KGW bulk mode-locked oscillator with 41 MHz repetition rate. The OPA is designed in double-pass configuration for power scaling and delivers a signal output power of around 1 W over most of the tuning range. The output radiation of the OPA signal is frequency doubled in a PPLN crystal and generates 0.7 - 1.3-ps-long narrowband pump pulses for the subsequent Raman spectroscopy that are tunable between 885 and 1015 nm with >80 mW average power. The Stokes beam is delivered by a part of the oscillator output, which is sent through an etalon to create pulses with 1.7 ps duration. We demonstrate a stimulated Raman gain measurement of toluene in the fingerprint spectral range. Here we use an acousto-optic modulator to modulate the pump pulse, while the Stokes intensity is detected using a single silicon photodiode, which is connected to a high-frequency lock-in amplifier. Our system combines the simplicity and the robustness of an OPA with the ultra-low intensity noise of a solid-state oscillator. Furthermore, the cw seeding intrinsically ensures low spectral drift.