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140 W peak power laser system tunable in the LWIR

: Gutty, F.; Grisard, A.; Larat, C.; Papillon, D.; Schwarz, M.; Gerard, B.; Ostendorf, R.; Rattunde, M.; Wagner, J.; Lallier, E.

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Optics Express 25 (2017), No.16, pp.18897-18906
ISSN: 1094-4087
Journal Article, Electronic Publication
Fraunhofer IAF ()

We present a high peak power rapidly tunable laser system in the long-wave infrared comprising an external-cavity quantum cascade laser (EC-QCL) broadly tunable from 8 to 10 µm and an optical parametric amplifier (OPA) based on quasi phase-matching in orientation-patterned gallium arsenide (OP-GaAs) of fixed grating period. The nonlinear crystal is pumped by a pulsed fiber laser system to achieve efficient amplification in the OPA. Quasi phase-matching remains satisfied when the EC-QCL wavelength is swept from 8 to 10 µm with a crystal of fixed grating period through tuning the pump laser source around 2 µm. The OPA demonstrates parametric amplification from 8 µm to 10 µm and achieves output peak powers up to 140 W with spectral linewidths below 3.5 cm−1. The beam profile quality (M2) remains below 3.4 in both horizontal and vertical directions. Compared to the EC-QCL, the linewidth broadening is attributed to a coupling with the OPA.