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Watt-class optical parametric amplification driven by a thulium doped fiber laser in the molecular fingerprint region

: Heuermann, T.; Gebhardt, M.; Wang, Z.; Gaida, C.; Maes, F.; Jauregui, C.; Limpert, J.


Dong, L. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Fiber Lasers XVII. Technology and Systems : 3-6 February 2020, San Francisco, California, United States
Bellingham, WA: SPIE, 2020 (Proceedings of SPIE 11260)
ISBN: 978-1-5106-3283-7
ISBN: 978-1-5106-3284-4
Paper 112600I, 6 pp.
Conference "Fiber Lasers - Technology and Systems" <17, 2020, San Francisco/Calif.>
Conference Paper
Fraunhofer IOF ()

Numerous molecules important for environmental and life sciences feature strong absorption bands in the molecular fingerprint region from 3 μm-20 μm. While mature drivers at 1 μm wavelength are the workhorse for the generation of radiation up to 5 μm (utilizing down-conversion in nonlinear crystals) they struggle to directly produce radiation beyond this limit, due to impeding nonlinear absorption in non-oxide crystals. Since only non-oxide crystals provide transmission in the whole molecular fingerprint region, a shift to longer driving wavelengths is necessary for a power scalable direct conversion of radiation into the wavelength region beyond 5 μm. In this contribution, we present a high-power single-stage optical parametric amplifier driven by a state of the art 2 μm wavelength, thulium-doped fiber chirped pulse amplifier. In this experiment, the laser system provided 23 W at 417 kHz repetition rate with 270 fs pulse duration to the parametric amplifier. The seed signal is produced by supercontinuum generation in 3 mm of sapphire and pre-chirped with 3 mm of germanium. Combining this signal with the pump radiation and focusing it into a 2 mm thick GaSe crystal with a pump intensity of 160 GW/cm2 lead to an average idler power of 700 mW with a spectrum spanning from 9 μm-12 μm. To the best of our knowledge, this is the highest average power reported from a parametric amplifier directly driven by a 2 μm ultrafast laser in the wavelength region beyond 5 μm. Employing common multi-stage designs, this approach might in the future enable multi-watt high-power parametric amplification in the long wavelength mid infrared.