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High-pulse-energy, Q-switched Ho3+:YAG laser for mid-infrared optical parametric oscillator pumping

 
: Griesbeck, Michael; Büker, Hendrik; Eitner, Madeleine; Goth, Katharina; Braesicke, Peter; Eichhorn, Marc; Kieleck, Christelle

:

Schunemann, Peter G. (Hrsg.) ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Nonlinear Frequency Generation and Conversion: Materials and Devices XX : 6-12 March 2021, Online Only, California, United States
Bellingham, WA: SPIE, 2021 (Proceedings of SPIE 11670)
Paper 116700D, 6 pp.
Conference "Nonlinear Frequency Generation and Conversion - Materials and Devices" <20, 2021, Online>
English
Conference Paper
Fraunhofer IOSB ()
mid-infrared; nonlinear crystals; optical parametric oscillator; frequency conversion; ZGP; Q-switch; Ho3+-YAG

Abstract
We report on an actively Q-switched high-pulse-energy Ho3+:YAG laser in-band pumped by a Tm3+-doped fiber laser, both operated at room temperature. The Ho3+:YAG active medium inside a plane-plane cavity is pumped using a commercial Tm3+-doped fiber laser at 1908 nm from one side. In continuous operation a maximum power of 20.1 W with a slope efficiency of 45.1%, central wavelength of 2090 nm and a beam quality factor M2 below 1.5 were achieved. Q-switched operation was achieved using a Brewster-cut acousto-optic modulator (AOM) based on crystalline Quartz. During Q-switching the incident power was kept stable at 47 W to obtain an M2 of 1.3 and a stable thermal lens inside the laser crystal. With the variation of the repetition frequency a lower limit of the quasi-continuous pulsed regime was investigated and measured to be approximately 3 kHz. The maximum pulse energy in Q-switching operation was achieved with a repetition frequency of 700 Hz leading to an energy of 15 mJ at 12.1 ns pulse width, corresponding to a peak power of 1.2 MW. The laser showed no sign for a loss of performance during many hours of testing. Using this laser as a pump source for a double resonant OPO, a maximum mid-infrared output power of 6.3 W could be achieved at a repetition frequency of 2 kHz, accompanied by a low threshold power of 1.6 W and a slope efficiency of 49.2%.

: http://publica.fraunhofer.de/documents/N-636147.html