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Mid-infrared optical parametric oscillator pumped by a high-pulse-energy, Q-switched Ho3+:YAG laser

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


Applied optics 60 (2021), Nr.22, S.F21-F26
ISSN: 0003-6935
ISSN: 1539-4522
ISSN: 1559-128X
ISSN: 2155-3165
Fraunhofer IOSB ()

A high-pulse-energy mid-infrared light source is presented, based on a zinc–germanium–phosphide optical parametric oscillator (ZGP OPO) pumped by an actively Q-switched high-pulse-energy Ho3+:YAG laser. TheHo3+:YAG pump laser source is capable of generating a pulse energy of 15 mJ from a single Ho3+:YAG rod at room temperature at a pulse repetition frequency (PRF) of 700 Hz. A maximum power of 20.1 W at a central wavelength of 2090 nm can be obtained in continuous operation, with a slope efficiency of 45.1%. A good beam quality with an M2 better than 1.3 was achieved in Q-switched operation. The presented laser architecture was used as a suitable pump source for a ZGP-based OPO. Operated at a PRF of 2 kHz and pumped with a pulse energy of 8 mJ, a low conversion threshold of 1.5 W and a maximum total output power of 6.3 W could be obtained in a linear ZGP based OPO. At maximum power, the peak power of the generated mid-infrared radiation exceeded 120 kW, while the beam quality was affected by the strong gain lens building inside the nonlinear material as a consequence of the high-energy pump pulses.