Broadband second-harmonic and sum-frequency generation with a long-wave infrared laser in AgGaGe₅Se₁₂

Using an 8 µm long-wave infrared laser as the fundamental wave, we achieved second-harmonic generation (SHG) and sum-frequency generation simultaneously in AgGaGe₅Se₁₂ and obtained a 4 µm laser output. Among them, SHG was achieved in the 173 nm spectral range of the fundamental wave, which was consistent with theoretical calculations. The average power of the obtained 4 µm laser was 41 mW, corresponding to an optical-to-optical conversion efficiency of 3.2%. The measured temperature acceptance bandwidth (LδT) (FWHM) was 50 K·cm; the angular acceptance bandwidth (Lδθ) (FWHM) was 13.3 mrad·cm; and the average absorption coefficient in the wavelength range of 0.86-11.30 µm was 0.07cm^-1. In addition, the spectral acceptance bandwidth (Lδλ) of fundamental wave in AgGaGe₅Se₁₂ SHG and the spectral gain bandwidth of frequency downconversion in AgGaGe₅Se₁₂ were calculated. In view of the small absorption coefficient, the large temperature acceptance bandwidth, and the large spectral gain bandwidth, we conclude that AgGaGe₅Se₁₂ is a suitable nonlinear crystal for high-power short/mid/long-wave infrared lasers and frequency conversions of nanosecond-femtosecond infrared lasers. These results are conducive to the further development of AgGaGe₅Se₁₂ lasers.