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

Using an 8 µm long-wave infrared laser as the fundamental wave, we achieved second-harmonic generation (SHG) and sum-frequency generation simultaneously in 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 () (FWHM) was 50 K·cm; the angular acceptance bandwidth () (FWHM) was 13.3 mrad·cm; and the average absorption coefficient in the wavelength range of 0.86-11.30 µm was 0.07. In addition, the spectral acceptance bandwidth () of fundamental wave in SHG and the spectral gain bandwidth of frequency downconversion in were calculated. In view of the small absorption coefficient, the large temperature acceptance bandwidth, and the large spectral gain bandwidth, we conclude that 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 lasers.