2.79-µm efficient acousto-optic Q switched Er,Cr:YSGG laser with an LiNbO₃ crystal modulator

We fabricate a novel, to the best of our knowledge, acousto-optic Q switch in the 3-micron wavelength range using a longitudinal acoustic mode in a lithium niobate (LiNbO₃) crystal. The device is designed based on properties of the crystallographic structure and material to obtain a high diffraction efficiency close to the theoretical prediction. The effectiveness of the device is verified by application in an Er,Cr:YSGG laser at 2.79 µm. The maximum diffraction efficiency reached 57% at the radio frequency of 40.68 MHz. At the repetition rate of 50 Hz, the maximum pulse energy was 17.6 mJ and the corresponding pulse width was 55.2 ns. The effectiveness of bulk LiNbO₃ as an acousto-optic Q switch is verified for the first time.