Acousto-Optic Crystals are crystals that exhibits photoelastic effects, where mechanical waves stimulate elastic strains in the crystals, acting as periodic phase gratings and alters the refractive indices, leading to changes in the optical properties. The AO crystals are excellent candidates for to be processed into the acouto-optic medium of the Acousto-Optic Modulators (AOM) including AO Q-switch, Acousto-Optic Deflectors (AOD), Acousto-Optic Frequency Shifter (AOFS), and Acousto-Optic Tunable Filters (AOTF), etc.