The Acousto-Optic Properties of Paraelectric Potassium Tantalate Niobate Crystal

As a multifunctional ferroelectric crystal, potassium tantalate niobate (KTa_1–xNb_xO₃, KTN) possesses various significant properties, exhibiting piezoelectric, electro-optic, and pyroelectric effects. Ferroelectric crystals are currently a key research direction for acousto-optic materials, making the acousto-optic effect of KTN crystals highly relevant. This paper modifies the Mach–Zehnder dual-beam interferometer system. By improving its method for applying stress, the photoelastic coefficients of a KTN crystal are accurately measured (p₃₃ = 0.62, p₁₃ = 0.33). Subsequently, the longitudinal acoustic wave velocity under polarized light is measured, and the acousto-optic figure of merit M₂ is calculated to be 33.51 × 10^–15 m³/kg, which is tens of times higher than that of most common acousto-optic materials, such as quartz. The acousto-optic diffraction effect of the KTN crystal is further verified by fabricating a test device, which demonstrates the excellent application potential of KTN in the acousto-optic field.