Simultaneous Visualization of a Paraelectric Mn:KNTN Crystal and Measurement of Its Kerr Coefficient by Digital Holographic Interferometry

A method of visualizing a paraelectric Mn:KNTN crystal and measuring its Kerr electrooptic coefficient by digital holographic interferometry is presented. Digital holograms of the crystal with different voltages are recorded; a series of sequential phase maps of the KNTN crystal is numerically reconstructed from the holograms in different states to visualize the refractive index distribution. The spatial distribution of the induced refractive index change can be obtained by subtracting the phase of different voltages, and the effective electrooptic coefficient is calculated by means of the refractive index change. We obtain the Kerr coefficient of the Mn:KNTN crystal with R₁₁ = 11.260 ×10^-16 m²/V² and R₁₂ = -1.351 ×10^-16 m²/V² near its phase-transition temperature, and the research results show that the method presented in this paper is successful and feasible.