High-response KTN crystal devices at the phase transition temperature for longitudinal and holographic electro-optic modulation

This study proposes a solid-state device that can be updated to high-response spatial light modulators. We demonstrate an electro-optic grating device based on the Kerr effect in potassium tantalate niobate (KTN) crystals that exhibit a relative dielectric constant exceeding 10,000. The time response in spatial light modulation can be enhanced by a quadratic electro-optic material with high permittivity. Its effectiveness may be affected by device specifications such as spatial resolution, temporal stability, and electrode-matching conditions on a specific surface. We conducted simulations using the finite element method to verify their effects, calculating the electric potential while applying voltage to the crystal. The field of light inside the crystal was computed sequentially according to the wave propagation equation and the potential. Fourier analysis of the light modulated in the simulations indicated that the spatial crosstalk in the grating pattern can primarily be attributed to the internal charge gradient. In the experiments, a transparent comb electrode was deposited on both sides of the KTN crystal to generate phase patterns of the grating in response to the voltage. After switching on the voltage using the function generator, the delay in the detection of light diffraction through the device and lens was measured. The frequency dependence of the measured capacitance was determined to be stable up to the cutoff frequency.