The Study Of Eletro-optic And Photorefractive Effect Of Mn:Fe:KTN Crystal

Potassium tantalate niobate（KTN） crystal is a superior photorefractive crystal material due to its excellent electro-optic and photorefractive performance and application versatility in the field of new optical devices, such as beam scanner, varifocal lenses and so on. In this thesis, the effect of electro-optic and photorefractive of Mn:Fe:KTN crystal is by studied by digital holography. The main work which has been carried out presents as follows:1. The electro-optic effect in a paraelectric Mn:Fe:KTN crystal is visualized by digital holographic interferometry. The spatial distribution of the phase changes is explored and discussed at different temperatures. The effective electro-optic coefficient and the effective quadratic polarization-optic coefficient of the Mn:Fe:KTN crystal are measured under different temperatures. The results show that the effect electro-optic coefficient lowers with temperature increasing and the largest effective electro-optic coefficient can be obtained near the Curie point, and the effective quadratic polarization-optic coefficient is a constant under different temperatures and the average value of g₁₁=0.355m⁴/C² and g₁₂=-0.0206m⁴/C².2. The refractive index change of Mn:Fe:KTN crystal illuminated by focused light is visualized and measured by digital holographic interferometry. The photorefractive properties are analyzed under different temperature, different light intensity and different voltage. The results manifest that at the same temperature, the light-induced refractive index change Δn increases with the voltage increasing, and the maximumΔn is independent of the light intensity. The writing time τ_w decreases with rising light intensity and is a constant for the different voltage. For a different temperature, the maximum value ofΔn and the writing time τ_w appear at the Curie temperature.3. The induced refractive index change of Mn:Fe:KTN crystal under periodic beam is also visualized by digital holographic interference. The relationship beτ_ween the refractive index modulation, the diffraction efficiency and voltage is analyzed.