Theoretical Study Of Electroholographic Switching And Analysis Of Optical Properties In KLTN

The physical basis of electroholographic switching is the voltage-controlled photorefractive effect, namely, the reconstruction of volume holograms stored in photorefractive crystal at the paraelectric phase by means of externally applied electric field, and the switching time of which is nanosecond or sub-nanosecond. Electroholographic switching is the fastest optical switching so far. Potassium lithium tantalite niobate(KLTN) doped is currently considered to be one of the best electro-optic materials for electroholographic switching for its high diffraction efficiency and the faster electro-optic response time. The basic principle of electroholographic switching is studied as well as the recording medium and its optical paremeters of electroholography. The main work as follows has been done in this paper:1. The physical mechanism of electroholographic switching is studied. The effective quadratic electrooptic coefficient of quadratic electro-optical crystal is given.2. The relationship between the space-charge field and the doped concentration, the grating period, the external electric field during the writing stage and the Curie temperature in a potassium lithium tantalite niobate(KLTN) crystal at the paraelectric phase is analyzed. The change of refractive index change(35)n as a function of the dopant ion concentration, the Curie temperature and the externally applied electric field during reconstruction stage is also studied. And the influence of the modulation degree of the interference pattern, the thickness of crystal and the externally applied electric field in the crystal at the reconstruction stage on diffraction efficiency is also discussed.3. A method of measuring the optical parameters of KLTN crystal by digital holographic method is proposed. The refractive index0 n and the transmittance T of the crystal can be measured by digital holography. And the effective electrooptic coefficienteffR of the crystal can be measured by digital holographic interferometry.4. A off-axis digital holographic system is set up, the refractive index0 n and the transmittance T and the effective electrooptic coefficienteffR of the Fe:KLTN crystal are measured. The results are that the refractive index0 n =2.0543, the transmittance T =0.1179, and the electrooptic coefficient 16111092.5-R′(28) m2/V2, 16121048.4-R′-(28) m2/V2. The experiment results show that the method presented in this paper is feasible.