VIBRATION DETECTION USING MOVING GRATING TECHNIQUE IN PHOTOREFRACTIVE2-WAVE MIXING

Optical interferometry using photorefractive two-wave mixing has been proposed for the detection of small amplitude vibration. Sensitivity i n this interferometry depends on spatial phase difference between the interference fringe and the refractive index grating due to the photor efractive effect. It is proposed to realize vibration detection in suc h a way that the moving grating technique is applied to the photorefra ctive two-wave mixing. For this purpose, the optimum speed of movement is discussed. On the basis of the Kogelnik's theory, a theoretical eq uation is derived about the interference beam which is equivalent to a n output signal. Although this is simple approach, our theoretical equ ation is available for practical use in vibration detection using phot orefractive two-wave mixing.