Accession Number : ADP006704

Title :   On the Buildup and Decay of Photorefractive Wave Mixing Processes,

Corporate Author : TECHNION - ISRAEL INST OF TECH HAIFA DEPT OF ELECTRICAL ENGINEERING

Personal Author(s) : Horowitz, Moshe ; Fischer, Baruch

Report Date : 22 MAY 1992

Pagination or Media Count : 4

Abstract : Photorefractive media have been used for many novel applications in image processing. One interesting use is the novelty filter which is an all optical processor based on the response of two wave mixing (2-WM) or four wave mixing (4-WM). It is obvious that the temporal dynamics of the wave mixing process-is essential to understand such processes. However, since the overall photorefractive dynamics, including the wave mixing part, is described by complicated nonlinear partial differential equations, it is hard to obtain a general solution. The study has been largely limited to steady state behavior and the response of the photorefractive material only, without taking into account the dynamics of the wave coupling effects. In the first part of our paper we study photorefractive 2WM. We first derive an analytic solution for writing and erasure of a grating in the photorefractive material using the undepleted pump approximation. This solution is based on Cronin-Golomb's theory, except that we apply boundary conditions in the time domain, rather than the frequency domain as he does. We thus obtain a simple analytic solution for the cases of turning on or off the input signal. Unlike the solutions presented in earlier work, we emphasize the dependence of the dynamic solution on the coupling of the waves in the photorefractive material. We compare our analytic solution with experimental measurements of 2WM in BaTiO3. It allows us to estimate the gain coefficient and time constant of the material simply and precisely.

Descriptors :   *IMAGE PROCESSING, *OPTICAL PROCESSING, COEFFICIENTS, CONSTANTS, COUPLINGS, DIFFERENTIAL EQUATIONS, DYNAMICS, EQUATIONS, ESTIMATES, FILTERS, FREQUENCY, FREQUENCY DOMAIN, GAIN, IMAGES, MEASUREMENT, MEDIA, MIXING, PARTIAL DIFFERENTIAL EQUATIONS, RESPONSE, SIGNALS, STEADY STATE, TIME DOMAIN, NONLINEAR DIFFERENTIAL EQUATIONS, REFRACTION, SYMPOSIA.

Subject Categories : Electrooptical and Optoelectronic Devices
      Optics

Distribution Statement : APPROVED FOR PUBLIC RELEASE