Nonlinear Optical Processing

Abstract

It is well known that coherently illuminated optical processing systems are very useful for performing such linear operations as convolution, cross-correlation and Fourier spectral analysis because the Fourier transform of an optical signal exists physically and can, therefore, be measured and modified [1]. With properly synthesized composite grating filters and binary filters, the mathematical operations of addition, subtraction, differentiation, integration and generalized orthogonal transformations can easily be carried out [2-4]. To increase the computing capability and flexibility of optical processors, digital electronic computers are incorporated to form hybrid processors [5-10]. If nonlinear operations can be implemented easily, optical processing will be even more useful. Several schemes are presently available to perform nonlinear processing without employing nonlinear devices. These include the theta modulation technique [11], the half—tone process [12], the holographic approach [13] and the method utilizing active or amplifying elements [14]. This paper discusses, however, only optical processing involving real-time nonlinear devices, with and without feedback [2, 15], together with the current research activities at UCSD on nonlinear processing.