Optoelectraulic devices based on interference induced carrier modulation

摘要

A subpicosecond solid state optical correlator based on interference induced carrier modulation includes a photosensor circuit having a photoconductive element and a pair of opposed electrodes. A voltage difference is created across the electrodes to define an electrical field direction, and the element operates to generate charge carriers in response to optical energy incident on the photoconductive element. First and second optical signals are directed onto the photoconductive element to form an interference pattern thereon when the signals overlap in time and space. This interference pattern produces spatial modulation of the distribution of the carriers into lines or planes, at least some of which are not parallel to the electrical field direction. The resulting photocurrent is monitored to detect a parameter associated with the presence or absence of the interference pattern. The interference pattern defines a characteristic nodal spacing between adjacent ones of the lines, and the carriers include higher mobility carriers and lower mobility carriers. The ambipolar diffusion length is no greater than the characteristic nodal spacing, and an integrated value of the photocurrent is therefore less when the optical signals overlap in optical frequency and time and form the interference pattern than when the optical signals do not overlap in optical frequency and time.