Real-Time Electrooptical Signal Processors with Coherent Detection

Abstract

In conventional real-time electrooptical signal processors, the variation of the output intensity with time is directly detected with a photodetector. As a result of this, any information carried in the phase of the light is lost. However, if the light is detected coherently, i.e., it is heterodyned with another coherent local oscillator light source on the detector surface, the phase associated with the amplitude of the light may be preserved. This paper presents the results of a theoretical and experimental study of the properties of real-time electrooptical spectrum analyzers with coherent detection. Basic equations of operation are presented and discussed, and confirmed by experiment, and it is concluded that the construction of such devices is feasible.

Image edge enhancement with two cascaded acousto-optic cells with contrapropagating sound

“…͑5͒ and Fig. 1 the complex optical field of the undiffracted order after the first AO cell can be approximated as (6) and the undiffracted optical field after the second AO cell can be expressed approximately as…”

“…4 The frequency-shifting property of the diffracted light is used in optical heterodyne applications that lead to the use of AO cells in image correlators. 5,6 AO cells were used by Mait et al 7 in the Fourier plane as a dynamic spatial filter, resulting in morphological erosion and dilation operations. AO cells were also used by Balakshy 8 to broad-cast images into undiffracted and first diffracted orders.…”

Basic image-processing operations by use of acousto-optics

“…AO devices have been used widely as optical signalprocessing components during the past three decades. The use of an AO cell as an image correlator in an optical heterodyning architecture was demonstrated independently by Whitman et al 1 and King et al 2 Two crossed Fourier plane Bragg cells have also been used by Prather and Mait 3 and Mait et al 4 to implement two-dimensional ͑2-D͒ dynamic pointspread functions. AO cells were used in the Fourier plane as a dynamic spatial filter, resulting in morphological erosion and dilation operations.…”

Acousto-optic signal processors for transmission and reception of phased-array antenna signals

“…2 This approach was limited to processing to received antenna signals, and it could not be used to generate drive signals to provide desired antenna beam shape and direction. Subsequent research in optical phased-array antenna processing revolved around the Lambert processor, and most efforts used better hardware to get improved experimental results.…”