OPTIMIZED COHERENT OPTICAL RECEIVER TECHNIQUES

Abstract

Abstract : This report covers the third quarter of an applied research program to develop a scannable photosensitive image detector capable of responding to modulation at a microwave rate. The dc focusing tests were completed, and the detector now operates satisfactorily in a stack of permanent magnets rather than the large solenoid previously used. The direct modulation-demodulation experiment is now working very well with a modulation frequency of 10.7 Gc. Operation was demonstrated in both a nonscanning mode and in a scanning mode with a microwave output signal level of -90 dbm. The continued work on the semitransparent photosurface resulted in a photosurface which is not as susceptible to film breakup during the bakeout phase of tube processing as those which were previously reported. This improvement is primarily the result of the use of a very thin film of tungsten deposited under the photoelectric surface. This change in processing was evaluated by means of several photodiodes. Four scannable phototubes are now being assembled using this cathode modification. (Author)