UBC Theses and Dissertations
Mode-locking and other nonlinear effects in CdS Phonon Masers Smeaton, Melvin Douglas
The nonlinear theory of acoustic amplification in piezoelectric semiconductors has been applied to the CdS phonon maser, to demonstrate that mode-locking In such a device can be predicted as a consequence of its structure and nonlinear properties of the acousto-electric amplifying mechanism. The first direct evidence of mode-locking in the phonon maser has been provided by applying optical processing techniques to signals obtained from laser diffraction. A new and powerful technique for the analysis of optical signals, involving a combination of spatial and temporal filtering, has been developed. Further application of optical processing has allowed the first direct observation of acoustically induced space charge gratings in CdS. Proper exploitation of the methods outlined should give insight into the underlying physical processes. In addition to the optical experiments, data has been presented that demonstrates the existence of two new photovoltaic effects in CdS. The resulting photovoltages are several orders of magnitude larger than those produced by known photovoltaic effects. As yet, the physical processes involved are not properly understood.
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