The conventional chopped laser radiation technique of optoacoustic detection suffers from a sensitivity-limiting synchronous background signal. This thesis reports on theoretical and experimental studies of two novel optoacoustic modulation techniques designed to reduce the background signal and thereby improve the sensitivity. A specialized optoacoustic detector is described, which is capable of being operated in the conventional chopped-laser modulation mode as well as in the new Stark voltage modulation and Stark polarization modulation modes; experimental results are given using all three modes of operation. Stark voltage modulation produces more than two orders of magnitude improvement in sensitivity over conventional modulation under identical conditions. Even greater sensitivities are shown to be attainable. A basic theory of conventional optoacoustic detection is developed and then applied to the new optoacoustic modulation techniques. An introduction to and history of optoacoustic detection are also presented.
