Picosecond Measurements of Dember Potentials Associated with Photocarrier Gratings.

The main thrust of this thesis is the use of optical interference effects and the Dember voltage to produce a very high speed photodetector; however, the penultimate chapter details a novel formalism for describing paraxial optical systems used with narrowband signals such as resonators for femtosecond lasers, pulse compressors, and prism beam expanders. The impulse response and quantum efficiency of these Dember effect photodevices are calculated for a wide variety of conditions. The predicted impulse responses are the difference of two exponentials under most conditions; however, the presence of traps adds a third exponential and ballistic effects result in nonexponential behavior. Also discussed are effects caused by the injection of very high levels of carriers, thermal effects and metallurgical junctions. Finally, the appearance of excess noise in heterodyne measurements made with a device of this type is predicted. Experimental results on three generations of devices are reported. Impulse response times measured by sampling oscilloscope and electro-optic sampling methods range from hundreds of nanoseconds down to less than a picosecond. Finally, we present a new formalism to describe beam propagation in paraxial optical systems with dispersive elements, including both spatial and temporal variations in the propagating signal. This new formalism makes use of 4 by 4 "ray-pulse" matrices which take account of dispersive effects up to quadratic phases in both spatial coordinates (as in the usual ABCD matrix approach) and in the temporal domain. We show how to use these matrices to write a space-time integral analogous to a generalized Huygens integral, and derive propagation laws for gaussian ray-pulses which are space and time varying analogs of the conventional results for gaussian beams.