He held a postdoctoral position at the National Research Council in Ottawa, Canada for 2 years. Since 1980 he has been with the Electrical Engineering Department at UCLA, first as a member of the research staff and currently as Full Professor. He teaches both undergraduate and graduate courses in electromagnetics and quantum electronics. He has published over 1M) technical papers. His research interests are in the areas of collective particle accelerators, laser-plasma interactions/nonlinear optics, development of Xray CCD's and ultrahigh power lasers.

We present the results of a proof-of-principle experiment to demonstrate the generation of tunable radiation from a laser-ionized gas-filled capacitor array. This scheme directly converts a static electric field of wave number k 0 into coherent radiation pulses of frequency v 2 p ͞2k 0 c, where v p is the plasma frequency. The radiation frequency can be tuned by varying gas pressure and /or capacitor spacing. In this experiment, well-polarized, short (less than 5 ns) microwave pulses have been generated over a frequency range of 6 to 21 GHz. The frequency of the detected signal, as measured with cutoff waveguides, scales linearly with the plasma density, and the relative power of the signal scales quadratically with the dc bias voltage in agreement with the theory. [S0031-9007(96)01789-9]

Single-color illumination of a copper surface by a red or an ultraviolet femtosecond laser pulse yields a threephoton (red) or a two-photon (UV) photoemission process. A multicolor, multiphoton process is generated when the red and the UV pulses overlap both in space and in time on the photocathode. It is shown that this emission process results from the absorption by an electron of one red and one UV photon. It provides a means to correlate ultrashort laser pulses of different wavelengths.

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