| 摘要 |
A microstrip transmission line on the surface of a photoconductive semiconductor medium has a small gap, thereby producing an open circuit between a microwave (or other electrical signal) source and a detector connected at opposite ends of the line. This gap is suddenly filled (and the microwave circuit thereby completed) by copious electrical charges which are generated in a semiconductor surface region across the gap, in response to a first pulse of optical radiation characterized by a picosecond rise time and by a wavelength which is substantially completely absorbed at the surface of the semiconductor medium. Accordingly, this first pulse produces a correspondingly sharp rise in the microwave energy (switch-"ON") reaching the detector. Within a few picoseconds thereafter (while the electrical charges due to the first pulse still persist), a second optical pulse, which is also characterized by a picosecond rise time but of a wavelength which is absorbed into the bulk of the semiconductor medium, is directed at the gap sufficient to increase significantly the conductance across the gap, thereby short-circuiting the microwave line to a ground plane on the opposed major surface of the semiconductor. Accordingly, the second pulse produces a correspondingly sharp decline (switch-" OFF") in the microwave energy reaching the detector from the microwave source.
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