A photoconductive reflectometer for characterizing semiconductor devices at millimeter wavelength frequencies where a first photoconductive circuit element (PCE) is biased by a direct current voltage source and produces short electrical pulses when excited into conductance by short first laser light...http://www.google.es/patents/US4896109?utm_source=gb-gplus-sharePatente US4896109 - Photoconductive circuit element reflectometer
