Study of Ultrafast Semiconductor Photoswitches for CW RF Signal Sampling and Modulation

We present a study of the mixing of a radio frequency (RF) signal and a modulated optical beam, resulting from the beating of two CW lasers, using a photoconductive switch as mixer. The mixing process generates sideband frequencies in the RF transmitted signal. The theoretical analysis gives the performance of the device versus its main physical parameters. The device, if made from ultrafast semiconductors, can handle RF or/and optical beating frequencies up to 100 GHz. When dc biased, the device serves as an optoelectronic generator of RF signal. Our analysis is experimentally validated in the RF range up to 40 GHz using a low-temperature grown GaAs device excited by two laser diodes at 0.8-μm wavelength.