Guided-wave metal-semiconductor switch for modulation of 10.6 μm radiation

We present a novel optical-optical switching technique for modulation of infrared radiation. The modulation response is based upon the optical perturbation of semiconductor layers within an ah-filled metal-clad semiconductor waveguide. Generation of the electron-hole plasma within these layers is via femtosecond pulses of above bandgap radiation (800nm). The propagation characteristics of this five-layer structure are analyzed through the coupling of quasi-static electromagnetic analysis to the time-varying optical properties of the semiconductor layers. It is found that the device is able to modulate radiation at various frequncies, though we specifically investigate modulation of 10.6 mu m radiation. At this wavelength, an electron-hole photoinjection density of similar to 1 x 10(18) cm(-3) in the semiconductor layers provides an extinction ratio of 30 dB. The significance of this modulation depth and possible applications to all-optical Mach Zehnder metal-clad semiconductor modulators and self-limiting switches are discussed.