Ultrafast all-optical modulation of infrared radiation via metal-semiconductor waveguide structures

We present a novel optical-optical semiconductor switching technique for ap plication to infrared laser beam modulation and ultrashort infrared laser p ulse switching, This method relies on the ultrafast optical excitation, wit h femtosecond above-bandgap laser radiation, of an air-filled metal-clad se miconductor waveguide. Guided electromagnetic wave analysis combined with t ime-varying dielectric properties of the semiconductor layer are used to in vestigate the ultrafast switching speed of the structure. The device is cap able of modulation at various infrared wavelengths. In particular, we inves tigate intensity modulation of the quasi-TE10 mode for 10.6-mu m laser radi ation, At an electron-hole photoinjection density of similar to 1.8x10(18) cm(-3), an extinction ratio of 83 dB is demonstrated. This ratio is signifi cantly higher than that exhibited by current optical-optical semiconductor switches, Potential applications to all-optical Mach-Zehnder metal-clad sem iconductor modulators and self-limiting switches are also discussed.