Single-mode waveguide microcavity for fast optical switching.

We investigate the properties of a tunable single-mode waveguide microcavity that is well suited for frequency modulation and switching. The cavity mode has a volume of less than one cubic half-wavelength, and the resonant frequency is tuned by refractive-index modulation. We suggest using a photorefractive effect to drive the device, based on the photoionization of deep donor levels known as DX centers in compound semiconductors. Picosecond on-off switching times are achievable when two of these cavities are placed in series. The resulting switch has the advantages of being compact and requiring as little as 10 pJ of energy of operate.