We investigate the properties of a tunable single-mode waveguide micro
cavity 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 sug
gest using a photorefractive effect to drive the device, based on the
photoionization of deep donor levels known as DX centers in compound s
emiconductors. Picosecond on-off switching times are achievable when t
wo of these cavities are placed in series. The resulting switch has th
e advantages of being compact and requiring as little as 10 pJ of ener
gy of operate. (C) 1996 Optical Society of America.