PROPOSAL OF SEMICONDUCTOR DIRECTIONAL-COUPLER-TYPE ALL-OPTICAL SWITCHWITH TAPERED-WAVE-GUIDE STRUCTURES

We propose a semiconductor directional-coupler-type all-optical switch with tapered structures which is based on the nonlinear refractive in dex variation induced by photoexcited carriers. A recurrence equation describing the device is derived from ''Marcatili's'' coupling mode th eory and studied by numerical simulations. It is shown that the introd uction of tapered structures is effective for improving the extinction ratio. It is also found that this device can drive a signal light at a power about 17dB higher than the control light power.