Carrier-injected GaInAsP/InP directional coupler optical switch with both tapered velocity and tapered coupling

For most applications, a quasi-digital switching response is desired. The authors report on the design and fabrication of a 2*2 ´digital´ optical switch in GaInAsP/InP based on a directional coupler with both tapered velocity and tapered coupling and designed to be in the cross state at the zero bias condition. Complete power transfer to the cross output port for both TE and TM polarizations has been realized in the passive couplers for a wide range of device lengths proving the theoretically predicted fabrication tolerances. In the very first controllable device, switching operation with a crosstalk of -7 dB has been achieved using carrier injection.<>