VERTICAL MULTIPLE-QUANTUM-WELL DIRECTIONAL-COUPLER SWITCH WITH LOW SWITCHING VOLTAGE

A novel device structure of the vertical directional-coupler optical switch with multiple quantum well (MQW's) is proposed and fabricated. All the clad, guide, and separation layers are superlattices of Al0.3Ga0.7As and GaAs. This leads to a better control of the complete coupling length. The main feature of the proposed structure is that the refractive index modulation due to the quantum confined Stark effect (QCSE) is applied only to the undoped central region of the separation layer. It is found that this leads to reduction of the switching voltage. In an actual sample 138-mu-m long, a switching voltage of 5 V has been obtained.