CRITERIA FOR SHORT OPTICAL DIRECTIONAL COUPLERS IN GaAs-TECHNOLOGY.

For further progress in Integrated Optics based on semiconductor materials directional couplers with coupling lengths as short as possible are required. Using MBE and advanced RIE etch processes maximal attainable refractive index steps are obtained. This is essential for reducing the coupling length. Coupling lengths down to 1. 8 mm for GaAs-homostructure devices have been realized. As a quality criterion besides the optical attenuation the difference of the optical insulation and the theoretical optimum is used. Fabricated GaAs-directional couplers differ about 3 dB from this value.