Waveguide-detector couplers for integrated optics and monolithic optoelectronic switching arrays

An integrated waveguide-detector coupler (IWDC), in which a controlled fraction of the optical power in a waveguide is selectively coupled to a detector element, has been investigated. The device structure consists of a rib waveguide formed from a sputtered Corning 7059 glass film on an oxidized silicon substrate. A photoconductive detector is fabricated on the same substrate, and the degree of coupling is controlled by tapering the SiO(2) cladding layer thickness in the region between the electrodes and by varying the interaction length. Couplers with cladding layer thicknesses ranging from 0.15 to 0.80 microm in the detector interaction region were measured to have coupling values from 400 to 1500 dB/cm for TE modes and to 5800 dB/cm for TM modes, in good agreement with theory. The first integrated optoelectronic 2 x 2 switching matrix using IWDCs as switching cross-points has been demonstrated. We have shown that the passive power splitting in the integrated switch is nearly the ideal 50%.