Optical signal distribution in waveguide-coupled metal-smiconductor-metal detector arrays

We report the use of waveguide-coupled GaAs metal-semiconductor-metal (MSM) photodetectors for signal distribution in an optoelectronic matrix switch. The power delivered to multiple detectors that are plated in-line on a single AlGaAs waveguide can be balanced by varying the detector lengths along the propagation direction and by controlling the degree of coupling between the waveguiding and absorbing layers. The dependence of the coupling strength on the thicknesses of the absorbing layer and the buffer layer that separates it from the waveguide was modeled numerically. Experimentally, the coupling strength was varied by tuning the operating wavelength across the GaAs band edge. Uniform power distribution among four in-line detectors was demonstrated.