Ultra-compact monolithic integration of polarization diversity waveguide photodiodes

Summary form only given. A description is given of a device which consists of an input rib waveguide, a vertically defined coupler, a vertically coupled mesa p-i-n photodiode (PD), a second coupler, and a second PD, all serially connected. A gold cover on the first coupler ensures that only TE-polarized light is coupled into the first PD; the second coupler/PD pair collects the remaining TM light. Component lengths are 79 and 54 μm for couplers and 21 and 31 μm for PDs, for ~200-μm total detector length. The device consists of p-InGaAsP/i-InGaAs/n-InGaAsP PD layers above semi-insulating coupler layers (two GaAsP:Fe guides, InP:Fe cladding). The vertically integrated coupler/detectors are more than an order of magnitude smaller than conventional couplers, and of comparable size to electronic components (e.g. FET gate widths)