POLARIZATION SENSING WITH RESONANT-CAVITY ENHANCED PHOTODETECTORS

We describe a new method of sensing the linear polarization of light u sing resonant cavity enhanced (RCE) photodetectors. The RCE detectors are constructed by integrating a thin absorption region into an asymme tric Fabry-Perot cavity. The top reflector is formed by the semiconduc tor air interface, while the bottom mirror is a distributed Bragg refl ector (DBR). Quantum efficiency of these RCE devices can be controlled by tuning the cavity length by recessing the top surface of the detec tor, For off-normal incidence of light, the reflectivity of the semico nductor-air interface can be significantly different for TE(s) and TM( p) polarizations, A pair of monolithically integrated RCE photodetecto rs with cavity lengths tuned for resonance and antiresonance provide a large contrast in response to TE and TM polarizations, An alternative polarization sensor can be formed by vertically integrating a convent ional and a RCE photodetector, We show that a large contrast in the TE /TM responsivities of the vertical cavity polarization detectors (VCPD ) can be achieved, thus combining detection and polarization sensing i n a single mesa semiconductor device. These devices alleviate the prob lems associated with the bulkiness and critical alignment constraints of the conventional sensors based on polarizing filters or splitters a nd have potential for fabrication of monolithic smart pixels and imagi ng arrays.