POLARIZATION SENSING WITH RESONANT-CAVITY ENHANCED PHOTODETECTORS

The authors describe a new method of polarisation sensing using resona nt cavity enhanced (RCE) photodetectors. The RCE. detectors are constr ucted by integrating a thin absorption region into an asymmetric Fabry -Perot cavity formed by a bottom mirror composed of a distributed Brag g Reflector and the semiconductor air interface. Quantum efficiency of these RCE devices can be controlled by tuning the cavity length by re cessing the top surface of the detector. For off-normal incidence of l ight, the reflectivity of the semiconductor-air interface can be signi ficantly different for TE (s) and TM (p) polarisations. A pair of mono lithically integrated RCE photodetectors with cavity lengths tuned for resonance and anti-resonance provide a large contrast in response to TE and TM polarisations. The device formed by this technique eliminate s the need for external polarisation filters and beam splitters, thus alleviating the problems associated with the bulkiness of the polarisa tion sensors in many applications.