The RCE detectors are constructed by integrating a thin absorption region into an asymmetric Fabry-Perot cavity formed by a bottom mirror composed of a distributed Bragg Reflector and the semiconductor air interface. Quantum efficiency of these RCE devices can be controlled by tuning the cavity length by recessing the top surface of the detector. A pair of monolithically integrated RCE photodetectors with cavity lengths tuned for resonance and anti-resonance provide a large contrast in response to TE and TM polarizations. The device formed by this technique eliminate the need for external polarization filters and beam splitters, thus alleviating the problems associated with the bulkiness of the polarization sensors in many applications.
Polarization sensing typically involve polarizing filters or beam splitters.
It is desirable to eliminate the bulky optical components and integrate polarization selectivity and detection in a single device structure. The RCE structure consists of a thin absorption region placed in an asymmetric Fabry-Perot cavity. The RCE devices benefit from the wavelength sensitivity and the large increase of the resonant optical field introduced by the cavity resulting in high quantum efficiencies without requiring thick absorption regions. If the light incidence is at an angle with the normal, L is replaced by . When the optical length of the cavity satisfies the resonance condition, the cavity enhances the optical fields and the detector response is drastically increased.