Miniaturized Polarization Splitter Monolithically Integrated With Photodetector

A novel scheme to monolithically integrate photodetectors with a polarization beam splitter (PBS) based on the dielectric transmission gratings is proposed. In this letter, we demonstrate the InP-based two-quadrant photodetector covered over with silicon nitride grating, which serves as both an efficient vertical coupler and a polarization splitter were integrated in a single device. Polarization-diversity detection can be achieved by the grating-based PBS to couple the TE and TM polarized lights into two sets of two-quadrant photodetector. The PBS was designed using the modal method and a numerical simulation method. The simulation results show that the efficiencies of 61% for TE polarized light and 85% for TM polarized light can be coupled into the two sets absorption layers of the two-quadrant photodetector and the polarization crosstalk is -21 and -23, respectively. Since the length of the miniaturized device is only 35μm , it can be suitably employed in the compact polarization-diversity detection modules.