Efficient Polarization Diversity Grating Couplers in Bonded InP-Membrane

We report on the design, fabrication, and measurement of compact and efficient grating couplers between fiber and nanophotonic waveguides, in a polarization diversity configuration. This approach allows for polarization-independent integrated circuits. The gratings and waveguides are fabricated in a benzocyclobutene (BCB)-bonded InP-membrane, with high vertical refractive index contrast. The coupling loss of the gratings is 3.3 dB and the measured polarization-dependent loss is 0.79 dB.