Reflection properties of uncoated and gold-coated InP photonic crystals*

We investigated the spectral and angle resolved reflectance of uncoated and gold coated InP nanowire (NW) arrays which were grown by selective area epitaxy. The NW arrays were coated with a 12-nm thick Al₂O₃ film to suppress atmospheric oxidation. An additional 10-nm thick gold film was further deposited around the NWs to investigate plasmonic effects. The arrays reveal pronounced Fabry-Perot oscillations due to their strong intrinsic birefringence, shifted for p- and s-polarized light. Gold-coating of the NW array increases the reflectance by a factor of two to three compared to the uncoated array. This increase is attributed to a plasmon resonance of the gold caps on top of the NWs and to a plasmonic antenna effect for p-polarized light. Both interpretations are supported by finite-difference time-domain simulations. The reflectance of light is highly polarization-dependent, making InP NW PhC arrays ideal micrometer-sized optical elements like polarizers, analyzers, and mirrors with potential applications in photonic integrated circuits.