Unique reflection from birefringent uncoated and gold-coated InP nanowire crystal arrays

We demonstrate unique reflective properties of light from bare and gold-coated InP nanowire (NW) photonic crystal arrays. The undoped wurtzite InP nanowire arrays are grown by selective area epitaxy and coated with a 12-nm thick Al₂O₃ film to suppress atmospheric oxidation. A nominally 10-nm thick gold film is deposited around the NWs to investigate plasmonic effects. The reflectance spectra show pronounced Fabry-Perot oscillations, which are shifted for p- and s-polarized light due to a strong intrinsic birefringence in the NW arrays. Gold-coating of the NW array leads to a significant increase of the reflectance by a factor of two to three compared to the uncoated array, which is partially attributed to a plasmon resonance of the gold caps on top of the NWs and to a plasmonic antenna effect for p-polarized light. These interpretations are supported by finite-difference-time-domain simulations. Our experiments and simulations indicate that NW arrays can be used to design micrometer-sized polarizers, analyzers, and mirrors which are important optical elements in optoelectronic integrated circuits.