Polarization Conversion of Light Diffracted from InP Nanowire Photonic Crystal Arrays

This work investigates the polarization state of light diffracted from uncoated and gold-coated InP nanowire photonic crystal arrays grown by selective area epitaxy. Experimental data and finite-difference time-domain simulations show that both the intensity and the ellipticity of the polarization state of the diffracted light beam can be controlled by the nanowire dimensions and gold coating, while the diffracted angle remains unchanged with respect to variations of these parameters. A nominally 10 nm-thick gold film deposited around the nanowires enhances the diffraction intensity by plasmonic effects. These results demonstrate that the controlled conversion of incident linearly polarized light to circularly polarized or rotated linearly polarized diffracted light can find applications in photonic integrated circuits. The high sensitivity of the polarization state with respect to alterations of the nanowire dimension opens new prospects in the areas of semiconductor metrology and microchip inspection as well as for submicron particle detection.