Reflection of light from gold coated InP NW arrays*

To optimize light coupling into a plasmonic nanowire (NW) array as a function of incident angle and excitation wavelength, we investigated the reflection of light from two different bare and gold coated InP NW arrays. The NWs in the arrays have a diameter of 180 nm, heights of 2 and 1 micrometers and pitches of 666 and 500 nm. A nominally 10 nm thick gold film was deposited around the NWs to investigate the influence of plasmonic effects. The arrays were irradiated with s- and p- polarized light. The spectral reflectance was measured with an incandescent light source ranging from 500 to 1000 nm and the angle resolved reflectance was investigated with a cw laser at 880 nm. The p-polarized angle resolved reflectance of gold deposited NW arrays significantly differs from the reflectance of uncoated InP NW arrays. The differences are attributed to surface plasmon polariton effects. The measured spectrally and angle resolved reflectance was compared with finite-difference-time-domain (FDTD) simulations. The simulations show very good agreement when an air-gold effective medium according to the granularity of the deposited gold films was used.