Optical response of micron period metal lamellar gratings

We present a theoretical and experimental examination of the optical response of micron and submicron metal lamellar transmission gratings to visible and infrared radiation. Furthermore, we illustrate for the first time the importance of diffraction for the coupling of light into optoelectronic devices incorporating such gratings. This study was made possible by recent advances in vector grating theory and materials processing capabilities.; We apply a coupled wave analysis to the specific geometry of gold lamellar transmission gratings in vacuum and on GaAs substrates to obtain a rigorous, quantitative solution for grating response in the visible and near infrared. Features consistent with the wire grid polarizer effect, Rayleigh resonances, and geometric optics, are recovered in the appropriate limits. Losses to the metal, which had been neglected in prior studies, are shown to be as large as 80% of the incident optical power. Absorption in the metal and substrate (associated with complex refractive indices) is shown to lead to a broadening and reduction in amplitude of Rayleigh wavelength resonance features in the transmission efficiency, and a reduction in the extinction between orthogonal polarizations in the wire grid polarizer limit.; Measurements of the transmission efficiency of metal-semiconductor-metal photodetectors, which are fabricated on GaAs substrates and incorporate a periodic electrode structure, are performed for visible (substrate is absorbing) and infrared (substrate is transparent) radiation. The results of these measurements are used to demonstrate the rigorous nature of the analysis and to establish practical limits for the application of an infinite grating approximation to model finite structures.; We also demonstrate a previously unreported polarization dependence of submicron period metal-semiconductor-metal photodetector response to 110 fs pulsed optical excitation which is enhanced above the polarization dependence of the optical transmission efficiency of the electrodes. The coupled wave analysis is used to obtain a detailed picture of the optical field and photoexcited carrier distributions in the GaAs substrate and explains the enhancement as the manifestation of near field optical effects associated with surface electromagnetic waves. A refined model of photodetector response, which incorporates physical optics effects, is presented.