We evaluate the effect of finite aperture gratings on the spectral and efficiency characteristics of guided-mode resonance filters. A simple analytical model based on the attenuation properties of the waveguide and a fixed length of the grating aperture is developed. The results from this model are in good agreement with experimental filters formed with subwavelength period photoresist gratings and solgel waveguides.

We demonstrate a two-dimensional (2D) polarization-independent resonant subwavelength grating (RSG) in a filter array. RSGs, also called guided mode resonant filters, are traditionally one-dimensional gratings; however, this leads to TE and TM resonances at different wavelengths and with different spectral shape. A 2D grating can remove the polarization dependence at normal incidence, while maintaining the desirable RSG properties of high reflectivity, narrow passband, and low sidebands without ripple. We designed and fabricated 2D gratings with near-identical responses for both polarizations at normal incidence in the telecommunication band. Ninety percent reflectivity is achieved at the resonant wavelengths.

The design and analysis of a dielectric guided-mode resonance filter (GMRF) utilizing a nonlinear material for the waveguide is presented. Small changes to the parameters of a GMRF have a large impact on its resonance. A nonlinear material can provide a small change in the refractive index of the waveguide, altering the resonance of the device and resulting in modulation of the transmitted and reflected output of the filter. Numerical results show that nonlinear switching from 100% transmission to 100% reflection can be accomplished with less than 100 kW/cm(2) using a simple design.

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