This paper presents a narrow spectral filter based on a monolithic material system. Guided-mode resonance is achieved by embedding a periodic array of air holes within a similar-index material. Microvoids created in the lowindex substrate during deposition of the waveguide give a relatively high index contrast for guided-mode resonance. One and two-dimensional gratings are used to examine polarization dependence of the device. Theoretical and experimental results are provided, demonstrating a roughly six nanometer resonance at the full width half-maximum for both geometries.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.