Longwave infrared polarization independent monolithic guided-mode resonance filters with double-sided orthogonal linear gratings

Abstract

We present novel polarization independent, high-quality monolithic spectral filters based on the guided-mode resonance (GMR) effect with orthogonal linear gratings on either side of the substrate operating in the longwave infrared (LWIR) spectral region. We employ high-spatial resolution e-beam lithography and reactive-ion etching (RIE) nanofabrication techniques to achieve large-area (10×10 mm2) notch filters with subwavelength features. We fabricated prototype filters and characterized their polarization independent spectral performance with both coherent and incoherent incident light using a tunable quantum cascade laser (QCL) system that spans the ∼8–12 µm spectral band as well as a Fourier transform infrared (FTIR) spectrometer with collimated incident beam.