Guided-mode resonance with reduced bandwidth in mid-infrared absorption and thermal emission

Narrowband resonance plays an important role in many optical applications, especially for the development of wavelength-selective properties and enhanced light-matter interaction. In this paper, we demonstrate metal-insulator-metal (MIM) waveguide gratings, which exhibit guided-mode resonance (GMR) with reduced bandwidth in mid-infrared absorption and thermal emission. Our fabricated MIM waveguide grating consists of a copper substrate, a lossless ZnSe film, and a top gold stripe grating. Our measurements reveal strong GMRs with a bandwidth of 1.29% of the central wavelength in both mid-infrared absorption and thermal emission spectra. By varying structural parameters of the MIM waveguide grating, strong absorptions and thermal emissions of GMRs are observed and tuned within the 3-5 µm wavelength range. These results manifest the great potential of engineering infrared properties by using GMR and could be useful for spectral control in a variety of infrared devices.