Direct fabrication and characterization of high-aspect-ratio plasmonic nanogratings using tapered-sidewall molds

High-aspect-ratio plasmonic nanogratings are promising for applications such as polarimetric infrared (IR) detectors and IR emitters. Direct fabrication using conventional photolithography is necessary for their integration with other semiconductor devices. Nanogrooves with a high aspect ratio of 15 and a width of 100 nm were developed using a tapered-sidewall mold technique. Calculations and experimental measurements demonstrated that they have a strong wavelength- and polarization-selective absorption profile that is defined mainly by the groove depth, and that the FWHM of the absorbance can be controlled by the grating period. This study will contribute to the development of thermal polarimetric imaging and thermal emitters for gas sensing.