A study of novel mid-infrared optical devices: wave plates and tunable filters

Abstract

The mid-infrared wavelength range is important for both molecular sensing and thermal imaging. However, many optical devices that are common in the visible range are not as accessible in the mid-infrared. In this thesis, we look to partially address this problem by proposing two novel structures using subwavelength gratings. First, we look at a wave plate design that uses a physical path length difference to impose a phase shift between the components of incident light as an alternative to costly birefringent crystals. Then, we look at a crossed grating structure that serves as a narrowband filter due to its extraordinary transmission. We also propose a way to make the filter structure actively tunable.