title: Concurrent spatial and spectral filtering by resonant nanogratings.
abstract: Optical devices incorporating resonant periodic layers constitute an emerging technological area. Recent advances include spectral filters, broadband mirrors, and polarizers. Here, we demonstrate concurrent spatial and spectral filtering as a new outstanding attribute of this device class. This functionality is enabled by a unique, near-complete, reflection state that is discrete in both angular and spectral domains and realized with carefully-crafted nanogratings operating in the non-subwavelength regime. We study the pathway and inter-modal interference effects inducing this intriguing reflection state. In a proof-of-concept experiment, we obtain angular and spectral bandwidths of ~4 mrad and ~1 nm, respectively. This filter concept can be used for focus-free spectral and spatial filtering in compact holographic and interferometric optical instruments.
authors.forename: Manoj
authors.initials: M
authors.lastname: Niraula
authors.forename: Jae Woong
authors.initials: JW
authors.lastname: Yoon
authors.forename: Robert
authors.initials: R
authors.lastname: Magnusson