Thick Volume Holograms for Polychromatic Wavefront Selection

Abstract

Presented is the theoretical basis and empirical evidence for a spatial-spectral holographic filtration system, referred to as the Advanced Volume Holographic Filter (AVHF), allowing for the discrimination of polychromatic wavefronts by range. State-of-the-art volume hologram-based imaging systems (VHIS) make use of a single, thick holographic grating as a spectral/spatial transmittance filter, allowing for depth-based, narrowband wavefront selection. However, imaging polychromatic sources at range using VHIS results in the loss of retrievable spectral information. Herein an optical system consisting of two coupled holographic elements is presented, with aims to increase the spectral bandwidth capabilities of the current volume hologram-based filtering approaches while maintaining range-based wavefront selectivity. Briefly, the AVHF is composed of a thin-volume hologram functioning as a pre-dispersive element used to Bragg match the spectra of an incoming wavefront onto a thick-volume hologram capable of depth-based wavefront selection. Our laboratory proof of concept demonstrated a resolvable spectral bandwidth increase from <1 nm using the single element VHIS method to ∼100 nm using the AVHF filter whilst maintaining the stringent VHIS spatial-selectivity performance for depth-based wavefront selection