Optical Fourier Volumes: A Revisiting of Holographic Photopolymers and Photoaddressable Polymers

Abstract

To avoid mixing of the undesired frequencies in a free-space, the point sources of gratings, defined by a spatially varying refractive index, should be sinusoidally rather than binarily arranged. This long-lasting but gold standard lesson attainable from a classical Fourier optics, however, is underutilized in the practical materialization of gratings, mainly because most of the fabrication methods, developed thus far, are intrinsically compatible with a binary rather than sinusoidal grating. Recently, such design concept of optical Fourier elements has been implemented into the real surface gratings (referred to as optical Fourier surfaces) by taking advantage of advanced nanofabrication, whereas their volumetric equivalents (optical Fourier volumes, OFVs) have yet to be conceptually and experimentally elucidated. In this work, the key characteristics of OFVs and their structural requirements are systematically exploited with the assistance of analytical and numerical calculations. Especially, the dynamic range and thickness of volume gratings, required for OFVs, are newly defined. Given these theoretical blueprints, both the holographic photopolymers and photoaddressable polymers are then revisited and they are experimentally validated as easy-to-craft mediums of OFVs. The landscape of volume gratings is extended by providing an integrative pipeline of OFVs across their theoretical design and practical materialization.