Switchable distributed Bragg reflector using GST phase change material

Recent developments in Chalcogenide phase change material-based nanophotonics

There is now a deep interest in actively reconfigurable nanophotonics as they will enable the next generation of optical devices. Of the various alternatives being explored for reconfigurable nanophotonics, Chalcogenide phase change materials (PCMs) are considered highly promising owing to the nonvolatile nature of their phase change. Chalcogenide PCM nanophotonics can be broadly classified into integrated photonics (with guided wave light propagation) and Meta-optics (with free space light propagation). Despite some early comprehensive reviews, the pace of development in the last few years has shown the need for a topical review. Our comprehensive review covers recent progress on nanophotonic architectures, tuning mechanisms, and functionalities in tunable PCM Chalcogenides. In terms of integrated photonics, we identify novel PCM nanoantenna geometries, novel material utilization, the use of nanostructured waveguides, and sophisticated excitation pulsing schemes. On the meta-optics front, the breadth of functionalities has expanded, enabled by exploring design aspects for better performance. The review identifies immediate, and intermediate-term challenges and opportunities in (1) the development of novel chalcogenide PCM, (2) advance in tuning mechanism, and (3) formal inverse design methods, including machine learning augmented inverse design, and provides perspectives on these aspects. The topical review will interest researchers in further advancing this rapidly growing subfield of nanophotonics.

Multiplexed digital volume reflection holograms generated from digital transmission holograms

Interference from co-propagation of the object and reference beams can be digitally recorded for a digital transmission hologram (DTH). Volume holograms, as in display holography, which have been traditionally recorded in bulk photopolymer or photorefractive materials using a counter-propagating object and writing beams, are read out using multispectral light and offer the advantage of excellent wavelength selectivity. In this work, the reconstruction from a single digital volume reflection hologram (DVRH) and wavelength multiplexed DVRHs derived from respective single and multi-wavelength DTHs is investigated, using coupled wave theory and an angular spectral approach. The dependence of the diffraction efficiency on volume grating thickness, wavelength, and incident angle of the reading beam is studied.