Creation and detection of optical modes with spatial light modulators

TLDR

Modal decomposition of light has long been used for pattern recognition, and the advent of liquid‑crystal devices and digital holography has made all‑digital light‑decomposition tools widely available. This review surveys recent progress in characterizing light, from laser beam modal structure to decoding information encoded in orbital angular momentum fields. The authors demonstrate how digital holograms can extract intensity, phase, wavefront, Poynting vector, polarization, and OAM density of unknown optical fields, and apply these techniques to fiber lasers, solid‑state lasers, and laboratory‑generated structured light. They show that virtually all ISO‑standard beam diagnostics can be replaced by all‑digital equivalents, enabling real‑time analysis useful for laser systems, mode‑division multiplexing, and quantum information processing.

Abstract

Modal decomposition of light has been known for a long time, applied mostly to pattern recognition. With the commercialization of liquid-crystal devices, digital holography as an enabling tool has become accessible to all, and with it all-digital tools for the decomposition of light have finally come of age. We review recent advances in unravelling the properties of light, from the modal structure of laser beams to decoding the information stored in orbital angular momentum (OAM)-carrying fields. We show application of these tools to fiber lasers, solid-state lasers, and structured light created in the laboratory by holographic laser beam shaping. We show by experimental implementation how digital holograms may be used to infer the intensity, phase, wavefront, Poynting vector, polarization, and OAM density of some unknown optical field. In particular, we outline how virtually all the previous ISO-standard beam diagnostic techniques may be readily replaced with all-digital equivalents, thus paving the way for unravelling of light in real time. Such tools are highly relevant to the in situ analysis of laser systems, to mode division multiplexing as an emerging tool in optical communication, and for quantum information processing with entangled photons.