Structured Light from Lasers

Abstract

Structured light is derived from the ability to tailor light, usually referring to the spatial control of its amplitude, phase, and polarization. Although a venerable topic that dates back to the very first laser designs, structuring light at the source has seen an explosion in activity over the past decade, fuelled by a modern toolkit that exploits the versatility of diffractive structures, liquid crystals, metasurfaces/metamaterials, and exotic laser geometries, as well as a myriad of applications that range from imaging, microscopy, and laser material processing to optical communication. Here, the recent progress in creating and controlling structured light is reviewed, with particular emphasis on structuring light at the source: structured light lasers. The various design approaches, including pump shaping, cavity geometries, and the use of custom intracavity optical elements, implemented in a variety of lasers from microchip solutions to high‐power fibers are covered in a tutorial style. The history and latest developments in the field are reviewed, elucidating the various structured light patterns that have been created from lasers, including orbital angular momentum and vector states of light. Finally, the present challenges and limitations are highlighted, along with comments on likely future trends.

Creation and control of high-dimensional multi-partite classically entangled light

“…Spatial light mode control in lasers allows one to specify the desired modal amplitude, phase and polarisation 15 . While the spatial modes usually refer to the eigenmodes of the paraxial wave equation, there is also a class of complex spatial wave-packet modes that possess a geometric interpretation with SU(2) symmetry, a general symmetry for describing paraxial structured beams with OAM evolution mapped on a Poincaré-like sphere 69 .…”

“…Sharing the same hallmark of non-separability of quantum entanglement, the classically entangled vector beam is more than simple mathematical machinery and can extend a myriad of applications with quantum-classical connection. Such states of vectorially structured light have been created external to the source through interferometric approaches by spin–orbit optics 11 – 14 , as well as by customised lasers 15 including custom fibre lasers 16 , intra-cavity geometric phase elements in solid-state lasers 17 – 20 and custom on-chip solutions 21 – 23 . The resulting beams have proved instrumental in imaging 24 , optical trapping and tweezing 25 , 26 , metrology 27 – 29 , communication 30 , 31 and simulating quantum processes 8 – 10 , 32 – 36 .…”

Artificial neural networks for inverse design of resonant nanophotonic components with oscillatory loss landscapes

“…Our technique will be particularly valuable for inverse design of optical components based on many nanophotonic resonators, such as coupled or multi-layered resonators [28][29][30], lasers [31], dispersion-engineered metasurfaces [32] and (nonlinear) resonators in the context of integrated optics [33,34]. Finally, because this method can incorporate several parameters of the incident light, we think it will be interesting to study and optimize complex materials interacting with structured light beams [35][36][37][38][39].…”

Structured Light in Turbulence

“…These so-called structured light fields [35][36][37] hold tremendous potential, but there is a limitation: spatial modes of light are not impervious to distortion, and in particular they are adversely affected by atmospheric turbulence. Scattering of one mode into another increases noise, reducing classical channel capacity due to modal cross-talk [38][39][40][41][42] and reducing security and/or entanglement in a quantum link [43][44][45][46][47][48][49][50][51][52].…”