Torsion pendulum driven by the angular momentum of light: Beth’s legacy continues

Abstract

.The optical angular momentum is ubiquitous to the science of light, especially whenever the polarization state and the spatial distribution of the phase are involved, which are most often associated with the spin and orbital parts of the total angular momentum, respectively. Notably, the independent introduction of these two contributions to the total optical angular momentum was accompanied by suggestions regarding the possible detection of their mechanical effects using a torsion pendulum. Today, the classical and quantum mechanical aspects of spin and orbital angular momentum of light and their mutual coupling remain active research topics offering exciting perspectives for photonic technologies. Our brief historical overview shows how the torsion pendulum has accompanied scientific advances on mechanical effects based on the angular degrees of freedom of light since Beth’s pioneering contribution published in 1935.

Optical orbital angular momentum transfer to electronic currents

“…Beth, in his famous experiment, managed to rotate a birefringent plate with circularly polarized light using parametric amplification [4]. This has since inspired several experiments [5], with a direct evidence of the torque on macroscopic [6] and microscopic objects [7]. Still in electromagnetism, the rotation of objects was also observed using orbital angular momentum (OAM) at the atomic [8], microscopic [9,10] and macroscopic scales [11,12].…”

Deep‐subwavelength characteristics of focused vector double‐petal linear edge dislocation beams

“…25 Singular beams have highly significant applications in optical tweezers, 26,27 optical communications, 28,29 information storage, 30 optical detection and sensing, [31][32][33][34] and many other fields due to their special phase distributions. 35,36 In this work, we focus on the investigation of the double-petal linear edge dislocation (DPLED) beams, which can be obtained by superposing two vortex beams with opposite topological charges. Based on the Richards-Wolf vector diffraction theory, the electric fields after tightly focused are derived.…”

Iso-propagation vortices with OAM-independent size and divergence toward future faster optical communications

“…As delineated by Allen et al 1 in 1992, vortex fields have become a focal point of research in light fields due to their capability to carry orbital angular momentum (OAM). This property has garnered substantial interest across various sectors, encompassing high-dimensional classical and quantum information communications, 2-4 micro-particle manipulation, 5,6 optical measurements, 7,8 optical imaging, 9,10 and processing. [11][12][13] A persistent challenge encountered is light diffraction, which results in increased beam size and divergence as the mode index augments.…”