The burgeoning usefulness of optical angular momentum

The Third International Conference on Optical Angular Momentum (ICOAM) covers both theory and applications.

Jul 23rd, 2015
John Wallace 720

A beam of light can carry angular momentum in two ways: either via some form of helical wavefront (orbital angular momentum) or via circular or other chiral forms of polarization (spin angular momentum). Uses include optical trapping of microparticles, high-rate data transmission, control of the position and spin rate of micro- and nanostructures, and even simulation of cosmological objects, as well as stellar coronographs.

The complete guide: ICOAM
The study and application of light with angular momentum has grown to the point where the field has its own annual conference: the Third International Conference on Optical Angular Momentum (ICOAM) will be held August 4 to 7, 2015 at the City College of New York (CCNY; New York, NY).

CCNY is where professor Robert Alfano, physicist and founder of the college’s Institute for Ultrafast Spectroscopy, and his group have pioneered research into orbital angular momentum, including better mathematical descriptions of polarization (including spin angular momentum). Chairing the conference will be Alfano, along with Giovanni Milione of NEC Laboratories America (Princeton, NJ and Cupertino, CA), Enrique Galvez of Colgate University (Hamilton, NY), and David Andrews of University of East Anglia (Norfolk, England). On the conference’s scientific advisory committee are many leading names in the field.

FIGURE. Light that is uniformly polarized across a beam can be linearly, elliptically, or circularly polarized (left: red, blue, and green). Light polarized across a beam in a spatially varying manner can take many designed forms (right), including radial, azimuthal, and higher-order polarization (vertical and horizontal black lines are the x and y axes). (Even more-exotic states of polarization could have been depicted by replacing the red arrows on the right with green circles or properly aligned blue ellipses.) Some of these forms of polarization (circular, elliptical, azimuthal, and higher-order) carry angular momentum, while others don’t.

Theory, generation, measurement, and applications
The conference covers both mathematical theory and leading-edge applications of optical angular momentum. The math can get pretty hairy: the three plenary talks for Session 1, covering the fundamentals, are titled “The azimuthal component of Poynting’s vector”; “Field-theory revolution for optics: Revisiting momentum and angular momentum of light”; and “Optical curl forces and beyond.”

Session 2 covers techniques of generation and measurement of optical angular momentum, with plenaries titled “Generation of structured light and surface plasmon polaritons using Metasurfaces”; “q-plates and their applications: an overview”; “Manipulating structured light”; and “Measuring novel optical phenomena at the nanoscale -- full vectorial field reconstruction of highly confined light beams.”

The topic of Session 3 is structured light, with plenary talks that include “Spatially-structured photons: how fast do they go?”; “Generalised angular momentum”; “Complete conical wave description for the transverse structure of Laguerre-Gauss beams with orbital angular momentum”; “What ray optics can tell us about self-similar optical fields”; and “Generation of flower-type modes possessing orbital angular momentum.” (Being an optical engineer, I’m especially interested in how ray optics, which don’t have any obvious way of depicting angular momentum, can be applied to this field.)

Many more sessions ensue, including the following (many of which emphasize applications): “Optical Forces”; “Chirality and Selection Rules”; “Nanophotonics”; “Nonlinearities, Topological States, and Scattering”; “Fundamental Tests of Quantum Mechanics”; “Quantum Mechanical Measurements”; “Free Space Optical Communication I”; “Quantum Communication, Cryptography, and Memory”; “Cold Atoms and Bose Einstein Condensates”; “Electron Vortex Beams”; “Remote Sensing”; “Optical Fiber Communication”; and “Free Space Optical Communication II.”

Two poster sessions will also be held.

To find out more about the conference, see http://spie.org/OAM/conferencedetails/optical-angular-momentum?webstatus=f

More in Commentary