PROCEEDINGS ARTICLE | March 5, 2013

Proc. SPIE. 8637, Complex Light and Optical Forces VII

KEYWORDS: Superposition, Laser sources, Holograms, Digital holography, Spatial light modulators, LCDs, Bessel beams, Phase measurement, Modes of laser operation, Phase shifts

By using digital holograms, we present a simple technique for performing a complete azimuthal decomposition of an
arbitrary laser mode. The match-filter, used to perform the azimuthal decomposition, is bounded by an annular ring,
allowing us to conduct a scale-independent decomposition on our selected mode. This technique therefore requires no
prior knowledge of the mode structure, the mode phases, or the amplitude distribution. A basis comprising of the angular
harmonics is used to express the spatial distribution of the selected mode in terms of spatially dependant coefficients. We
use this to infer directly from the measured weightings of the azimuthally decomposed modes and their phase-delay
measurements, the intensity of the selected field, its phase, and its orbital angular momentum (OAM) density. We
illustrate the concept by executing a full decomposition of two examples: a superposition of two Bessel beams, with
relative phase differences, and an off-axis vortex mode. We show a reconstruction of the amplitude, phase and OAM
density of these fields with a high degree of accuracy.