February Fourier Talks 2008

Application of Classical Beams of Orbital Angular Momentum Radiation

The recognition in the early 1990s that light beams could possess Orbital Angular Momentum (OAM) as well as spin angular momentum (polarization) has led to a flurry of both experimental and theoretic research activity. The result has been a remarkable series of technical advances that now enable the routine generation, manipulation and measurement of intense beams of light possessing well-defined and well-controlled OAM characteristics. A number of early experiments involving so-called optical spanners demonstrated that classical OAM light beams could rotate microscopic particles, thus conclusively showing such beams possess OAM. The successful measurement of single photon OAM in 2002 resulted in a strong theoretical research focus on the novel quantum mechanical properties of such photons. Besides the aforementioned optical spanners and high information-density communication, the preponderance of experimental work is also now squarely in the few-photon domain. While it is well known that the spin of a single photon is quantized (σ = ± h), this property is seldom needed or exploited by the defense signal processing practitioners. Rather, the vast majority of defense applications occur firmly in the classical limit where only the statistical ensembles of extremely large numbers of photons are meaningful. Our presentation extends this analogy by identifying a broad collection of tactical defense sensor and signal processing problems where classical OAM photon beams may offer unique solutions.

Joint work with A. D. Greentree and W. Moran, Melbourne.