Abstract View
Single Particle Light Scattering from Light Beams with Orbital Angular Momentum
MATTHEW B. HART, Vasanthi Sivaprakasam, Ryan Lindle, Wenbo Sun, Abbie Watnik, Naval Research Laboratory, Washington, DC
Abstract Number: 685
Working Group: Aerosol Physics
Abstract
The solution to Maxwell’s equations includes light with an angular component of momentum with respect to the direction of propagation. That is, the Poynting vector of this type of light, which defines the energy flux, has an angular component. Such light is commonly referred to as having orbital angular momentum (OAM). The solution of Maxwell’s equation describing this light includes the Associated Laguerre polynomials, Lnm, which result in OAM beams for all n or m > 0, and Gaussian light for n = m = 0. For all cases where m ≠ 0, OAM beams will have an intensity minima along the central axis of the beam. This, together with the angular component of the energy flux, can cause the scattering interactions with materials to be very different than that from plane waves. Theoretical angular scattering calculations show that the light scattering maxima occur at different angles from the forward direction of zero degrees [1, 2]. The use of OAM light is being explored in a wide range of fields that include material interrogation, light propagation, sensing and communication.
In this work we investigate the scattering properties of OAM light from single, micron sized spherical particles that are suspended in an electrodynamic trap that we optimized for a previous study [3]. We utilize phase plates and a spatial light modulator to generate the OAM beams (wavelength of 532 nm) that are incident on a suspended particle. We have adapted the particle trap to study the angle resolved scattering signal in a scattering plane that covers over 40 degrees in each of the forward, back and side scattering geometries. We plan to generate OAM beams of varying mode (m = 0 to 8) and collect the angular scattering signal for varying sizes of commercially available particles of varying materials. Preliminary angular scattering calibration measurements from Gaussian beams and varying order OAM modes will be presented. Our future plans and comparison to theoretical measurements will be discussed.
[1] W. Sun, Y. Hu, C. Weimer, K. Ayers, R. R. Baize, and T. Lee, "A FDTD solution of scattering of laser beam with orbital angular momentum by dielectric particles: Far-field characteristics," Journal of Quantitative Spectroscopy and Radiative Transfer 188, 200–213 (2017).
[2] A. W. Jantzi, M. G. Cockrell, L. K. Rumbaugh and W. D. Jemison, "Mixed numerical and analytical method for investigating orbital angular momentum beam scattering in turbid water," Opt. Eng. 58, 1 (2019).
[3] M. B. Hart, V. Sivaprakasam, J. D. Eversole, L. J. Johnson, and J. Czege, "Optical measurements from single levitated particles using a linear electrodynamic quadrupole trap," Appl. Opt. 54, F174 (2015).