Fully-structured light, light with non-uniform intensity, phase and polarization, lies at the heart of an extremely promising field of research, with applications in high-resolution imaging and optical trapping and manipulation of nanoparticles. Such fields are readily constructed from superpositions of two orthogonally polarized Laguerre-Gaussian modes carrying different orbital angular momentum (OAM). This opens new possibilities in engineering complex light distributions for specific applications.
We simulate the propagation of fully-structured light in a self-focusing nonlinear medium using a coupled two-dimensional nonlinear Schrödinger equation with saturable self-focusing nonlinearity and show that the spatial structure of the polarization can be used to control both the collapse dynamics of the beams [1] and the amount of polarisation rotation. These findings provide a novel approach to transport high-power light beams in nonlinear media with controllable distortions to their spatial structure and polarization properties.
Complex light can also have non-uniform helicity density and the resultant gradients in helicity density will generate a force that will interact differently with opposite enantiomers of chiral molecules [2]. Here we demonstrate how the energy and helicity gradients in the fields, and the corresponding dipole and chiral forces, can be engineered for specific applications. We also investigate the use of nonlinearity to control and manipulate the spatially-varying chiral force.
[1] F. Bouchard et al., Phys. Rev. Lett 117, 233903 (2016)
[2] R. Cameron et al., New J. Phys. 16, 013020 (2014)
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