Polarization-controlled orbital angular momentum switching in nonlinear wave mixing

Abstract

We demonstrate polarization-controlled switching of the orbital angular momentum (OAM) transfer in nonlinear wave mixing. By adjusting the input beam geometry, we are able to produce a three-channel orbital OAM, with arbitrary topological charges simultaneously generated and spatially resolved in the second-harmonic wavelength. The use of path and polarization degrees of freedom allows nearly perfect optical switching between different OAM operations. These results are supported by a theoretical model showing very good agreement with the experiments.

Conditions for optical parametric oscillation with a structured light pump

“…(27) will introduce restrictions on the radial indexes of the modes, depending on the relative signs of the topological charges being added. This kind of cross-talk between radial and angular degrees of freedom has already been investigated in nonlinear OAM mixing [32,33]. All these results are summarized in Fig.4 for the different paraxial bases.…”

“…8, which describes one or a combination of two of the listed down-conversion processes, restricted to an idler beam in a pure Hermite-Gauss mode and order conservation. For example, the first row corresponds to process (33); the second row, to process (35); the third row, to a combination of processes (33) and (35); and finally, the fourth row, to a combination of processes (34) and (38). We present in Fig.9 with the transverse modes with the optimal overlap with it.…”

Optical vortex production mediated by azimuthal index of radial polarization

“…Radial and azimuthal polarizations can interact with the OAM of the light. In previous works, it has been reported the interaction of polarization azimuthal index with OAM under tight focusing conditions [17], the radial to azimuthal polarization conversion using high-order vortices and tight focusing [18], decomposition of linearly polarized vector beams without vortex structure into two orthogonal vortex fields, each one exhibiting OAM with opposite charge m [19], the production of spatially separated OAM modes by geometry, polarization and nonlinear process control [20], the use of polarization azimuthal index to detect OAM under tight focusing [21], and transformation of perturbated polarization singularities into topological charges [22]. Also, diffractive optical elements have been applied to radially polarized beams to spatially separate circularly polarized vortices with opposite helicity [23] and, very recently, it has been measured the spatial phase of vector beams decomposed in vortex beams with circular polarization [24].…”

Tunable vector-vortex beam optical parametric oscillator

“…Moreover, one can actively control the generation of such scalar optical vortices in the signal and/or idler depending upon the loss parameter 17,22 in OPO systems and also controlling the symmetry of OAM in a driven OPO 23 . On the other hand, efforts have been made to generate OAM at different wavelengths through various nonlinear processes 24–28 including second-harmonic-generation (SHG), sum-frequency-generation, high-harmonic-generation, and optical parametric generation using both birefringence-phase-matching and quasi-phase-matching techniques and control the OAM in SHG process by selective choice of the input polarization of the pump beam 29 . Using OPOs providing scalar vortex beams, one can, in principle, manipulate the polarization of the intracavity field to generate vector-vortex beams directly from OPOs.…”