Orbital angular momentum sidebands in second harmonic generation of a vortex beam by a nonlinear crystal with inhomogeneous refractive index

Abstract

The manipulation of the orbital angular momentum (OAM) spectrum in new wavelengths generated by frequency conversion has a wide range of applications in quantum information technology and modern communications. Here, the second harmonic generation of a vortex beam in a nonlinear crystal with an inhomogeneous refractive index is considered. It is shown that by using a segmented oven and generating a controllable temperature gradient along the thickness of the nonlinear crystal, a transverse phase mismatch can be induced in the vortex beam. Accordingly, the OAM spectrum of the vortex beam can be changed by generating new OAM components in the spectrum. Compared with the nonlinear Bragg diffraction method, the presented method has the advantage of longer interaction length and higher efficiency.