Direct Generation of Vortex Laser Beams and Their Non-Linear Wavelength Conversion

Abstract

Vortex laser beams are a technology that has revolutionised applications in micro-and nano-manipulation, micro-fabrication and super-resolution microscopy, and is now heralding advances in quantum communication. In order to service these, and emergent applications, the ability to generate powerful vortex laser beams with user-controlled spatial and wavefront properties, and importantly wavelength, is required. In this chapter, we discuss methods of generating vortex laser beams using both external beam conversion methods, and directly from a laser resonator. We then examine the wavelength conversion of vortex laser beams through non-linear processes of stimulated Raman scattering (SRS), sum-frequency generation (SFG), second harmonic generation (SHG) and optical parametric oscillation. We reveal that under different types of non-linear wavelength conversion, the spatial and wavefront properties of the vortex modes change, and in some cases, the spatial profile also evolve under propagation. We present a theoretical model which explains these dynamics, through decomposition of the vortex mode into constituent Hermite-Gaussian modes of the laser resonator.

Recent Progress in Nonlinear Frequency Conversion of Optical Vortex Lasers

“…Nevertheless, another technique for filling in the wavelength gap is by nonlinear frequency conversion. In 2017, Omatsu et al [91] and Lee at al [92] have respectively made reviews in this regard, with special attention to their work in this area. However, in the last 5 years, there have been many new achievements in nonlinear frequency conversion of OAM-carrying optical vortices.…”