Generation and characterization of 420 nm vortex bessel beam with tunable orbital angular momentum

This study presents a theoretical exploration of generating 420 nm Bessel-Gaussian beam with orbital angular momentum (OAM) via nonlinear processes in a four-level 85 Rb atomic system. A non-degenerate four-wave mixing (FWM) configuration, driven by two strong control fields at wavelengths 780 nm and 776 nm along with a weak field, enables the generation of the desired blue Bessel-Gaussian beam. Our analysis examines how the Bessel-Gaussian properties of the initial beams including intensity, phase profiles, and topological charges are transferred into the generated 420 nm beam at specific transverse positions. Using Maxwell's wave equations, we explicitly explore how these spatial profiles evolve with varying topological charges over different propagation distances, providing deeper insights into Bessel-Gaussian information transfer mechanisms. The generation and characterization of 420 nm structured beam highlight promising applications, particularly in the precise manipulation of microparticles, due to their enhanced resolution and superior trapping abilities. This comprehensive theoretical framework establishes a foundation for future experimental and applied research in optical manipulation and high-resolution imaging.