Non-linear unbalanced Bessel beams: Stationary conical waves supported by nonlinear losses

Underlying conservation and stability laws in nonlinear propagation of axicon-generated Bessel beams

In light filamentation induced by axicon-generated, powerful Bessel beams, the spatial propagation dynamics in the nonlinear medium determines the geometry of the filament channel and hence its potential applications. We show that the observed steady and unsteady Bessel beam propagation regimes can be understood in a unified way from the existence of an attractor and its stability properties. The attractor is identified as the nonlinear unbalanced Bessel beam (NL-UBB) whose inward Hänkel beam amplitude equals the amplitude of the linear Bessel beam that the axicon would generate in linear prop…

单自由传播贝塞尔光束中被动的横基模转换

Passive Cross-Basis Mode Transitions Along a Single Freely Propagating Bessel Beam

该研究展示了如何通过单个自由传播的贝塞尔光束中的径向位置与轴向重建距离的一一映射，将静态相位-only空间光调制器的径向孔径转换为可编程的纵向模式寄存器，从而实现离散的横模编码。

Experimental measurement of the self-healing of the spatially inhomogeneous states of polarization of radially and azimuthally polarized vector Bessel beams

We experimentally measured the self-healing of the spatially inhomogeneous states of polarization of radial and azimuthal polarized vector Bessel beams. Radial and azimuthal polarized vector Bessel beams were generated via a digital version of Durnin's method, using a spatial light modulator in concert with a liquid crystal $q$-plate. As a proof of principle, their intensities and spatially inhomogeneous states of polarization were measured using Stokes polarimetry as they propagated through two disparate obstructions. It was found, similar to their intensities, the spatially inhomogeneous sta…

Theoretical and numerical investigation of internal conical refraction of structured light beams

We present an ab-initio numerical investigation of the internal conical refraction of structured light beams in a biaxial crystal. Starting from the solutions of the Fresnel equation, a theoretical analysis is developed without assuming any analytical approximation, thus obtaining a set of exact equations that can be solved by standard methods of integration for any impinging light beam. As examples of applications, we consider the particular cases of linearly and circularly polarized Gaussian and Bessel beams inside a KTP crystal. The numerical calculations follow the evolution of the refract…

The fine structure of the vortex-beams in the biaxial and biaxially-induced birefringent media caused by the conical diffraction

We consider the paraxial propagation of nondiffracting singular beams inside natural biaxial and biaxially-induced birefringent media in vicinity of one of the optical axes in terms of eigenmode vortex-beams, whose angular momentum does not change upon propagation. We have predicted a series of new optical effects in the natural biaxial crystals such as the stable propagation of vector singular beams bearing the coupled optical vortices with fractional topological charges, the conversion of the zero-order Bessel beam with a uniformly distributed linear polarization into the radially-, azimutha…

Direct micro-structuring of Si(111) surfaces through nanosecond-laser Bessel beams

We present here a nanosecond laser ablation of Si(111) wafer with diffraction-free (Bessel-$J_0$) beams. First, the Axicon a conical shaped optical element for beam shaping is characterized with a visible and infrared light sources. Then, ablation profiles are obtained with Bessel beams generated for $α=1^{\circ}$ and $α=20^{\circ}$ base angles, then they are characterized via a Scanning Electron, an Atomic Force and an Optical Interferometric Microscopes. Experimental results compared with theoretical predictions obtained by using Bessel functions. Results show that Bessel beams give possibil…

Wavefronts, light rays and caustic associated with the refraction of a plane wave by a conospherical lens

The aim of the present work is to introduce a lens whose faces are a conical surface and a spherical surface. We illuminate this lens by a plane wavefront and its associated refracted wavefronts, light rays and caustic are computed. We find that the caustic has two branches. The first is constituted by two segments of a line, one part of this caustic is real and the other one virtual. The second branch of the caustic is a two-dimensional surface with a singularity of the cusp ridge type. It is important to remark that the two branches of the caustic are disconnected. Because of this property w…