Hollow Gaussian beam generation through nonlinear interaction of photons with orbital-angular-momemtum

Orbital Angular Momentum preserving guided mode in helically twisted hollow core photonic crystal fiber at Dirac point

We report trapping and propagation of photonic Dirac mode in a helically twisted hollow core photonic crystal fiber (HC-PCF) where the trapped light in the hollow (air) defect can preserve the orbital angular momentum (OAM). We show that a photonic Dirac point can emerge even in a twisted system for a suitable choice of curvilinear coordinate and the related waveguide defect modes defined in the new basis can preserve the associated OAM during axial translation. The effect of twist rate, defect geometry and crystal dimension on the propagation of OAM carrying trapped Dirac modes is critically …

反向设计非厄密特空心纳米线腔体用于生成光学轨道角动量

Inverse-Designed Non-Hermitian Hollow Nanowire Cavity for Generating Optical Orbital Angular Momentum

本文提出一种反向设计的非厄密特空心纳米线腔体，通过打破横截面镜像对称性生成轨道角动量光，实现了高纯度和高Q因子的腔体模式。

Hollow chain-like beams

To generate hollow chain-like beams the diffraction of the first order Bessel beam by zone plate with two odd open Fresnel zone has been investigated. It has been shown that the capsules size is influenced by the number of the second odd open Fresnel zone and by the zone plate focal length. A hollow chain-like beam has been experimentally generated as a result of the first order Bessel beam diffraction by zone plate with the first and the ninth open Fresnel zones. The orbital angular momentum presence has been proved experimentally. The main features of the beam have been investigated. Suffici…

Terahertz orbital angular momentum modes with flexible twisted hollow core antiresonant fiber

THz radiation is more and more commonplace in research laboratories as well as in everyday life, with applications ranging from body scanners at airport security to short range wireless communications. In the optical domain, waveguides and other devices to manipulate radiation are well established. This is not yet the case in the THz regime because of the strong interaction of THz radiation with matter, leading to absorption, and the millimeter size of the wavelength and therefore of the required waveguides. We propose the use of a new material, polyurethane, for waveguides that allows high fl…

Optimized coupling of cold atoms into a fiber using a blue-detuned hollow-beam funnel

We theoretically investigate the process of coupling cold atoms into the core of a hollow-core photonic-crystal optical fiber using a blue-detuned Laguerre-Gaussian beam. In contrast to the use of a red-detuned Gaussian beam to couple the atoms, the blue-detuned hollow-beam can confine cold atoms to the darkest regions of the beam thereby minimizing shifts in the internal states and making the guide highly robust to heating effects. This single optical beam is used as both a funnel and guide to maximize the number of atoms into the fiber. In the proposed experiment, Rb atoms are loaded into a …

Achromatic orbital angular momentum generator

We describe a novel approach for generating light beams that carry orbital angular momentum (OAM) by means of total internal reflection in an isotropic medium. A continuous space-varying cylindrically symmetric reflector, in the form of \textit{two glued hollow axicons}, is used to introduce a nonuniform rotation of polarisation into a linearly polarised input beam. This device acts as a full spin-to-orbital angular momentum convertor. It functions by switching the helicity of the incoming beam's polarisation, and by conservation of total angular momentum thereby generates a well-defined value…