Generation Of Nondiffracting Beams Research Articles

Subwavelength generation of nondiffracting structured light beams

Nondiffracting light beams have been attracting considerable attention for their various applications in both classical and quantum optics. Whereas substantial investigations on generation of the nondiffracting beams were made, their lateral dimension is much larger than optical wavelength. Here we present both theoretically and experimentally a study of the generation of nondiffracting light beams at deep-subwavelength scale. The highly localized light field is a result of in-phase interference of high-spatial-frequency waves generated by optical sharp-edge diffraction with a circular thin film. It is shown that the generated beam can maintain its spot size below the optical diffraction limit for a distance of up to considerable Rayleigh range. Moreover, the topological structure of both the phase and polarization of a light beam is found to be preserved when it passes through the diffractive configuration, which enables generating nondiffracting vortex beams as well as transversely polarized vector beams at deep-subwavelength scale. This work opens a new avenue to manipulate higher-order vector vortex beams at subwavelength scale and may find intriguing applications in subwavelength optics, e.g., in superresolution imaging and nanoparticle manipulation.

Nondiffracting beam emission from hyperbolic metasurfaces

We demonstrate highly directive and transversely confined emissions from hyperbolic metasurfaces (HMSs) to free-space. The generation of such beams is attributed to the narrow hyperbolic isofrequency contour, such that only propagating waves with their wavevectors near normal incidence can transmit through the medium. The directions of transmitted waves’ Poynting vectors are altered by the medium and become parallel to the propagation direction, resulting in the generation of nondiffracting beams. We also suggest a realization of the proposed HMS using a layered silver-dielectric structure for optical wavelengths.

Generation of nondiffracting beams through an opaque disk

A new method of generating nondiffracting beams is presented. It consists of focusing a Gaussian beam in the vicinity of an opaque disk. A beam is generated whose central peak is surrounded by a wide number of bright rings (approximately 250). After collimation, the beam propagates without changing the rings' radii, similar to a diffraction-free beam. The central peak can conserve its dimension over more than 5 m. The diameter of the central peak is adjusted by choosing the focal length of the collimating lens. Experimental results are well predicted by our theoretical developments that simulate exactly the paraxial diffraction.

The generation of nondiffracting beams using inexpensive computer-generated holograms

We present a simple experimental procedure for producing a computer-generated hologram of good quality. As an example, the transverse intensity and phase structure of nondiffracting beams is investigated.

Generation of nondiffracting beams by spiral fields.

In this paper we demonstrate that spiral fields generate nondiffracting dark beams. A collimated laser beam incident on a compact disc, i.e., a commercial CD, was used as mask for the generation of spiral fields. We study theoretically and experimentally the intensity distribution near the axis of the optical system.

Generation of nondiffracting beams by diffractive phase elements

We present a design of the diffractive phase elements (DPE’s) that produce nondiffracting beams according to the beam-shaping scheme, in which the incident Gaussian-profile beam is converted into a Bessel-function J0 beam. An optimization method is applied to solving this special beam-shaping problem. Numerical investigation of the generating J0 Bessel beam shows that the designed DPE can satisfactorily produce the J0 Bessel beam.