Collinear acousto-optical filtration of polychromatic Bessel light beams in lithium niobate crystals

The features of collinear acousto - optical filtration of quasi - diffractive Bessel light beams of o- and e-type in uniaxial crystals are investigated. Using the method of overlap integrals, an expression is found for the diffraction efficiency depending on the parameters of the acousto-optical interaction, as well as on the values of the overlap integrals. It is shown that for the zero-order mode of a Bessel light beam for a lithium niobate crystal under conditions of transverse phase synchronism and in the optical spectrum range of 0.4-0.7 μm, the filter bandwidth of ∼0.2 nm is achievable; with an increase in the order of the mode m≥1, the increase in the bandwidth is insignificant and is ∼0.23 -0.24 nm.

Transformation of Evanescent Bessel Light Beams into Propagating Quasi-Nondiffracting Beams in Epsilon-Near-Zero Hyperbolic Metamaterials

In this paper, we show the possibility of rebuilding of the structure of wave vector surface and the appearance of its local parts with near zero curvature for epsilon-near-zero hyperbolic metamaterials. It is established that when evanescent Bessel light beam falls in special directions related to these local parts, it is transformed into propagating one. The features of transformed beam are analyzed.