Subwavelength Diffractive Optical Elements for Generation of Terahertz Coherent Beams with Pre-Given Polarization State

Abstract

Coherent terahertz beams with radial polarization of the 1st, 2nd, and 3rd orders have been generated with the use of silicon subwavelength diffractive optical elements (DOEs). Silicon elements were fabricated by a technology similar to the technology used before for the fabrication of DOEs forming laser terahertz beams with pre-given mode content. The beam of the terahertz Novosibirsk Free Electron Laser was used as the illuminating beam. The experimental results are in good agreement with the results of the computer simulation.

A Review on Reconfigurable Metalenses Revolutionizing Flat Optics

“…Within the diffractive optics community, [67][68][69] there's a contention that producing a multilevel diffractive lens [70] characterized by a surface profile comprising several discrete surface heights-presents a more straightforward task compared to crafting a binary ML, which consists of only two-level surface heights. [71] This argument hinges on the notion that the feature size of the diffractive lens is generally larger.…”

“…[176] This is especially important for damage-resistant applications using high-power laser sources. [67] ii. Material selection: Evaluate which materials are suitable for the intended purpose.…”

“…[ 176 ] This is especially important for damage‐resistant applications using high‐power laser sources. [ 67 ] Material selection: Evaluate which materials are suitable for the intended purpose. The choice of materials will significantly influence the MS's properties. Determine feature size: These parameters—spectral range and material selection—ultimately dictate the required feature size of the MS. For applications where longer wavelengths are acceptable and lower refractive indices are permissible, methods such as two‐photon polymerization and nano‐imprint lithography offer attractive options.…”

Combined high-power terahertz vortex Bessel beams: formation and identification

“…In such cases, diffractive optical elements (DOEs) are a suitable technique. Previous works by our team have demonstrated the fabrication and application of various DOEs for controlling the transverse-mode composition and polarization state of high-power THz generation at the Novosibirsk Free Electron Laser (NovoFEL) 11,12 , as well as for the formation of Bessel beams with OAM 13 . The use of mode multiplexing requires solving the inverse problem of demultiplexing.…”

Refractive multi-conical elements for cylindrical vector beam generation

“…There are various approaches to the formation of inhomogeneously polarized beams,including interference methods [45][46][47][48] , diffractive optical elements [49][50][51][52][53] , spatiallight modulators [54][55][56][57][58][59][60][61] , subwavelength gratings and metasurfaces [62][63][64][65][66][67][68][69][70] , aswell as anisotropic plates and crystals [71][72][73][74][75][76][77][78][79] . All methods have their advantages and disadvantages.SLMs convert only part of the transmitted light, thereby reducing the polarization extinctionratio.…”