Plasmonically enhanced composite vortex beam generation using ultra-thin dielectric fork gratings

• DOI: 10.1364/josab.460366
• Publication Date: 2022-06-28T12:00:46Z
• Authors: Nirjhar Kumar; Ankit Arora; Ananth Krishnan
• Keywords: Fork (system call)

We experimentally demonstrate a simple method for the generation of composite vortex beams using resonant ultra-thin dielectric fork gratings (UFGs) thicknesses an order magnitude less than incident wavelength. The degradation in diffraction efficiency these at reduced was computationally shown to be compensated by introducing thin continuous gold layer (Au, 30 nm) between grating and substrate. At resonance wavelength, UFGs with Au <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>∼</mml:mo> </mml:mrow> <mml:mn>4</mml:mn> </mml:math> times higher when compared that without Au, which attributed plasmon-induced transmission enhancement. were fabricated optimized geometric parameters electron beam lithography. These showed lattice-plasmon wavelength corresponding vector, resulting specific polarization selectivity. Further, hybrid designed replacing central concentric circular region UFG another different topological charge. resulted formation beams, indicating relative spatial phase imparted lattice plasmon preserved leaked radiation. results can help designing integrated, ultra-thin, low aspect ratio optical-phase-singularity structures enhanced optical sources, detectors, sensing applications.