Journal: Nanomaterials

Article Title: Highly Efficient Perfect Vortex Beams Generation Based on All-Dielectric Metasurface for Ultraviolet Light

doi: 10.3390/nano12193285

Figure Lengend Snippet: Material properties and parametric optimization of the unit cell. ( a ) Ellipsometry data of the engineered silicon nitride material deposited using plasma-enhanced chemical vapor deposition (PECVD) under different gas ratios of SiH4:N2. Presented dielectric material exhibits negligible absorption loss k = 0.00011 at the ultraviolet wavelengths. ( b ) Schematic illustration of the simulated fundamental building block where the rectangular-shaped nanoantenna of Si 3 N 4 sitting on the sapphire substrate is used for parametric analysis. Finite difference time domain-based FDTD Solution software is used to perform the optimization, where periodic boundary conditions are applied along the x- and y-axes, and PML boundaries are applied along the z -axis. ( c ) The top view of the unit cell consists of a rectangular bar of Si 3 N 4 of the sapphire substrate. Here, U presents the period of the unit cell, L and W indicates the length and width of the nanoantenna, respectively. Numerical optimization of the unit cell reveals the optimized values as U = 280 nm , L = 240 nm , and W = 92 nm . ( d ) The numerically simulated transmission intensity distribution of the diffracted cross-polarized light for wavelength λ d = 300 nm . To obtain the optimized value of the nanoantenna, its length and width are swept in the software. The “+” sign on the ( d ) plot indicates the selected dimensions of the nanoantenna as mentioned above. ( e ) Verification of the nanoantenna to act as a halfwave plate. Nanoantenna is in-plane rotated and the diffracted with the opposite handedness is received and analyzed for complete phase coverage. ( f ) Schematic diagram of the designed UV metasurface with topological charge n = 2 for PV beam generation.

Article Snippet: A schematic description of the simulated unit cell in the Ansys Lumerical Inc. FDTD Solution 2022 R1.4, USA is presented in b, where periodic boundary conditions are used along the x- and y -axis and perfect matching layer (PML) boundaries are applied along the z -axis.

Techniques: Blocking Assay, Software, Transmission Assay