Abstract
Two-dimensional metamaterials, consisting of an array of ultrathin building blocks, offer a versatile and compact platform for tailoring the properties of the electromagnetic waves. Such flat metasurfaces provide a unique solution to circumvent the limitations imposed by their three-dimensional counterparts. Albeit several successful demonstrations of metasurfaces have been presented in the visible, infrared, and terahertz regimes, etc., there is hardly any demonstration for ultraviolet wavelengths due to the unavailability of the appropriate lossless materials. Here, we present diamond as an ultra-low loss material for the near and deep ultraviolet (UV) light and engineer diamond step-index nanowaveguides (DSINs) to achieve full control over the phase and amplitude of the incident wave. A comprehensive analytical solution of step-index nanowaveguides (supported by the numerical study) is provided to describe the underlying mechanism of such controlled wavefront shaping. Due to the ultra-low loss nature of diamond in near and deep UV regimes, our DSINs and metasurfaces designed (from them) exhibit a decent efficiency of ≈ 84% over the entire spectrum of interest. To verify this high efficiency and absolute control over wavefront, we have designed polarization-insensitive meta-holograms through optimized DSINs for operational wavelength λ = 250 nm.
Highlights
Two-dimensional metamaterials, consisting of an array of ultrathin building blocks, offer a versatile and compact platform for tailoring the properties of the electromagnetic waves
Full-wave Finite-Difference Time-Domain (FDTD) simulations are performed for parametric optimization of the unit cell, whereas perfect matching layers (PML) boundary conditions are employed along the z-axis and periodic boundaries are employed along x, y-axis
To fulfill the gap generated by the absence of the appropriate lossless dielectric material for near and deep ultraviolet wavelengths, we proposed diamond material as a best-suited candidate to demonstrate highly efficient phenomena
Summary
Two-dimensional metamaterials, consisting of an array of ultrathin building blocks, offer a versatile and compact platform for tailoring the properties of the electromagnetic waves. Based upon the concept of index waveguide theory or Mie resonances, these all-dielectric metasurfaces appearing as a best-suited candidate for the realization of transmission-type efficient solutions In this regard, lossless dielectric materials like gallium nitride (GaN), titanium dioxide (TiO2), silicon nitride (Si3N4) and hydrogenated amorphous silicon (a-Si:H) present themselves as ideal contestants and successfully employed to realize numerous applications in infrared and visible spectrums[33,34,35,36]. Lossless dielectric materials like gallium nitride (GaN), titanium dioxide (TiO2), silicon nitride (Si3N4) and hydrogenated amorphous silicon (a-Si:H) present themselves as ideal contestants and successfully employed to realize numerous applications in infrared and visible spectrums[33,34,35,36] These dielectric materials offer significant absorption for the near and deep ultraviolet regime, sophisticated fabrication techniques required to implement these metasurfaces have hampered their integration with practical applications. This point can be understood with the help of the following mathematical calculation: Scientific Reports | (2020) 10:18502 |
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