Twisted Non-Diffracting Beams through All Dielectric Meta-Axicon
We demonstrate transmission-based all-dielectric, highly efficient (≈ 73.4%) and polarization-insensitive meta-axicons (for the visible wavelength of 633 nm) to generate zero and higher order Bessel beams without using additional components. The Bessel beams, owing to their diverse applications and non-diffractive properties, harbor great interest for the scientific community. It is shown that propagation length can be elongated through a lower numerical aperture (~ 2600 λ for NA = 0.1) whereas higher full width at half maximum (< 0.5 λ) can be obtained for a higher numerical aperture (for NA ≥ 0.7). Our dielectric material, hydrogenated amorphous silicon (a-Si:H) provides a significant efficiency advantage over plasmonic and other high-indexed all-dielectric (e.g., TiO2 and GaN) metasurfaces in terms of cost, ease-of-fabrication, and CMOS compatibility. The finite difference time domain (FDTD) technique based numerically simulated and experimental results show excellent agreement. Due to technological and scientific importance of the Bessel beams, the recommended material and meta-axicons provide an efficient and compact platform for realizing various advanced applications like optical manipulation, optical alignment, laser fabrication, imaging, and laser machining.