Highly Efficient All-dielectric Metasurfaces for Airy Beam Generation in Visible Domain

Metasurfaces, the planar analog of bulk metamaterials, can be patterned at the interface of two media to control the amplitude, polarization, and phase of the incident light. Metasurfaces have provided a unique platform for the on-chip realization of various interesting phenomena such as light-twisting, structuring, lensing, imaging, beam-splitting, etc. Since the performance of metasurfaces based on metallic scatterers is restricted by ohmic losses and associated optical absorption, lossless dielectric materials (in the spectrum of interest) provide a promising alternative to acquire higher transmission efficiency. In this article, we utilize hydrogenated amorphous silicon (a-Si: H) nano-scatterers (with a subwavelength thickness of 300 nm), which provides a cost-effective (compared to TiO₂ and GaN) and low-loss (compared to metallic counterparts) alternative, to design an efficient metasurface in the visible domain. The proposed metasurface can generate the finite energy Airy beam by simultaneously engineering the cross-polarized transmission amplitude and phase of the transmitted electromagnetic wave at the visible wavelength of 633 nm. The polarization and phase are engineered by varying the orientation of nano-bars while cross-polarized transmission amplitude is optimized by tuning the geometric parameters of nano-bars. Higher cross-polarized transmission amplitude (73%) is achieved compared to previously reported work. The proposed design will help us in developing subwavelength-thick flat devices that have numerous applications in integrated optics such as optical manipulation, bio-sensing, beam shaping, and forming optical bullets.