Broadband asymmetric light transmission based on all-dielectric metasurfaces in the visible spectrum

An asymmetric transmission device composed of all dielectric phase gradient metasurfaces on the dielectric substrate in the visible wavelengths is proposed and designed. In order to verify its operation principle and investigate its asymmetric transmission performance, ray and wave analyses are employed together. Specifically, ray tracing and finite-difference time-domain techniques are carried out in the study. The analytical calculations of the designed structure are confirmed with the results of the ray and wave analysis. It is also demonstrated that broadband and high contrast asymmetric transmission occur across nearly the entire visible spectrum from wavelengths of 500-715 nm. Especially, the difference of transmission between forward and backward illuminations in the design wavelength of 532 nm is found to be nearly 90% under TM polarization. In addition, it is indicated that a slight degradation in the asymmetric transmission performance of the structure occurs due to the change of the light polarization. It is shown that the asymmetric transmission has been directly related to the total reflection of the light for only one direction excitation case. The proposed structure can be fabricated with emerging nanofabrication techniques in conformal metasurfaces and can be realized in different wavelength ranges.