Theoretical giant circular dichroism and broadband asymmetric absorption enabled by multilayered chiral metastructure-photonic crystals in the near-infrared regime

Abstract

In this paper, a type of multilayered chiral metastructure-photonic crystal (MCMPC) is proposed to investigate the absorption properties of circularly polarized waves in the near-infrared regime. The MCMPC consists of three metastructure-photonic crystal (MPC) units separated by two air spacers, including metallic silver, tungsten, air, silicon dioxide and an isotropic dielectric material. The absorption of right-handed circularly polarized (RCP) waves reaches nearly 0.96 in forward propagation, whereas left-handed circularly polarized (LCP) waves maintain absorption below 0.3 under identical incidence. Therefore, the configuration demonstrates strong circular dichroism (CD) with a peak value of 0.78 at 332 terahertz (THz), resulting in distinct polarization-selective absorption responses. The results were interpreted through electric field energy density distributions to elucidate the working mechanisms. Remarkably, the chiral multilayer configuration enables a relative bandwidth of 16.2% for forward RCP wave absorption above 0.9 while suppressing backward absorption below 0.19. The operating bandwidth spans 312–367 THz, achieving a peak value of the asymmetric absorption coefficient (difference between forward and backward RCP wave absorption) of 0.79 at 327 THz. In addition, the influences of the inclination angle and vertical height of the layers in the MPC units, along with external variables such as the incident angle and polarization angle, are investigated in detail. Thus, the proposed MCMPC resolves the fundamental challenge of the concurrent realization of intense CD, broadband functionality, and asymmetric absorption in chiral systems, which holds important potential for advanced polarization-selective devices in integrated photonic platforms.