Asymmetric transmission of light waves in a photonic crystal waveguide heterostructure with complete bandgaps.

Here, we theoretically present an on-chip nanophotonic asymmetric transmission device (ATD) based on the photonic crystal (PhC) waveguide structure with complete photonic bandgaps (CPBGs). The ATD comprises two-dimensional silica and germanium PhCs with CPBGs, within which line defects are introduced to create highly efficient waveguides to achieve high forward transmittance. In the meantime, the total internal reflection principle is applied to block the backward incidence, achieving asymmetric transmission. We optimize the design of the PhCs and the waveguide structure by scanning different structure parameters. The optimized ATD shows a high forward transmittance of 0.581 and contrast ratio of 0.989 at the wavelength of 1582 nm for TE mode. The results deepen the understanding and open up the new possibility in designing novel ATDs. The on-chip ATD will find broad applications in optical communications and quantum computing.