Asymmetric light transmission based on a 1D triangular metal grating

Abstract

Here, we present a 1D isosceles triangle silver grating on the dielectric substrate. The grating performs asymmetric light transmission (ALT) characteristics for the light with both transverse magnetic (TM) and transverse electric (TE) polarization states over a waveband in the vicinity of 1.55 µm. By checking the efficiency of each diffraction order and the distribution of the electromagnetic field, we found that the ALT characteristics originate from the high transmitted or reflected diffraction channels excited by forward and backward direction incidence. The grating shows the ALT characteristics in a waveband where incident wavelengths are less and more than the period, so that the grating may be a candidate for the wideband ALT devices. It is worth stressing that the contrast ratio (CR) at a specific wavelength can exceed more than 29 dB (the incident angle is 5.6897°; the incident wavelength is 1.7759 µm) under oblique incidence.