Polarization-sensitive terahertz reflective multi-channel beam separation by cascaded configuration

Abstract

In this paper, we proposed polarization-dependent terahertz reflective beam splitters under normal incidence, in which resonance-domain diffraction gratings with period comparable to incident wavelength are adopted to achieve multi-channel beam separation, appropriate total diffraction efficiency, and good efficiency uniformity. At the frequency of 2.5200 THz (correspondingly the wavelength λ = 118.83 μm), the beam splitters can implement energy output varying from dual- to seven-port. For transverse electric (TE) polarization, the total efficiency of the beam splitters can reach ~ 95% (assuming the values 96.04%, 96.84%, 94.71%, 96.32%, 96.47%, and 95.08%, respectively, when the splitter’s output ports change from two to seven). For transverse magnetic (TM) polarization, under different structural parameters (namely the heights of the grating ridges h1 and h2) from TE polarization, the corresponding values are 96.62%, 95.23%, 92.81%, 93.11%, 92.99%, and 93.19%, respectively. Our results (Table 2) demonstrate that all splitters, irrespective of the number of output ports, can provide appropriate total diffraction efficiency and good uniformity. Through rigorous coupled-wave analysis (RCWA), we derived the fabrication tolerance of the incident wavelength and period, which highlights the reliability of the proposed terahertz beam splitters.