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

• Multi-channel separation from dual-port to seven-port at the 2.5200 THz frequency. • The efficiency of the 0th order suppressed well for the even-port beam splitter. • Good uniformity and moderate tolerance with optimized multi-channel parameters. 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 h 1 and h 2) 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. [ABSTRACT FROM AUTHOR]