Triple-channel reflective splitter in terahertz band by second-order Littrow illumination

In this paper, a triple-channel reflective beam splitter in terahertz band with connecting layer under second Bragg incidence is presented. A rigorous coupled-wave analysis is applied to optimize the profile of the grating at 2.52 THz. The optimal parameters of the grating are also verified by using the finite element method to ensure the accuracy of the data. The impact of the incident angle, incident wavelength, duty cycle, and period is analyzed in detail. For the optimized grating working in terahertz band, results for diffraction efficiencies approaching over 30% for transverse-electric polarization in three propagating orders and for transverse-magnetic polarization in the -1st order and -2nd order are derived. Obtaining stable and superior performances, the proposed three-port beam splitter working in the terahertz band is novel and could be an inspiration to design new gratings.