Reflective diffraction with high efficiency and beam splitter by metal-mirror-based grating

It is interesting and desirable to achieve two functions of high efficiency and two-port output with one reflective grating, which is not easy to acquire by multilayer coatings. We describe the reflective high efficiency element and the two-port beam splitter by the metal-mirror-based grating. By modal method, the design guideline is proposed according to the two-beam interference of the excited modes by incident TE and TM polarizations. Using rigorous coupled-wave analysis (RCWA), accurate grating parameters are optimized by numerical calculation. This indicates that wideband property can be achieved for such a reflective dual-function grating. Furthermore, the element can also be used for beam splitting for TE polarization with the pre-determined angle of incidence. With merits of wideband and so many functions, the reflective elements presented should be useful in a variety of optical systems.