Broadband polarization-independent reflective 1×2 beam splitters under normal incidence based on encapsulated metal-dielectric gratings

摘要

An encapsulated metal-dielectric grating is proposed for realization of reflective broadband polarization-independent 1×2beam splitter under normal incidence. One can quickly choose a grating structure to realize ultrabroad working wavebandby using unified designing method for low-dispersion materials based on the diffraction efficiency map versus thenormalized period and depth. Moreover, the center wavelength can be flexibly changed. As an example, a reflectiveultrabroadband polarization-independent 1×2 beam splitters operating at wavelength of 1550 nm is designed under normalincidence. The simulation results indicated that a bandwidth of 144 nm could be achieved for the total efficiency over 92%.This kind of broadband polarization-independent 1×2 beam splitters could be found in a variety of applications, such asultrashort pulse splitting, coherent beam combination, complex vector beam shaping, and also high precision displacementmeasurement.