High-efficiency two-port beam splitter of total internal reflection fused-silica grating

Abstract

We describe high-efficiency two-port beam splitters of total internal reflection (TIR) gratings, where incident waves are reflected in the 0th and −1st orders with the same energy, respectively. To achieve high efficiency and uniformity between two orders, the grating duty cycle and depth are optimized using rigorous coupled wave analysis for a laser wavelength of 800 nm. With the optimized grating profiles, the TIR grating can work as a 50/50 beam splitter for not only TE or TM polarization but also both TE and TM polarization. Efficiencies can reach nearly 50% × 2 = 100% in the 0th and −1st reflected orders. It indicates that high efficiency can be obtained based on a TIR grating instead of complicated structures. For high efficiency of a TIR grating and a high damage threshold of fused silica, the presented two-port beam splitter gratings should be useful elements in numerous practical applications, especially in high laser power systems.