High-efficiency diffractive beam splitters surface-structured on submicrometer scale using deep-UV interference...

We report highly efficient diffractive beam splitters intended for high-power laser applications. Submicron relief structures that work as an antireflective layer are formed on the surfaces of a splitter to improve its transmitted efficiency. Surface structuring is performed using deep-UV interference lithography and reactive ion etching. As immersed in an index-matching liquid, the resist layer coated on diffractive surfaces is exposed to the interference fringes that are set intersecting the grooves on the surfaces. Rigorously designed structures with a period of 140 nm and a depth of 55 nm are lithographed onto fused-silica splitters. Splitting efficiencies at 266 nm are increased by 8% to compare favorably with a theoretical value, while Fresnel reflections are considerably reduced.