Silicon-based metasurfaces for vortex beam generation

Silicon metasurfaces were fabricated on fused silica substrates by using sputtering, electron beam lithography and reactive ion etching. A chromium etch mask was used to protect the silicon during plasma etching. We designed a hologram with phase range of 0 - 1.17π to generate a higher order Bessel beam. The device produced the expected beam profile and the presence of charge 3 was confirmed using a interference test. Tests on spiral plate devices were less successful owing to the thickness non-uniformity in the sputtered Si film.