Development of Multi-Layer Anti-Reflection Structures for Millimeter-Wave Silicon Optics Using Deep Reactive Ion Etching Process

To show the technical feasibility of high-frequency and broadband anti-reflection (AR) coating for silicon optics in millimeter wavelengths, we fabricated a prototype of the four-layer sub-wavelength structure (SWS) using a combination of deep reactive ion etching (DRIE) and dicing processes. We also fabricated a three-layer SWS using a multi-layer DRIE technique. The described processes allow to obtain physical prototypes that are close enough to those designed that their simulated reflectances are slightly worse than expected. The simulations of the obtained three- and four-layer prototype showed the averaged reflectances of 5.2 % at 150-450 GHz and 3.7 % at 100-450 GHz, while the designed SWSs showed 1.6 % and 2.0 %, respectively.