Deterministic design of binary phase-only blazed grating with subwavelength features under limitation on spatial resolution of fabrication technique

We propose a deterministic design method of a blazed grating consisting of a binary grating with subwavelength structures for a multilevel phase modulation. The feasible shapes of binary subwavelength microstructures are restricted to a few kinds of surface profiles by constraints in an actual fabrication technique. The relationship between the feasible shapes of binary subwavelength microstructures and their phase modulations can be calculated by an electromagnetic analysis and tabulated. Using the relationship, a deterministic design of a binary grating with subwavelength structures is simply realized. We have designed the binary blazed grating with subwavelength structures and investigated its performance. Its diffraction efficiency is in good agreement with that by a conventional statistical design method.