cvd diamond optics with moth-eye antireflective surface structures produced by molding technique

Antireflective surface structures on diamond films were used to the improve optical transmission of diamond components. Two types of surface profiles (arrays of pyramids and randomly arranged columns) were fabricated by growing diamond on patterned Si templates using the microwave plasma CVD technique. Inverted pyramids were produced in silicon by anisotropic wet etching, while random micron-sized vertical pores were formed on electrochemically etched p-Si. After diamond deposition, the substrate was removed to obtain free-standing diamond films with regular pyramids or columns on the substrate (nucleation) side. An increase in infrared transmission up to T=80% was observed for the structured surfaces at wavelengths lambda>10 mu m when the growth side was polished. A further increase in transmission could be achieved by depositing an antireflective coating on the growth side side. The molding technique is reproducible and applicable for the fabrication of large diamond components.