Ultrawide-Angle Optical Elements With Enhanced Transmittance Obtained by a Half-Etched Moth-Eye Structure Coating on Infrared Substrates

Abstract

With the traditional multilayers coating, it is difficult to achieve broadband and wide-angle antireflection optical properties simultaneously. As one of the most promising candidates for omnidirectional and broadband antireflection coating, the moth-eye structure has gained considerable attention in the past several decades because of its excellent optical performance and self-cleaning function. The challenges in the use of this technology, namely, its manufacturing cost and mechanical structural stability, limit its popularization. In this paper, a moth-eye structure surface combined with a residual layer of an identical material is proposed; the proposed composite structure can be formed by a one-step process of half-etched technology. For the design and optimization of the composite moth-eye structure, composite structures were compared by performing effective medium approximation (EMA) and rigorous coupled– wave analysis (RCWA). The structural parameters of the micro–nano surface were optimized to increase the mechanical stability considerably. The results showed that the optimized composite moth-eye structure has high transmittance for incident angles from 0° to 80° in the infrared spectrum. Furthermore, the transmission diffraction at high orders was suppressed efficiently at super-wide incident angles.

Keywords

• Subwavelength structures
• nanostructures
• antireflection coatings
• effective medium approximation
• rigorous coupled-wave analysis