Fabrication of the antireflection structure on aspheric lens surface and lens holder

Abstract

The properties of optical lenses deteriorate due to reflection in the lens surfaces. Therefore, there is an increasing demand for an antireflection structure (ARS). To solve this problem, lens surfaces are designed based on a moth-eye structure, which is a type of ARS. In our previous study, we have successfully fabricated an ARS on a spherical lens such as a convex lens by using the roll-press method, which consists of a liquid transfer imprint lithography (LTIL) process. LTIL is the most effective process for producing a thin residual layer. The most ideal construction of the residual layer is less than a quarter of the wavelength of the incident light. When the incident light is within the wavelength of visible light (400–700nm), the ideal condition is less than 140nm. In this case, a flexible mold was used in the process of fitting the spherical lens with a mold. However, when the substrate is more complex, such as an aspheric lens or an aspheric lens with groove area, the aforementioned roll-press method is not suitable because the mold and the transfer substrate do not fit well together. As the solution, we prepared the reverse type replica lens, the shape of which is reverse of an aspheric lens. This reverse lens was fabricated the ARS, and used the reverse type replica mold to transfer an aspheric lens surface and holder part. Additionally, the reverse type replica mold was fabricated using the flexible replica mold. Further, the flexible replica mold completely fit with the lens groove area, so it was possible to fabricate the ARS on the reverse type replica lens. In this study, the process of fabricating the ARS on the aspheric lens surface and the holder part was investigated. We successfully developed a process of fabricating the ARS with a uniform height of more than 200nm and a thin residual layer of less than 80nm in all parts. Furthermore, this process achieved a low reflectance rate of around 0.2% at the wavelength of visible light. Thus, this process would suitable for fabricating ARS on more complicated substrates, such as double-sided aspheric lenses.