A monolithic micro-optical interferometer deep etched into fused silica

For free-space micro-optical systems, the alignment of the components is still a challenging task in manufacturing. Alternatively, a monolithic integration can overcome this problem, but especially for in-plane optical elements in the visible wavelength range, the optical surfaces have to fulfill critical demands. Here, we show a fabrication process that allows the deep-reactive ion etching (RIE) of fused silica-with high optical quality. We achieve vertical sidewalls with etch depths of about 100 mu m with an arithmetic mean roughness of about 72 nm. By using this process, a new in-plane monolithic, free-space interferometer is demonstrated that reaches a resolution of 20 nm with our current setup. (C) 2017 Elsevier B.V. All rights reserved.