Real-time in situ sag characterization of microlenses fabricated with Deep Lithography with Protons

Abstract

Today different technologies exist that allow the fabrication of individual high-quality micro-optical refractive components and more in particular spherical microlenses. In this paper we will focus on the characterization of the latter components obtained with Deep Lithography with Protons (DLP). In the past we first fabricated the DLP microlenses and secondly a full geometrical and optical characterization was performed. However, this working method is very time consuming due to the amount of experiments needed for a complete calibration of our fabrication process. Therefore, we developed an interferometer for a real-time in situ sag characterization of the microlenses. In a first step we built a Mach-Zehnder interferometer working in the visible wavelength range and demonstrated its proof-of-principle for the determination of the microlens sag. In a next step we then transferred the concept of this interferometer to the closed reactor in which the in-diffusion of monomer vapour in the irradiated zones takes place. This novel approach will allow us to continuously monitor the volume expansion of the desired areas until spherical microlenses with a specific lens sag are obtained.