Mach–Zehnder Interferometer for Real-Time In Situ Monitoring of Refractive Microlens Characteristics at the Fabrication Level

We present a Mach-Zehnder interferometer to monitor in situ and in real-time the geometrical and optical characteristics of refractive microlenses during their fabrication process to increase the fabrication accuracy as well as the sample-to-sample reproducibility. We demonstrate for one test case that the deviation of our developed interferometric system against commercial instrumentation is smaller than 5 % while its repeatability error is smaller than 1.5% after calibration against dedicated off-line instrumentation. To conclude, we demonstrate the practical usefulness of this interferometer by applying it to the fabrication of microlenses by deep proton writing.