Automated integration of time-control in a pseudo-polychromatic monitoring strategy for complex thin-film filters

Precise optical monitoring of the layer thickness is crucial for the fabrication of complex error-sensitive thin-film filters. In this study, we extend a previously developed pseudo-polychromatic monitoring algorithm by integrating automatically placed time-controlled layers. While time-based monitoring is often applied empirically for convenience, we highlight its positive impact on the performance of the pseudo-polychromatic approach. Concerning automated selection of time-control, several configurations were tested on three multi-bandpass filter designs. Results show that hybrid strategies can reduce equivalent random thickness errors by more than 0.1-0.2 nm, compared to purely optical approaches. Although results are specific to our monitoring scheme, this work opens the door for broader analytical studies on the influence of time-controlled layers across a range of commonly used optical monitoring techniques.