Beghuin, DidierDidierBeghuinBigeon, JohnJohnBigeonLopera-Acosta, MariaMariaLopera-AcostaSamsom, HansHansSamsomDuflos, FredericFredericDuflosPeeters, WoutWoutPeetersHumblet, AlexisAlexisHumblet2026-07-272026-07-2720261559-128X2155-3165https://imec-publications.be/handle/20.500.12860/60005<jats:p> Silicon MEMS micromirrors face critical thermal challenges from high optical loads, requiring accurate temperature validation for reliable design. Finite element thermal models are hindered by parameter uncertainties, while standard non-contact measurement methods fail for thin silicon structures. We present a novel optical technique, to our knowledge, using coherence-tuned Fabry–Perot interferometry to accurately measure the micromirror plate temperature. By employing two sequential interferometers with an incoherent source, we selectively isolate the temperature-dependent refractive index change in the mirror plate, excluding parasitic reflections from the underlying substrate. The method achieves temperature uncertainty on the order of ±2 <jats:sup>∘</jats:sup> C across the 40°C–200°C range when calibrated against a thermistor. This approach enables thermal characterization of MEMS devices where conventional contact-based methods are impractical. </jats:p>engJournal article10.1364/ao.590792WOS:001755821300024SILICONMEDLINE:420292682155-3165