Estimation Method for Surface and Medium Loss of Fabry-Pérot Etalon

The Fabry-Pérot (FP) etalon is widely applied in experimental research across various fields. In most experiments, the etalon is generally regarded as an ideal optical device. However, if there is any loss in the FP etalon, its parameters including transmittance, linewidth, and finesse will be affected, which will in turn affect the experimental results. In this letter, we propose an estimation method for surface and medium losses of FP etalon. When the FP etalon is not filled with any medium, we establish a relationship between the peak transmittance of the etalon and the surface loss through theoretical calculations. When the FP etalon is filled with a medium, we derive a relationship between the peak transmittance of the etalon and both the surface and the medium loss through calculations. The two functional relationships we established provide a theoretical foundation for experimental measurements of the surface and medium loss of the FP etalon. Based on these functional relationships, we propose a method for estimating the surface and medium losses of FP etalon. Our loss estimation method is also applicable to the FP interferometer.