We study the fine structure of transverse modes of an optical micro cavity. We measure the transmission of a 633 nm He-Ne laser as a function of the cavity length, from which we can extract the...Show moreWe study the fine structure of transverse modes of an optical micro cavity. We measure the transmission of a 633 nm He-Ne laser as a function of the cavity length, from which we can extract the mirror radius of curvature, the well known paraxial shifts, and higher-order corrections. The goal is to distinguish between fine structure caused by non-paraxial effects and mirror related effects. We find that the resonant cavity lengths predicted by the non-paraxial model is only correct for certain resonant modes. We also measure the mirrors with an AFM and find that mirror related effects are small compared to the non-paraxial effects. Further investigation with a polarization-resolving CCD camera reveals that the polarization profiles of transverse modes are similar to what the non-paraxial theory predicts, but it also shows that the occurrence of almost all modes is shifted. The experiment suggests that the models are good, but insufficient to fully describe the fine structure of a Fabry-Pérot interferometer.Show less
