Transverse-mode coupling effects in scanning cavity microscopy

Julia Benedikter, Thea Moosmayer, Matthias Mader, Thomas Hümmer, David Hunger
2019 New Journal of Physics  
Tunable open-access Fabry-Pérot microcavities enable the combination of cavity enhancement with high resolution imaging. To assess the limits of this technique originating from background variations, we perform high-finesse scanning cavity microscopy of pristine planar mirrors. We observe spatially localized features of strong cavity transmission reduction for certain cavity mode orders, and periodic background patterns with high spatial frequency. We show in detailed measurements that the
more » ... ized structures originate from resonant transverse-mode coupling and arise from the topography of the planar mirror surface, in particular its local curvature and gradient. We further examine the background patterns and find that they derive from non-resonant mode coupling, and we attribute it to the micro roughness of the mirror. Our measurements and analysis elucidate the impact of imperfect mirrors and reveal the influence of their microscopic topography. This is crucial for the interpretation of scanning cavity images, and could provide relevant insight for precision applications such as gravitational wave detectors, laser gyroscopes, and reference cavities.
doi:10.1088/1367-2630/ab49b4 fatcat:4ufaxkrno5bhbiogofxumqwohq