Pulse dispersion, dielectric mirrors and fluorescence yield Summary This case report describes how a two-photon microscope was found to come with a fluorescence yield that was lower than expected; how the underlying cause was found out in a systematic manner; and how the problem was solved. All approaches and solutions are specific for the microscope under question. However, I hope that this report (1) will inspire other people who are troubleshooting or optimizing their microscopes, (2) will help other people better understand two-photon microscopes and the relevance of technical details. Github page The Github web page for this repository can be found online at https://ptrrupprecht.github.io/Photon-yield-and-pulse-dispersion. Context This case report is intended for two-photon microscope users who are keen on understanding more about the technical details and especially about what can go wrong with two-photon microscopes. It is written in a lab journal style and will not be peer-reviewed. Comments, suggestions and corrections, however, are much appreciated. The beautiful publication template for this report had been designed by Andrew York. Contact p.t.r.rupprecht+dispersion(at)gmail.com https://ptrrupprecht.wordpress.com