Cavity-based single photon emission possesses a very high potential for future quantum networks and quantum communication systems. Fabry-Perot cavities especially, are a good candidate for these applications, thanks to a circular mode profile emission and low-lasing threshold. These properties are related to the small volume of the active region and the use of highly reflective Distributed Bragg mirrors (DBRs). The reflectance of the DBRs is related to the finesse of the cavity. In order to assure a strong coupling in the cavity, a high finesse is required and therefore a reflectivity value as high as 99.9999%. Achieving such a difficult goal faces many technical challenges and limiting parameters such as optical losses (scatter and absorption) and other limitations related to thin film coating technologies. The control of the mirror fabrication and losses will be addressed in this paper.