Krischek, R., Wieczorek, W., Ozawa, A., Kiesel, N., Michelberger, P., Udem, T., & Weinfurter, H. (2010). Ultraviolet enhancement cavity for ultrafast nonlinear optics and high-rate multiphoton entanglement experiments. Nature Photonics, 4(3), 170-173. doi:10.1038/NPHOTON.2009.286.