Flat top beam profile cavity prototype

Mirror thermal noise is one of the fundamental factors limiting the sensitivity of gravitational wave interferometric detectors. Classical Gaussian beams "interrogate" only a small fraction of the mirror surface, and therefore are not well suited to average out fluctuations and minimize the thermal noise. It has been calculated that Mat beam profiles would be better suited to average over thermal fluctuations and would allow sensitivity improvements that would more than double the "reach" of GW interferometric detectors. Non-spherical mirrors, shaped to support flat beam profile beams, have been designed and fabricated. A dedicated interferometer has been built to test the performance of these mirrors. We report on the status of this development.