Development of High Power Continuous Wave Lasers, Components, and Optical Contamination Diagnostics for Future Ground-based Gravitational Wave Detectors

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This research award will enable the continuation of investigations important to the Advanced Laser Interferometer Gravitational-wave Observatory (Advanced LIGO). First, the quality of the mirror surfaces is crucial to the performance of Advanced LIGO. A method is under development to monitor mirror surface contaminants during the operation of Advanced LIGO using a nonlinear optical technique known as surface second harmonic generation (SSHG). Theoretical investigation of SSHG generation from multi-layer dielectric coatings and experimental investigation of SSHG, specifically investigations of controlled contamination on superpolished mirrors used in Advanced LIGO, will be conducted. Second, optical isolation of high power laser beams is important for Advanced LIGO, and this research addresses issues with the development of optical (Faraday) isolators capable of handling higher laser powers. Activities to be undertaken are characterization of thermal depolarization, isolation ratio, and thermal lensing for a large aperture Faraday isolator design and testing of Advanced LIGO Faraday isolators in vacuum.

Advanced LIGO will open a new astronomical window --- the ability to probe some of the most cataclysmic events in universe through the emission of gravitational waves, a mechanism proposed by Albert Einstein almost 100 years ago, but yet to be directly observed. These investigations will both aid in the operation of Advanced LIGO over long time scales and potentially improve its performance once it is in operation. They will also impact many applications which use high power lasers. Finally, this research will also foster international collaborations.