Laser-induced molecular contamination de-risking activity for the Laser Interferometer Space Antenna

The Laser Interferometer Space Antenna (LISA) will be the first space-based gravitational wave observatory. LISA uses continuous-wave, infrared laser beams propagating among three widely separated spacecrafts to measure their distances with picometer accuracy via time-delay interferometry. These measurements put very high demands on the laser wavefront and are thus very sensitive to any deposits on laser optics that could be induced by laser-induced molecular contamination (LIMC). In this work, we describe the results of an extensive experimental test campaign assessing LIMC related risks for LISA. We find that the LIMC concern for LISA, even considering the high demands on the laser wavefront, may be greatly reduced compared to that observed at shorter wavelengths or with pulsed laser radiation. This result is very promising for LISA as well as for other space missions using continuous-wave, infrared laser radiation, e.g., in free space laser communication or quantum key distribution.