Concern on mirror optical losses by H.Yamamoto
Scattering loss of 45ppm by low-freq (>1mm) surface error of 1nm RMS (25ppm with 0.75nm RMS).
Scattering loss of 6ppm by high-freq (<1mm) surface error of 0.2nm RMS.
- Unexplainable point scattering loss of 10ppm (realistic estimate would be 15-30ppm).
These alone would make the total scattering loss already 61ppm (with 1nm LF RMS) or 41ppm (with 0.75nm LF RMS).
- Besides, absorption at the coatings, 0.5ppm based on the LMA coating on Silica substrate, can easily go worse by several ppm by contamination.
LF RMS could be improved if we spend enough money and time. LIGO set the requirement to be RMS<0.5nm and Tinsley has achieved that value.