I checked the Mephisto 2000NE (SN 1228, 2002/08 bought by ICRR, Photo 1) that was used for ISS in Toyama University.
[Background]
Because of the air conditioner trouble in this summer in the clean room at Toyama University, the output power of this laser was reported to reduce at the level fo 0.9W (2A) from 1.6W.
[Check]
1) FIrstly, I found a very dirty spot on the output AR window surface (no photo, sorry). Although I could not judge wheather this dirty spot was on the outside or inside of the AR window, anyway, I wiped it by a cotton bar with clean water (not pure water). Then, it can be completely removed at the level of eye balls judge.
2) I set up a power measuremnt setup as photo 2/3 in the clean room beside the draft chamber room in the KAGRA site. The used power meter is coherent Model 150-50, that can detect from 300mW to 150W. The expected 2W power is within this range.
3) The measured power was 1.75W at 2.0A as Photo 4/5. Photo 6/7 shows the wave length setting (1064nm), and mW level background without IR lasser input.
4) According to our (Miyoki, Uchiyama) memory, the max current was 2.1A for Mephisto 2000NE around 2004. Also, I found the record to use 2.3A in 2002 May to check other Mehisto 2000NE power. Anyway. 2.0A and 1.75W output might be enough for ISS experiment.
[Temporal conclusion and next step]
The main power reduction reason was the dirty spot on the AR window. I don't know wheather we can improve more when we will wipe the crystal or not.
Please check by using other power meter again to confirm the laser power, as the next step.