R&D (FilterCavity)
MarcEisenmann - 19:26, Wednesday 06 December 2023 (3366)
SHG recovered

power before shg a bit higher than usual ~840mW

installed power meter in transmission of SHG

tuned to recover fundamental mode

actually the lens installed on rail just before SHG was not fixed. I tried to tune it a bit but it seemed that the initial position was quite good (48mm).

it was a bit hard to tune as when it is unscrewed it is also tilted. If needed, could spend time to have a finer tuning.

installed power meter in reflection of SHG (in reflection of 1st dichroic before beam dump)

further tuned alignment

tuned SHG modulation phase to 70deg (from 0deg) to recover the usual shape.

can see weak green in reflection and error signal seems half of usual ~1VpK

found out that temperature control of SHG and OPO was not turned on (actual temp was around 11kOhm)

after thermalisation recovered error signal ~2.4Vpk and could lock SHG.

Green power before EOM is ~247mW (also a bit larger than usual due to higher input laser power)

 

A bit strange thing is the GRMC refl pd has a quite strong noise at 100 Hz. It disappears when ceiling light is off though.