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==Daily Log==
'''11/5/14'''
I'm not sure what happened, but something must have gotten bumped and the 1555 was completely misaligned--no cavity peaks or anything. It was good practice at setting that back up at least. The best way seemed to be to turn the power way down and look at the incident beam and reflected beam with the card and try to overlap them in two places. Then I moved the transmitted photodiode and took off all the filters/covers and put it right at the transmitted side of the cavity. Using the HeNe was helpful for making sure the photodiode was pretty much aligned to where the 1555 beam would come out. Turning the power all the way back up and making small adjustments with the walking mirrors usually got some very small peaks which could them be optimized.
Locking is still inconsistent. It's not too bad under vacuum, but with gas settings that work one day don't work as well another, and the higher the gas pressure the worse it seems to be. I lowered the pressure only about 0.57 V (about 0.07 atm), and was able to achieve pretty good locking--~150 mW transmitted, with the best locks stable for a few minutes. I was able to simultaneously lock with 1064 too (the bandpass filter helped), and I think I can still get sideband generation at this pressure, although the 780 was misaligned and I'm not able to see any 633. Hopefully after fixing that, I'll be able to get some 633 generation and have consistent locking settings and performance at this pressure.
Current successful settings for 1555 lock at 0.07 atm:
course gian: 4 clicks
fine gain: bit over halfway
first integrator: 10 kHz
differentiator: 500 kHz
optical feedback: ~300 mV
'''11/3/14'''
The 1555 lock works pretty well under vacuum when it works. Getting it to work is a problem. It seems to need different settings everyday, so apparently is very sensitive to small fluctuations. When it is working well, I've gotten between 800-1000 mW that is pretty stable in power (often less than 20 mW fluctuations), that can last for over a minute. Again the necessary settings seem to differ everyday, but usually a good lock can be achieved just by adjusting the optical feedback, proportional gain, and auxiliary servo gain. The first integrator is set at 5 kHz, the differentiator is set at at 500 kHz (gain set somewhere in the middle), and the second integrator is off.
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