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David Notebook: Difference between revisions
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==Daily Log==
'''7/31/14'''
There's about 150 pW of noise on the lock-in even with all lasers and lights off. This is more than before, since I was able to easily measure a 60 pW signal. I'm not sure what caused the change. Maybe the old photodiode was less noisy and I just haven't looked at such small scales on the new one. It shouldn't be a problem if I'm generating nWs of 633, but maybe the generation is way down again since I haven't optimized everything after switching the 780 to a fiber. If I still can't see a signal today, I'll try switching back to the old photodiode initially.
'''7/30/14'''
Josh says the 1064 beam is closer to 1200-1400 at the ends, so the 780 beam should be pretty good. I'm trying to measure the power of the 633 beam again but am having difficulty. I can see 633 in the mirror, both right after the diffraction grating and at the end of the PVC tube, but I'm not able to get a signal off the lock-in amplifier. I'm using the same settings as when I originally found the signal. There is a lot of noise and also this doesn't seem to change much when I take out the 633 bandpass filter or when blocking/unblocking the 780 which is surprising since 780 and 633 should be the only signal modulated at 500 Hz.
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