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David Notebook: Difference between revisions
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==Daily Log==
'''10/8/14'''
I tried to track down where the noise was coming from. The DC error output on the vescent box only is noisy when it's connected to the error signal and the RF is on (doesn't matter whether the laser is on and there is actually an error signal). The full height is about 15 mV of noise. I checked the laser diode output using a photodiode and the noise doesn't seem to be coming from there. Most likely seems the RF amplifier in the circuit, although the low pass filter isn't cutting this as much as I'd think either. I tested the amplifier by itself though and it didn't show any sidebands, which would have been the obvious cause. It does have signals at integer multiples of the input RF signal, but those are all around 10 db lower. I checked the same amplifier on the 1064 setup and it showed similar behavior. The vescent box on the 1064 also shows similar noise with, although slightly less, so maybe nothing is broken and this has always been there.
'''10/7/14'''
Ordered 2 HeNes from Ebay so we can return the ones we've been borrowing from the optics lab. I've been wondering if maybe the amount of optical feedback isn't right for the 1555 locking circuit. I was able to get kind of a lock with only the first integrator on (20 kHz). Then I adjusted the optical feedback and then the proportional gain. The best performance seemed to be between 2-3 V optical feedback when the circuit isn't locked. It's currently set at 2.5V, which will give some locking with the proportional gain course knob 2 clicks up and the fine gain most of the way up.
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