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--[[User:Zjsimmons|Zjsimmons]] ([[User talk:Zjsimmons|talk]]) 16:45, 7 July 2014 (CDT)
Trying to nail down why the locked laser is misbehaving. The symptoms:
*The lock is stable, but the transmitted IR laser power is not constant but modulated about about 200Hz with a modulation depth of about 50%. The The error signal has a saw-tooth characteristic. This causes significant problems to the output green power as the SHG basically exaggerates the problem and we see pulsed green output instead of continuous green. We have observed the problem go away but we don't know what caused it to disappear.
*Additionally, when scanning the DC offset, the shape of the transmitted resonance changes it noticeably broadens depending on the DC offset. This may or may not be related to the modulation problem.
*When zooming in on a peak with the DC offset and ramp size, as you get very close, the peak looks crappy, there is a lot of structure present which at least part of is at the piezo resonance frequency.
:*Tried replacing the lock-box ramp with an external ramp, the appearance of the peak when you zoom in is perhaps slightly cleaner, but about the same.
:*Tried turning the waveplate on the cube that separates the polarizations for the two photodiode channels and then adjusting the error signal with the lock-box. This did not seem to help or change anything.
:*Perhaps it's a cavity alignment issue? Could going to transmission mode help?
--[[User:Zjsimmons|Zjsimmons]] ([[User talk:Zjsimmons|talk]]) 20:01, 3 July 2014 (CDT)
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