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David Notebook: Difference between revisions
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'''Things to Do/Check'''
Measure 780 power before and after cavity; see changes with cavity piezo
put in diffraction grating (check specs)
make "V" shape with pvc pipes
make "N" shape with pvc pipes
Take out lens and translate photodiode
'''6/11/14'''
We aligned once more with the camera today, and also noticed that the waveplate after the 780 TA was not set optimally to match the polarization of 1064, which would reduce 633 generation efficiency. Fixing this and getting a better alignment of the 1064 beam with the cavity today let us see 633 through the prism again, with about the same level of brightness as previously. We could still not see it through the fiber, but this is likely just a coupling problem so we aren't concerned. We looked at the signal from the photodiode after the prism, and also a pickoff from the 780 TA and found them both to be very correlated with the cavity piezo movement. The 780 seed laser still seems stable though. We also found some correlation with the prism photodiode with only the 1064 beam on, so 1064 or a sideband must also be getting through to the photodiode.
The power fluctuations in the 780 TA are small and we don't think they are a problem beyond the difficulty they cause in detecting the 633 signal. We're going to ignore them for now and try to better isolate the 633 signal. We're switching out the prism for a diffraction grating and are going to use two pvc pipes in a "V" shape. Since there's only scattered light getting through and not any beams besides 633, this should greatly reduce noise. We're also going to remove the lens before the photodiode, since this is focusing scattered light too, and instead put the photodiode on a translation stage.
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