Bots, Bureaucrats, Interface administrators, Suppressors, Administrators, Upload Wizard campaign editors
573
edits
David Notebook: Difference between revisions
Jump to navigation
Jump to search
no edit summary
No edit summary |
No edit summary |
||
|
==Daily Log==
'''7/9/14'''
Testing the 633 filter showed it lets through about 90% of 1555.
Evacuated the cavity and re-aligned 1064. Couldn't see what we've believed to be the 633 beam (as expected) although I couldn't figure out how to re-overlap the 1064 and the 780 beams (usually we use the generated 807 beam, which passes through the dichroic mirror). Hopefully I'll be more clever tomorrow. The 1064 alignment was only marginally more than for a typical morning though, so I don't think it would be moved so much that the 780 wouldn't overlap enough to generate 633 if gas were in the cavity. I found that the signal to the photodiode when locking was actually much higher now--about 20 nW. This happens whether 780 is on or off, so it can only be from 1064. This may suggest it is not 1555 as we suspected, although there is much more 1064 generated when locking with no gas in the cavity (I measured about 200 mW exiting the cavity when locking today), and 1555 might still dominate when there is gas.
Putting the cavity mirror in front of the PVC pipe drops the signal by a factor of 50 to .4 nW (was I off by a factor of 10 when I checked with gas in the cavity? I don't think so, but maybe recheck).
Since the signals when locking don't seem to be from 633, the .4 amps/watt value I've been using for the photodiode to calculate powers is probably incorrect. For 1064, it is closer to .25 (so powers are actually higher), and it is unrated at 1555. Still, the relative power drops are useful.
So at least some of the locking signal is from 1064, and some is likely to be 1555 as well. The cavity mirror helps and other filters probably would as well, but it still seems the best option is to use the beam chopper.
| |||