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David Notebook: Difference between revisions
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==Daily Log==
'''1/12/15'''
I briefly was getting the laser to lock for a couple second a few times over the last couple days, but couldn't improve it much. I think I'm seeing pretty good cavity peaks now though--stable and what appear to be a couple free spectral ranges. I want to figure out what kind of piezo is on the laser though, so I can know how much voltage change should give a free spectral range (so I know I'm not way zoomed in on some higher mode stuff).
I can't see anything for a transmitted signal with the PDA10A, without using an amplifier which would reduce the bandwidth too much. I don't see dips on the reflected signal, so this might be part of the locking problem. Maybe I'm not mode matched well enough and aren't getting enough power. I thought it a different lens/cavity position configuration I was seeing peaks on the PDA10A, but that seemed like it had worse mode-matching. Well it was pretty spot on in one dimension, but not even close in the other. Right now it should be pretty close in both, but maybe the last little bit matters a lot and so it was still better overall before. I'm going to re-profile the beam tomorrow and see how close I am and maybe see if I can improve it.
'''1/8/15'''
Nick had the really good idea that my peaks might be so unstable because I wasn't ramping at a high enough frequency (James from Saffman said this can be a problem), and I don't think I was at a high enough amplitude either. I switched to the external ramp and it looks much better now. I think I'm seeing a few free spectral ranges with not much non-0,0 modes, but the reflected signal is very weak (I can't really see it). I'm going to try locking though and see if I can get anything. I'm just using the vescent box for the 1064 cavity beam, so here are the current locking parameters for when I need that to work again:
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