Zjs log

--Zjsimmons (talk) 18:25, 8 May 2014 (CDT)

• examined Josh's lockbox. It seems to short the positive rail momentarily when first connected to power and then recover. Very strange behavior. Occurs w/ ICs removed as well, so it doesn't seem to be the chips. Checked voltage ref pots, doesn't seem to be for example shorted diodes. curious.

• Having trouble tuning up the SHG cavity, could not get very nice clean modes, always some garbage in between peaks. Subsequently spun the fiber launch and totally misaligned the whole shebang. I guess it will be good practice tuning it up. Still unable to get as clean of 'troughs' between peaks, may have to pick Nick's brain about it.

--Zjsimmons (talk) 17:30, 7 May 2014 (CDT)

• Tried repairing the fault finder today. Turns out there are some optics inside, two elements in small brass rings, one attached to the laser. Looks like they were glued together at one time and had since broken loose. This was why we could not get light through fibers with the fault finder, even though it was on, it was not correctly launching into fibers. I aligned the two elements as best i could using the transmission through a multi-mode fiber and glued it back together. It sort of works, coupling to single mode fiber is not that great, but with a little fussing(rotating the fault finder and pulling the fiber out slightly) you can get a decent amount of light through a single mode fiber. We should probably get a new fault finder as I don't know how reliable this repair will be.

• re: mysterious polarization noise, could it be we are blocking the beam with our fingers/fiber and that's why the power goes to zero?

• Nick showed me how to tune up the SHG cavity today. It didn't seem too bad to mess with; it'll be good to not be afraid to adjust it.

--Zjsimmons (talk) 23:23, 6 May 2014 (CDT)

• Figured out that the flat polished fibers were the cause of power fluctuations after the TA in 1055nm set-up. Using an angle polished fiber fixed the issue.
• Power fluctuations are also not the reason the circuit is not locking the SHG cavity. Perhaps the gain roll-off needs to be at lower freq? as we are seeing some wiggles around 420Hz (piezo resonance freq). Maybe this is involved in failure to lock. We could also try adding fast feedback branch and see what happens.

4-6-2014 How about a log? Maybe this would work better that the paper lab notebook. Lab notebook seems ill-suited to many functions and i find myself not looking forward to using it, perhaps this will work better. Should be a more natural medium for computer-generated material. It's nice that it would be searchable as well. It could also host PDFs and reports and other documents. I kind of wish we would have started a wiki a while ago! -z