David Notebook: Difference between revisions

'''5/19/14''' After initial alignment of 1064, the 633 beam could easily be seen when ramping the cavity without any adjustment. It seems very repeatable, but also suggests that the power isn't close to being optimized yet since there was no noticeable difference in brightness after having a weekend to drift. We spent most of the day trying to increase the 633 beam power so that we can see it on an OSA. First we worked on the 780 alignment, and adjusted it while looking at the 633. A full "beam-walk" was too difficult without some sort of numeric measure of 633 power, but by only adjusting the vertical and horizontal of one mirror we made the 633 substantially brighter. At one point, the 633 signal disappeared (well after the walking process) and moving to different cavity modes didn't help. I'm not sure why this happened, but this was solved by slightly translating and rotating the prism and then adjusting the beam blocks for the 807/780/1064 beams. This was an easy process to get the 633 beam back, which is encouraging.

We also doubled the power of the 780 immediatelyas measured directly after the TA (see [[David_Notebook#780_Laser_Notes|780 laser notes]]). We still couldn't see a signal on the OSA though, even with lots of averaging and with the beam locked. But lookingLooking at the coupling fiber when ramping the cavity, however, we could clearly see the 633 beam flashing above a constant background of 780. Putting in an 780 notch filter and a 633ish bandpass filter (borrowed from 1st floor John), we knownow have what seems to be a flashing 633 signal with very good contrast (i.e. against very little background). The fact that this filter works makes it even more definitive that what we're looking at is 633. We hope that this will be easier to optimize and finally detect with the OSA. It's confusing that the 633 signal is so visible even through the fiber and when not looking directly at it--how sensitive is the eye that sensitive to 633, or could we be having equipment issues?