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David Notebook: Difference between revisions
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==To Do==
*5/20/14 photodiode entry?
* Write up isolator tuning procedure/enter isolator in equipment section
* Start poster
==Daily Log==
'''5/20/14''' We continued to try to measure the 633 beam using the OSA and a power meter. We still couldn't detect anything, and the power meter measurements put an upperbound on the power in the nW range. The 780 seed laser hadn't been staying single mode very well, which could be reducing 633 generation or spreading it out to nearby wavelengths. We decided to try to fix this before continuing the search for 633. We tracked the 780 problem down to ASE feedback from the TA getting through the isolator and to the seed laser. This was eventually solved (see [[David_Notebook#780_Laser_Notes|780 laser notes]]). We're hoping this will increase 633 generation, and the nW power upperbound might no longer be accurate. We will look using the OSA and power meter again tomorrow and also using a photo-diode with high gain, which might be more sensitive. We swapped the ________ photodiode and unplugged the 1555 reflected signal, which we will try to remember in a couple weeks when it doesn't work.
'''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.
There should be about 2 mW of power going into the TA, although 5-10 mW should be fine if the output power still isn't at 1W with the current around 2 amps.
'''5/20/14''' Seed laser for the TA was very multi-mode. We eventually tracked the issue down to feedback from ASE due to the TA.
'''5/19/14''' Having difficulty seeing 633 nm generation from the 780 TA beam, but realized that the TA can actually take more current than we previously thought. Increased current to 2 amps and adjusted waveplate to give about 3.3 mW of seed power. Current for the seed is still at 65 mA. Output from the TA increased from about 500 mW to 1000 mW.
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