Nick Brewer: Difference between revisions

[[Zjs log|Zach]] got the locking circuit working for the cavity without the PPKTP crystal, but there still seems to be a resonance at the piezo frequency (~420 Hz). I rearranged the cavity and put the crystal in it and set up the analyzer for the locking circuit with some cage mount stuff ordered from Thorlabs. It was tougher to set up the cavity with the crystal. The first attempt or two resulted in the input mirror being tilted much more than what the cavity layout we designed. In the end I determined the best way was to optimize a single pass, then put the cavity mirrors in one by one trying to follow the designed beam path as best as I could. The final mirror I put in was the input coupler. I think it's pretty critical to be hitting the center of the curved mirrors so they don't have to be tilted at extreme angles. I looked at the output of the cavity by putting a microscope slide between the two flat mirrors, this is convenient to align the cavity because there isn't enough intracavity power to see a transmission through the HR mirrors. Also it doesn't perturb the cavity a huge amount; only minimal realignment is necessary when it is removed. Once I saw a couple passes of IR with the microscope slide I could see a couple passes of the green output and used that to get a rough alignment. I optimized the cavity then by looking at the cavity peaks of the green light. I touched the two mirrors that walked in the input beam very little because for fear of moving the beam path off of the crystal.