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Message ID: 2204     Entry time: Thu Jun 14 12:00:50 2018
Author: anchal 
Type: Notes 
Category: PMC 
Subject: Latest PMC alignment 

PMC in the North path got misaligned while working on the input path. We aligned it back again today. PMC locking method summary:

  • First increase the incoming power to around 13 mW. Make sure you note down the previous input power so that you can go back to it later.
  • Align the input path in order to see some lissajous figures from the output window. The try to minimize the the output path to a spot.
  • Drive the PMC PZT with signal generator at 5 Hz triangular wave with amplitude enough to transverse one full FSR.
  • Using the transmitted light which can be read from the PD measuring reflection from NCAV, try to supress other modes. TEM00 mode would be the dominant mode. Display this signal on oscilloscope trigered by the signal generator.
  • Once this has been supressed enough, align the reflection off the PMC to the PMC reflection PD. Display this signal also in the oscilloscope and align the input path further to supress all other modes as much as possible.
  • Go back to previous input power, connect back the PZT to the rack and wait for it to get autolocked.

We were able to achieve fringe visibility of 76.16% (measured by VIS program in labs programmable calculator). Also, we were able to get rid of all other modes enough that they were not visible anymore in the oscilloscope.

Keywords for future search: North Cavity Pre Mode Cleaner modecleaner visibility PMC


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