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Message ID: 1190     Entry time: Wed Jan 14 02:38:43 2015
Author: Zach 
Type: Laser 
Category: SiFi 
Subject: PMC set up as test cavity 

To continue with the laser/modulator testing, I have added Dmass's old PMC to the temporary characterization setup. I have used the other output of the 50/50 BS that combines the two laser diode outputs, so that we can keep the beat setup intact while also being able to send either of the two beams into the PMC.

 

To do this, I:

  • Made a cursory razor beam scan of the beam emerging from the BS
  • Calculated a MMT solution to the PMC mode using some of our new lenses
  • Installed the telescope and directed the beam towards the PMC
  • Macropositioned the PMC by hand to rougly center it on the transmission of the single-pass beam, as measured using a power meter
  • Scanned the PZT using a 0-10 V triangle from an SRS function generator, then used the diode temperature as a coarse adjustment to look for modes
  • Maximized the first found mode (a horizontal HOM)
  • Looked for nearby lower-order modes, then maximized them and iterated to get to TEM00
  • Installed HWP upstream and then maximized visibility by rotating polarization

The coupling isn't stellar yet, at roughly ~66%, but the MMT is fairly tight and I'm sure I can improve easily. The laser and cavity are stable to well within a linewidth at high frequencies, and only drift apart over many seconds.

Some things I plan to do with this setup:

  1. Dither lock the PMC to the laser(s)
  2. Characterize the phase modulators
  3. Set up reflection PDH lock and feed back to lasers
  4. More stuff
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