40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  ATF eLog  Not logged in ELOG logo
Message ID: 199     Entry time: Fri Jul 24 16:59:10 2009
Author: Connor 
Type: Laser 
Category: Fiber 
Subject: 1W NPRO minimum extinction ratio 

The 1W NPRO beam is elliptically polarized. We use a quarter-waveplate (QWP) to linearize the polarization.

7 days ago, I made some measurements of the extinction ratio of the beam for various orientations of the QWP (attenuating the beam with a half-waveplate and polarizing beamsplitter) to find the QWP orientation at which the light is linearly polarized. The minimum ratio occured when the fast axis was between 10 and 15 degrees from the vertical. I've attached a plot of the data, and I will fit it to a curve as soon as I work out which function should describe the data.

Attachment 1: ExtRatio1WNPRO.pdf  4 kB  | Hide | Hide all
ExtRatio1WNPRO.pdf
ELOG V3.1.3-