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Message ID: 718     Entry time: Wed Apr 7 19:12:47 2010
Author: Zach 
Type: Laser 
Category: GYRO 
Subject: Y1S reflectivities 

 This morning, I realigned the CW beam path through the AOM and then into the cavity. I was able to isolate the TEM00 to some decent degree, but there is still a bunch of higher order crap visible (likely due to the fact that we are no longer using the optimum modulation frequency of ~33 MHz---see Alastair's previous post).

In doing so, I was reminded of the issue we have regarding the reflectivities of the (supposedly Y1S) curved mirrors we have in the cavity at the moment. A few weeks ago, Rana, Alastair and I measured the transmission through these to be MUCH higher than they should be. As a result, the impedance matching of the cavity is piss poor.

This afternoon, I measured T for the 9-m Y1Ss that we ordered at the same time. I got T ~ 5e-5 at 45 degrees, which is consistent with Mott's measurement on the wiki. So, either the 6-m mirrors were different or we screwed them up somehow. Our original plan was to use the 9-m ones, so we might as well stick those in and see if our coupling improves. Also, we can start thinking about modematching (not yet, not yet..).


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