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Message ID: 132     Entry time: Thu Sep 29 15:40:45 2016
Author: Gabriele 
Type: Optics 
Category: Design 
Subject: Beam profile of new 21mW HeNe laser and tweak of optical lever design 

I measured the beam profile of the new Thorlabs HeNe (21.8 mW measured). The beam waist is 355 microns, very close to the laser output port.

Using those numbers and the optical gain optimization algorithm, I tweaked the optical lever design. The simplest solution uses two lenses right after the laser to focus the beam down to about 300 microns on the QPD. The arm lever length is about 1.6 m, corresponding to an optical gain of about 18000/rad. I updated the DCC drawing in D1600213

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