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Message ID: 167     Entry time: Thu Jul 9 10:48:03 2009
Author: Connor 
Type: Laser 
Category: Fiber 
Subject: Beamscan for 1w NPRO 

Aidan suggested that we try to characterize the beam width of the 1W NPRO again, this time operating the laser at high power and attenuating the beam with a half-wave plate and a polarizing beam splitter.  I aligned the optics such that at full output power (~1.19W), the power incident on the BeamScan is 145 mW.

There are a number of things I noticed about the beam profile around 10" from the laser aperture that I don't know how to deal with, so I decided not to make measurements until working things out.

While the profile of the beam is much cleaner now than it was before when we measured beam width at low power output, the width of the beam seems to depend on the driving current to the laser.  At 1.2A driving current, the beam diameter was roughly 1650 micrometers.  The width dropped down to around 1300 micrometers at 2A driving current, and then climbed back up to 1500 micrometers at full power output with 2.38A driving current.

Also, as David noted, the beam width fluctuated by up to 40 micrometers when moved to different places on the head.

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