Hudson Alexander Loughlin - posted 10:18, Wednesday 26 July 2023 - last comment - 14:30, Wednesday 26 July 2023(11247)
Initial Beam Profile of Laser 256 in FermiLab's CMTF
An initial beam profile measurement of laser 256 at Fermilab indicates that it has a waist of 658 +- 173 um located at the front of the laser, a divergence angle of 6.36 +- 0.98 mrad, and a M^2 value of 6.17 +- 1.88. Since the waist is at the front of the laser and the beam needs to be attenuated before measuring it, I couldn't get any data points within 1 Rayleigh range of the waist, so the measured M^2 value is likely far from the true value.
I measured the beam with a Thorlabs DCC1545M CCD camera and used the laserbeamsize python package to measure D4sigma beam diameters and characterize the beam waist, divergence, and M^2. The attached image shows the measured data and calculated beam parameters.
Images attached to this report
Comments related to this report
I added a 150mm lens to focus the beam and get a more accurate measure of the beam quality. With this lens, the beam has a waist of 98 +- 26um and a beam quality factor of M^2 = 0.93 +- 0.24, which is consistent with the true value of M^2 being nearly unity.
The attached image gives more details about the beam characteristics. The reference point for z = 0 is the 150mm lens.
Images attached to this comment
The thorlabs camera has a pixel size of 5.2um X 5.2um which was used to convert units from pixels to millimeters.