Quote: 
Andrew and I set up the razor blade beam profiling experiment for HeNe lasers on the "SP" table. Once I receive the laser safety training, I will make power measurements and fit it to an erfc curve from which I will calculate the gaussian profile of the beam. I'm attaching some pictures of the setup.
Least count of the micrometer  2 microns
Laser : Lumentum 22037130:1103P
Photodetector : Thor Labs PDA100A

I had measured the yprofile of the beam of Friday at 5 axial locations and fit them to an erfc function using the lsqcurvefit function of MATLAB.
The results were as follows 
z(cm) w (in)
4 0.0131
10 0.0132
15 0.0137
20 0.0139
25 0.0147
I left w in inches in the intensity plots as MATLAB gave more accurate fits for those values.
I converted these to S.I while making the spotsize vs z plot and the corresponding values in microns were
332.74, 335.28, 347.98, 353.06, 373.38.
On fitting these values to the formula for the spot size of a Gaussian beam, the beam waist came out to be 330.54 microns and the location of the beam waist was at z=2cm, where z=0 marks the head of the laser.
TODO : Measure the spot size of the beam at more axial points to obtain a better fit.
Measure the xprofile of the beam.
Analyse the error in the spot sizes and corresponding error in the beam waist.
