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Entry  Mon Aug 3 13:10:46 2020, shruti, DailyProgress, Lab Work, Initial experiments and prep IMG_633BBA57553C-1.jpeg
    Reply  Tue Aug 4 14:08:44 2020, shruti, DailyProgress, Lab Work, Initial experiments and prep: Beam profile IMG_0268.jpgErf.pdfDiv.pdfbeamprofdata.zipIMG_0258.jpg
Message ID: 2549     Entry time: Tue Aug 4 14:08:44 2020     In reply to: 2548
Author: shruti 
Type: DailyProgress 
Category: Lab Work 
Subject: Initial experiments and prep: Beam profile 

Notice of lab entry: I will be at the cryo lab for a few hours today (04 Aug 20) afternoon


Beam profile results [razor-blade method]

At a few locations along the beam I measured the vertical and horizontal beam radii by measuring the power at different positions of blade edge across the beam. The power measured at the photo-diode was fitted with  a + b \times {\rm erf}(\sqrt{2}(x-x_0)/w_z)) where w_z is the beam radius at the location along the beam and x was either the horizontal or vertical position of the blade.


The standard deviation as estimated from the fits are lower than \pm0.002 mm for all estimated radii.

But with the crude nature of the setup and not having the laser temperature stabilized (resulting in power drifts while taking readings), I guess that the error in each measurement is higher. The data in Attachment 3 also has recorded the resistance of the temperature sensor at different points while taking the data.

Beam radii
Distance [in.] Horizontal radius [mm] Vertical radius [mm]
5 \pm 0.1 0.120 0.121
6 \pm 0.1 0.146 0.150
7 \pm 0.1 0.175 0.173
8 \pm 0.1 0.203 0.200
9 \pm 0.1 0.231 0.229


- Attachment 1 has the updated setup with the clamped translation stage

- Attachment 2 shows the measured points with the error function fits. The offsets between the different curves along the x-axis are arbitrary.

- Attachment 3 shows a linear fit and an estimated divergence angle. I've assumed that all points I measured are outside the Rayleigh range, i.e., away the beam waist. The caption '5H' means that this set of data was taken 5 inches away from the output coupler (fibre-to-free space) moving the blade in the horizontal direction.

- Attachment 4 has all the data and jupyter notebook with analysis

- Attachment 5 shows the beam spot on the view card

Attachment 1: IMG_0268.jpg  2.834 MB  Uploaded Thu Aug 6 14:07:36 2020  | Hide | Hide all
Attachment 2: Erf.pdf  20 kB  Uploaded Thu Aug 6 14:11:07 2020  | Hide | Hide all
Attachment 3: Div.pdf  13 kB  Uploaded Thu Aug 6 14:11:16 2020  | Hide | Hide all
Attachment 4: beamprofdata.zip  109 kB  Uploaded Thu Aug 6 14:11:40 2020
Attachment 5: IMG_0258.jpg  2.202 MB  Uploaded Thu Aug 6 14:23:22 2020  | Hide | Hide all
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