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Entry   Beam size vs D-shape position, posted by Loïc Amoudry at Optical room about lasers and optics 181018_4A_no_cut.PNG
    Reply   Beam size vs D-shape position, posted by Loïc Amoudry at Optical room about lasers and optics size_vs_position_and_power.JPG
Message ID: 10     Entry time: Fri Oct 19 11:46:21 2018     In reply to: 9
 Author: Loïc Amoudry 
 Status: Fixed 
 Type: report 
 Category: lasers and optics 
 Location: Optical room 
 Title: Beam size vs D-shape position 

Matlab code for size vs position and power : 

clear all
close all

x = [1820 1820 1925 1936 2117 2260];
y = [2013 2013 2029 2090 2249 2392];
Position = [0 0.2 0.4 0.6 0.8 1];
Trans = [337 330 306 245 128 17]

hold on
[ax,h1,h2] = plotyy(Position,x,Position,Trans)
set(get(ax(1), 'Ylabel'), 'String', 'Beam diameter (um)');
set(get(ax(2), 'Ylabel'), 'String', 'Transmitted power (mW)');
xlabel('Position of the D-shape (mm)')
plot(Position,y,'g')
hold off

Loïc Amoudry wrote:

Measurement done on 18/10/18.

At high power, the shape of the 0.0 mode does not change. The D-shape only generate losses in the cavity. Then the power stored in the cavity decrease. As with this configuration, the cavity beam size decrease when power increase, the beam size decreased.

Measurements done @4A on 3rd stage.

x (um) y (um) Picomotors displacement (um) Transmission power (mW)
1820 2013 0 337
1820 2013 200 330
1925 2029 400 306
1936 2090 600 245
2117 2249 800 125
2260 2392 1000 17

Then we get the D-shape away from the beam to not cut it and decreased the amplifier power to validate the beam size at a known value. So the power as been decreased to 2A (= 125 mW in trans) and the beam size was x=2079 y=2255, similar to the 125 mW with D-shape mirrors values.

 

Attachment 1: size_vs_position_and_power.JPG  46 kB  | Show | Show all
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