Damage on mirror surface , posted by Manar Amer at Optical room about lasers and optics
|
ThomX injection mirror has been cleaned and placed again inside the optical cavity.
This time to avoid the damaged spot I have displaced the mirror mount horizontally to have a distance between center of the beam and the spot
~ 2.5 - 3 mm. |
M1 ThomX used while shifted from damaged spot , posted by Manar Amer at Optical room about lasers and optics 
|
Yesterday , we locked the cavity and we see a sign of a high finesse on the transmission signal, but no measurement of Finesse was done.
we have a coupling of ~ 45%, which is a loss of 20% from the previous coupling of 60%
an estimate done by Ronic MATLAB simulation for the coupling drop where we have 200 pp additional losses and gain of 2.6 k we should get a transmission |
|
M1 ThomX used while shifted from damaged spot , posted by Manar Amer at Optical room about lasers and optics
|
To compare between the 2 images of the cavity mode:
the mode by itself has an integration time of 0.06 ms, position (x, y) = (1142.969, -53.932) um on the beam profiler
the
mode saturated with the spot next to it almost at max intensity has an integration time of 50 ms, position (-3700, -2000) um
comparing |
|
M1 ThomX used while shifted from damaged spot , posted by Manar Amer at Optical room about lasers and optics
|
On Wednesday 21st , I opened the cavity did an additional 2 mm shift of the injection mirror and put it under vacuum again.
Locked the cavity, and observed the transmitted beam.
The second spot is still visible on the beam profiler , the distance difference between the 2 spots is ~ 5.2 mm (the same as before ) |
|
M1 Gamma Factory, posted by Manar Amer at Optical room about lasers and optics
|
In the morning, Vacuum broken and rotated M1 ThomX 90 degrees clockwise, locked the cavity in air and we observe a degeneracy close to the fundamental
mode.
In the afternoon, I cleaned M1 from Gamma factory using pure ethanol and pure water with the spincoater |
|
M2 ThomX spherical Cleaning , posted by Manar Amer at Optical room about lasers and optics 6x
|
Today, M2 Spherical-3 from ThomX that was installed inside the SBox was removed, there was one big dust on the surface of the mirror, mirror was cleaned
using pure ethanol and pure water with spincoater. (images taken with arrow far from us)
M1 from Gamma factory, fixed with the addition of the ring with 3 screws. |
Cavity polarization states (Koheras), Finesse of 2 polarization states, posted by Loïc Amoudry at Optical room about lasers and optics
|
Measurments of Finesse with the 2 polarization states, let's call them H (higher) and L (lower): 24500 for the H and 23500 for the L.
We checked the polarization states in transmission of the FP cavity after a PBS. The H was stronger in PBS trans and the L stronger in PBS ref.
We measured the power in reflection of the PBS and added a half WP that we aligned with the PBS polarization. Then, to get the maximum power |
|
Phase measurement with HASO, posted by Loïc Amoudry at Optical room about lasers and optics
|
2 measurement.
First one locked, in transmission of M2 with 2nd stage 0A.Total 89 cm from the big waist (planar mirrors). 2 wedges used.
Second one at input beam with the same power. Datas taken at the same equivalent position than the first one. 3 wedges used. |
|
Phase measurement with HASO, posted by Loïc Amoudry at Optical room about lasers and optics 8x
|
* Loic has to fix the number of files (3) regarding the number of measurements (2)
* splitted Intensity and phase HASO files
* image for each file |
|
Phase measurement with HASO, posted by Loïc Amoudry at Optical room about lasers and optics
|
with just intensity, the coupling is 98%, and with phase, x direction coupling is 95%, y direction 97%, so the telescope is good.
Loïc
Amoudry wrote:
* Loic has to fix the number of files (3) regarding the number of |
|
Polarization optimization, posted by Loïc Amoudry at Optical room about lasers and optics
|
Optimization of the polarization has been made the 03/10/18. Checked in reflection of the cavity in reflection&transmission of a PBS, locked and
unlocked. Only with 2nd stage.
Ratio values are reflection of PBS divided by transmission or the opposite. |
|
Record power-up, posted by Loïc Amoudry at Optical room about lasers and optics
|
Measurement made on 03/10/18 (nothing has been done since there).
Stable power in the cavity of 225 kW.
3rd stage current
|
|
Motors for D-shaped mirrors, posted by Loïc Amoudry at Optical room about mechanics | lasers and optics
|
Motors have been installed on 16/10/18. No problem with them.
Effect of the motors tested on 17/10/18. No improvement. But they give the possibility to perfectly cut HOM or let them go through as show
the following picture of a 2.2 mode at ~340 mW in trans and 70% coupling @4A. |
|
Transmission vs D-shape position at different powe, posted by Loïc Amoudry at Optical room about lasers and optics
|
Measurements have been done on 18/10/18.
Datas are on excel file, also matlab file. |
|
Beam size vs D-shape position, posted by Loïc Amoudry at Optical room about lasers and optics
|
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. |
|
Beam size vs D-shape position, posted by Loïc Amoudry at Optical room about lasers and optics
|
Matlab code for size vs position and power :
clear all
close all |
|
Power measurement with D-shape, posted by Loïc Amoudry at Optical room about mechanics | lasers and optics
|
Measurements of lot of points with D-shape mirrors well positionned.
Power not optimized to the best but almost. (@4A could have 350 mW).
I (A)
Ptrans (mW)
Coupling |
|
Finesse vs power by difference between main and second resonance, posted by Loïc Amoudry at Optical room about lasers and optics
|
Measurements show that ratio decrease versus power. BUT, the second resonance measurement induce lower power in the cavity so the ratio is not directly
true.
Also, simulation of the main/second resonance power by Pierre's simulation has shown ratio ~50, ~47.6 and 43.5 respectively for 0A, 2A and |
|
Polarization frequency, posted by Loïc Amoudry at Optical room about lasers and optics
|
Check of the frequency of the onefive locked on each polarization of the cavity (tilt a waveplate by 45°).
Frequency repetition rate : 133.335 MHz on spectrum analyzer for both polarization locked. |
|
Polarization frequency, posted by Loïc Amoudry at Optical room about lasers and optics
|
Measurement on 30/10/18.
Loïc
Amoudry wrote:
Check of the frequency of the onefive locked on each polarization |