Damage on mirror surface , posted by Manar Amer at Optical room about lasers and optics 
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Following the storage of ~ 50 kW inside the cavity and a sudden drop in transmitted power from the cavity
damage to the mirror surface was suspected.
We broke vacuum and took images of the surface of the 2 mirrors in the cavity, the spherical and the planar mirror |
Damage on mirror surface , posted by Manar Amer at Optical room about lasers and optics
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Tomorrow will try to shift the injection mirror to avoid hitting the damaged spot.
Manar |
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Damage on mirror surface , posted by Manar Amer at Optical room about lasers and optics
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After discussing, we have decided against shifting the mirror to avoid the time lost.
We changed the injection mirror to a different mirror from Mighty Laser set, Transmission of mirror 80
ppm. (no visible damage at the center of the mirror, only a small scratch on the back) |
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liPower storage In Cavity, posted by Manar Amer at Optical room about lasers and optics
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After changing the mirror M1 and cleaning the 2 mirrors
They were placed in the cavity box (avoiding touching the mounts to not affect the alignment and placing the mirrors as close to the previous
position) |
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Power storage In Cavity, posted by Manar Amer at Optical room about lasers and optics
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The cavity was locked under vacuum, coupling is approximately < 10%
The lock was relatively easy and the usual sign (oscillations on the transmission tail) of high finesse on the transmission signal was not seen.
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Power storage In Cavity, posted by Manar Amer at Optical room about lasers and optics
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We improved the lock using the alignment, polarization and CEP , the maximum we got was ~ 12% coupling
only the second stage is on !
Decision : this is the maximum we can obtain using the M1 from mighty laser |
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Damage on mirror surface , posted by Manar Amer at Optical room about lasers and optics
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a better image of the damaged spot, image taken with the arrow for the reflective surface facing the other direction (image shows position)
The image of M1 for ThomX reflective surface was taken at min zoom (full image scale 13 mm) and max zoom (full image scale 2 mm) on microscope
The spot appears to be not close to the center of the mirror, at max zoom in the center we do not see the spot it is just out of the image |
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Damage on mirror surface , posted by Manar Amer at Optical room about lasers and optics
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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. |
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M1 ThomX used while shifted from damaged spot , posted by Manar Amer at Optical room about lasers and optics
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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 |
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M1 ThomX used while shifted from damaged spot , posted by Manar Amer at Optical room about lasers and optics
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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 |
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M1 ThomX used while shifted from damaged spot , posted by Manar Amer at Optical room about lasers and optics
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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 ) |
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M1 Gamma Factory, posted by Manar Amer at Optical room about lasers and optics
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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 |
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M2 ThomX spherical Cleaning , posted by Manar Amer at Optical room about lasers and optics 6x
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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. |
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Cavity polarization states (Koheras), Finesse of 2 polarization states, posted by Loïc Amoudry at Optical room about lasers and optics
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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 |
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Phase measurement with HASO, posted by Loïc Amoudry at Optical room about lasers and optics
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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. |
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Phase measurement with HASO, posted by Loïc Amoudry at Optical room about lasers and optics 8x
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* 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 |
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Phase measurement with HASO, posted by Loïc Amoudry at Optical room about lasers and optics
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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 |
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Polarization optimization, posted by Loïc Amoudry at Optical room about lasers and optics
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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. |
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Record power-up, posted by Loïc Amoudry at Optical room about lasers and optics
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Measurement made on 03/10/18 (nothing has been done since there).
Stable power in the cavity of 225 kW.
3rd stage current
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Motors for D-shaped mirrors, posted by Loïc Amoudry at Optical room about mechanics | lasers and optics
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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. |