Menhir Pulsed Laser, posted by Manar Amer at Optical room about mechanics | lasers and optics | detectors and electronics 
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The SBox Length (FSR), was changed to match the repetition rate of the Menhir pulsed laser Frep = 216.6625 MHz
It was changed by removing the 2 D-shaped mirrors placed between M1 and M2, distance between M1-M2 ~= 169 mm
it was still needed to be adjusted with M1 motor to reach the correct FSR. |
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Menhir 216MHz laser, posted by Alice Renaux at Optical room about lasers and optics
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The Menhir 216MHz laser has been put back in place on the cavity table. Its output power is measured to be 160mW with an attenuator. Its spectrum is
available in "spectre.xlsx" and "spectre.png". The main wavelength is a bit shorter (1028.75nm) and the spectrum a bit narrower (4.73nm)
than expected. |
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Menhir 160MHz laser, posted by Alice Renaux at Optical room about lasers and optics
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The Menhir 160MHz has been put back in place on the CELIA amplifier setup. Its output power is measured to be 150-160mW with an attenuator as expected.
Its spectrum is available in "spectre_avant_cvbg.xlsx" and "spectre_avant_cvbg.png".
The pulses are stretched by means of a CVBG. Their spectrum is available in "spectre_apres_cvbg.xlsx" and "spectre_apres_cvbg.png". |
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Meeting with LMA people, AFM, posted by Loïc Amoudry at Other about lasers and optics
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30/01/19 - The following powerpoint shows the results discussed with LMA people.
What came out from the discussion is:
- Their cleaning method uses demineralized water drop on a spinner. It is probably the explanation of the circular traces on the mirror's |
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M4 transmission measurement, posted by Loïc Amoudry at Optical room about lasers and optics
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The kept transmission for M4 is 2.17 ppm. Which is the value measured after alignement (center of the mirror).
These measurements have been taken before alignement.
I (A)
Input power (mW)
Transmitted |
M4 transmission measurement, posted by Loïc Amoudry at Optical room about lasers and optics
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Loïc
Amoudry wrote:
The kept transmission for M4 is 2.17 ppm. Which
is the value measured after alignement (center of the mirror). |
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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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M1 transmission measurement, posted by Loïc Amoudry at Optical room about lasers and optics
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Center of M1:
I (A)
Input power (mW)
Transmitted
power (mW)
Transmission (ppm)
0
78
0.01477
189
4
16500
3.2
194
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M1 transmission measurement, posted by Loïc Amoudry at Optical room about lasers and optics
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At different positions, transmission give 194, 193, 208, 200 ppm?
Loïc
Amoudry wrote:
Center of M1: |
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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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Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
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Today we managed to observe the fundamental mode and stabilize the scan on it until we improved the alignment enough.
We see some coupling, but it is very week < 5% , We improved the alignment and the polarization, but there is still no explanation to why
it is very low. |
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Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
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Today, we played on the CEP but using the I-tune input of the Menhir Laser (+/- 5V maximal range).
unfortunately, one only saw a very weak improvement of the transmission by 10-20%... and the coupling improvement is almost zero.
the best improvement was for the maximal I-tune range (+5V) which maybe means that we could improve more the effect if were able to get a full |
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Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
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We played on the CEP using the USB command "id0=xxxxx" of the Menhir.
we put id0=48650 and we improved A LOT the transmission and coupling (~ 60%)
here is an image of the first attempts to lock... but the locking is quite difficult. |
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Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
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We managed to lock the cavity by adding the AOM , but the lock is still difficult to stabilize.
There is some high frequency compensated by the AOM at ~ 170 kHz (yet to understand from where it comes from)
Manar |
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Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
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We wanted to increase the power of the amplifier to measure the transmission output at M2,
but locking the cavity again was very, very difficult.
We will try again tomorrow. |
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Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
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We locked the cavity, and it is stable using the Transmission,
the high frequency that we thought could have a reason for instability, is due to the high power on the photo diode of the PDH box which can
cause non-linearity effects in the signal. |
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Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
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image of the lock with Coupling of ~ 60%
Manar |