CELIA 100W laser amplifier repair , posted by Ronic Chiche at Optical room about lasers and optics
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this morning with Alice, we sent the Menhir 160MHz injected in a fiber (with 6mW at the end of a long fiber) into the laser amplifier, to look for leakage
or damage in the first stages of the amplifier (the amplifier is totally off).
first of all, we checked for light scattering around the laser crate with a sensitive optical card => nothing |
CELIA 100W laser amplifier repair , posted by Ronic Chiche at Optical room about lasers and optics 
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this afternoon, we saw some electric cables badly connected to their power supply.
we fixed it by soldering them together and screwing the result to the power supply.
(see 1st image) |
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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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CELIA 100W laser amplifier repair , posted by Ronic Chiche at Optical room about lasers and optics
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friday morning, we add a zoom call with Jerome Lhermite about the amplifier repair.
he approximately confirmed the amplifier scheme from the Loic thesis.
he suggested to: |
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Alignment of a 2-mirror FP cavity, posted by Ronic Chiche at Optical room about mechanics | lasers and optics
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today with Alice,
- we measured the height of the SBOX windows center : 140mm from the optical table.
- we set the laser fiber colimator exactly at this height. |
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2-mirror cavity alignment, posted by Alice Renaux at Optical room about mechanics | lasers and optics
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At the beginning of the week, I installed a half-wave plate, a beamsplitter cube and a quarter-wave plate, as well as the end-of-cavity mirror, which
I unsuccessfully tried to align.
I removed the end-of-cavity mirror and started the laser injection over again with the two motorized mirrors placed in front of the vacuum chamber |
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2-mirror cavity alignment, posted by Alice Renaux at Optical room about lasers and optics
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Yesterday and today, I replaced the OEWaves CW laser with the NKT CW laser. Its screen does not display anything, so it has to be operated through the
GraphiK software.
I then re-aligned the cavity with a new adjustment adaptation tool between the mirror mounts and the irises. |
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2-mirror cavity alignment, posted by Alice Renaux at Optical room about lasers and optics
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The NKT laser PZT sensitivity is ~0.09pm/V of wavelength variation, which is equivalent to ~ 25MHz/V
So, the full range of the scan is roughly 250MHz (more than a FSR) for 10V.
It seems impossible to get such large resonances unless the Finesse is very low => let's try to change M1 by a spare GammaFactory plan |
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2-mirror cavity full setup, posted by Alice Renaux at Optical room about lasers and optics
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Today with Ronic, we changed the FP cavity's mirrors to Layertek (Gamma Factory) mirrors :
- M1 : n°161186 --> fused silica, unknown absorption, unknown diffusion, T1=2500ppm transmission planar mirror ;
- M2 : n°161182 --> fused silica, unknown absorption, unknown diffusion, T2=10ppm transmission, 5m ROC mirror. |
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first attempt to lock, posted by Ronic Chiche at Optical room about mechanics | lasers and optics | detectors and electronics
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With Alice, we installed the EOWaves oscillator to be locked on the FP-cavity (T1 ~ 2500ppm, T2 ~ 10ppm => F ~ 2500)
FSR = 216MHz => LW = 86kHz.
We installed the PDH box, and we got some error signal, but the shape of the transmission signal and error signal is a bit strange... |
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2-mirror cavity locking, posted by Alice Renaux at Optical room about lasers and optics
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In June, we encountered some problems regarding the transmission and error signals (see images here),
looking as if the laser was switched off before the cavity was filled.
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Successful lock (finally !), posted by Alice Renaux at Optical room about lasers and optics
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Today, with Ronic, we managed to get a successful lock with the NKT laser by setting up a new PDH box from scratch (photodiode + amplifer + mixer).
Me measured the injected power (5.4mW) and the transmitted power (33µW) after a wedge (92% transmission) and a 7ppm transmission mirror,
so the intracavity power was 5.1W. We have a 950 enhancement factor for a 3100 finesse cavity, so a nominal enhancement factor of 2500. The lock was very |
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Finesse measurement, posted by Alice Renaux at Optical room about lasers and optics
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Today, with Ronic, we measured the finesse of the 2-mirror cavity witht the NKT CW laser.
We were able to perfrom the measurement only once, and the results of the measurement are attached to this note. We added sidebands to the laser
spectrum peak thanks to an EOM, and we sweeped the modulation frequency on a 1MHz span around an estimated FSR of 216.63MHz in 10s. We found a 82kHz linewidth, |
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Finesse measurement, posted by Alice Renaux at Optical room about lasers and optics
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(Finesse 2651 is consistent with that obtained from the mirrors' transmission coefficients, which is about 3100.)
Alice
Renaux wrote:
Today, with Ronic, we measured the finesse of the 2-mirror cavity |
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new cavity, posted by Alice Renaux at Optical room about lasers and optics
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Yesterday, we changed the M1 mirror to a 161185 Gamma Factory mirror of transmission 460ppm, the cavity
finesse is now 13360.
We managed to lock it today. |
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new cavity, posted by Alice Renaux at Optical room about lasers and optics
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The 2-mirrors cavity has 460ppm of transmission for M1 and 10ppm for M2 which should exhibit a Finesse around 13400.
Today, we managed to lock the NKT laser (with an AOM for fast feedback) onto the cavity, and we made 5 Finesse measurements with the modulation
technic : 14151, 13847, 13968, 14604, 13892 with an average around 14000 => LW = 216MHz/F ~ 16kHz. |
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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 |