Telescope for compressors and ThomX, posted by Loïc Amoudry at Optical room about lasers and optics
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CVBGs telescope is done with w ~= 1mm.
ThomX telescope is done with w ~= 2.3mm in x and y.
Newt step is to lock with these short pulses (measured ~2.5ps with FWHM standard deviation interference method). |
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Onefive output power, posted by Loïc Amoudry at Optical room about lasers and optics
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The pump voltage has been increased few days ago when looking for a modlock of the laser.
The 33MHz Onefive output power is now 3.58mW with OD1 filter ==> ~36mW.
There are 2µW @ 1% coupling fiber with OD1 filter ==> ~20µW ==> 2mW @99% coupling fiber (2mW to the amplifier). |
Onefive output power, posted by Loïc Amoudry at Optical room about lasers and optics
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Onefive output power measured today. 3.52 mW with OD1 filter ==> ~35mW.
Loïc
Amoudry wrote:
The pump voltage has been increased few days ago when looking for |
CVBG reference and Eric Cormier calculation, posted by Loïc Amoudry at Optical room about lasers and optics 
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The Stretcher is the "D 24-02-II", it must be used in double path before the amplifier injection.
There are two compressors in single path, "D 25-14-I" and "D 25-14-II".
Eric calculations are attached below. |
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30Hz noise issue, posted by Ronic Chiche at Optical room about lasers and optics | detectors and electronics
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since some days, we observe the cavity is difficult to lock and a strange 30Hz noise has appeared on the PZT signal which normally compensate the phase
noise difference between the cavity and the laser.
to test if the problem could come from the laser, we changed the OneFive laser for the Koheras but we have exactly the same problem, thus we concluded |
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30Hz noise issue, posted by Ronic Chiche at Optical room about lasers and optics | detectors and electronics
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The 30 Hz noise issue has been solved !
It came from translation stage of P1 and/or P4.
Fabian remembered that close to the mirror's mount translation stage end coarse, there is a mechanical instability. The mount kind of "lift |
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Pneumatic valves, posted by Loïc Amoudry at Optical room about vacuum
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The pneumatic valves are now plugged on the university air network.
The air valve is fully openned for the moment.
We still have to check if there is some minor leakage close to the pneumatic valve to improve the setup. |
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First Lock with 2nd satge of amplifier : Motor issue ? , posted by Ronic Chiche at Optical room about mechanics
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Global locking almost clean : tranmission and reflection are quite noiseless except the peaks at every 500ms.
During the amplifier 2nd stage lock, we experienced 2 strange behaviors :
- short "unlocks" every 500ms exactly all the time, during the whole lock process |
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First Lock with 2nd satge of amplifier : Motor issue ? , posted by Ronic Chiche at Optical room about mechanics
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The 500 ms noise disapeared. We had to disable the "power save" mode of the smaract translation stage. AND turn OFF and ON the controler box.
Ronic
Chiche wrote:
Global locking almost clean : tranmission and reflection are quite |
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Onefive Origami 33MHz specs, posted by Loïc Amoudry at Optical room about lasers and optics 6x
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Power during ~20h, power after turn on, spectrum image and excel datas, polarisation and pulse length.
Powermeter measurments were done with a /10 filter.. 3 mW means 30 mW
Important: Onefive does not automatically locks after being turned on. |
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Onefive Origami 33MHz specs, posted by Loïc Amoudry at Optical room about lasers and optics
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Beam Size Onefive added
Loïc
Amoudry wrote:
Power during ~20h, power after turn on, spectrum image and excel |
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Spherical mirrors at closest position. FSR, finesse and beam size., posted by Loïc Amoudry at Optical room about lasers and optics
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The spherical mirrors are at the closest position to get a FSR ~=33.3435 MHz. Planar mirrors are at the largest position.
The finesse has been measured about 17 000.
Beam diameter (2*w) is ~= 4.6 mm x and y. |
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First mode degeneracy on ThomX, posted by Loïc Amoudry at Optical room about lasers and optics
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Yesterday, we've observed the first degeneracy on ThomX cavity at ~115 kW stored. The shape of the stored power on the oscilloscope is really close
to what has been published in the D-shape mirror's paper ("tek0000" transmission in yellow, piezoelectric activator in green, error
signal in blue). |
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New locking scheme, posted by Ronic Chiche at Optical room about detectors and electronics
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Before, the locking scheme was to produce an error signal with the PDH box, send its output to the electronic amplifier box and then to the laser EOM
for the fast loop and to the Laselock input. The drawback was changing one loop gain, changes also the other loop gain.
Now, the locking scheme is the error signal coming from the PDH box is directly sent to the Laselock input and in a same time to the electronic |
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First Lock with 2nd satge of amplifier : Finesse issue ?, posted by Ronic Chiche at Optical room about lasers and optics | detectors and electronics
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1st lock today with the second stage of the amplifier.
~ 300mW of injected power (but which proportion of the pump and of the signal ? => One must use a spectrometer to determine this proportion)
MAYBE the real injected power of the signal is lower => maybe the Finesse is higher ! |
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First Lock with 2nd satge of amplifier : Finesse issue ?, posted by Ronic Chiche at Optical room about lasers and optics | detectors and electronics
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First of all, we used and optical spectrometer to determine which proportion of pump and signal is in the injected beam.
the wavelength is THE SAME for the 2nd stage for the beam coming from the core or coming from the clad !
thus, it is impossible to use a spectrometer to obtain this proportion. |
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Onefive spectrum and CVBG spectrum, posted by Loïc Amoudry at Optical room about lasers and optics
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| The Onefive spectrum has shifted a little bit to lower lambda. It's still enough for the experiment (3mW injection of ampli intead of 1mW needed). |
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Fiber injection and onefive output power, posted by Loïc Amoudry at Optical room about lasers and optics
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Fiber injection is finished with the new ThomX stretching CVBG in double pass (+50% injection power compared to K-BOX CVBG in simple pass).
- Output Onefive: 27 mW
- After Onefive + lambda/2 + isolator: 25.8 mW |
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Free Spectral Range (FSR), posted by Loïc Amoudry at Optical room about lasers and optics
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FSR is 33.347 MHz @1e-8 mbar
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Improvement holder amplifier fiber, posted by Loïc Amoudry at Optical room about lasers and optics
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| We've added a clamp in the 3rd stage to prevent the pump fiber from moving and tilting (it was tilting to the left). |
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ThomX amplifier M2, posted by Loïc Amoudry at Optical room about lasers and optics
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| The ThomX M2 has been measured between 1.5-1.6 for x and y |
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Electrical trouble (disjunction), posted by Loïc Amoudry at Optical room about cabling
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The circuit breaker on ThomX cavity drops @1.5-1.8kW when we turn on 1/2nd stage of the amplifier or 3rd stage of the amplifier.
Amplifiers are now connected to K-BOX UPS.
We are buying a clamp ammeter for further investigations. |
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Cavity under vacuum , posted by Loïc Amoudry at Optical room about vacuum
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The cavity is right now at 6.5e-8 mbar (turbo pumps on for 1 night and ionic pumps for 3h), primary pumps and turbo pumps are cut, ionic pump are on
and the pressure level is still going down.
Therefore there aren't any big leak in the cavity and we can expect a final vacuum level close to e-9 mbar. |
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Pneumatic valves, posted by Loïc Amoudry at Optical room about mechanics
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| Frederic and Manu from vacuum group came this morning to fix again the pneumatic valves which had a leak again. |
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Finesse measurement, posted by Ronic Chiche at Optical room about lasers and optics
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After mirrors were going back from LMA for cleaning and thermal anealing, they have been installed in FP cavity for Finesse measurement.
after getting strange results when the cavity is closed (very low Finesse...maybe too much ethanol inside cavity procucing some lineic losses),
we get 12k-12k5 Finesse with primary vacuum (~4 mbar) and a clean lock (very flat transmission signal and quite noiseless reflection signal) |
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Finesse measurement, posted by Ronic Chiche at Optical room about lasers and optics
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To complete these observations:
Finesse has been measured on thursday, right after cleaning the cavity with ethanol @6000.
Finesse has been measured on friday, after opening the cavity for few tens of minutes @12000-12500. The cavity was openned while |