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 ! |
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 |
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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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 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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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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Amplifier output power , posted by Loïc Amoudry at Optical room about lasers and optics
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The ouput power of the ThomX amplifier has been measured as a function of the 3rd stage pumps current (0A is 1st and 2nd stage turned on).
We measured the total power, the total power without the "donuts" pump signal dumped by an iris and the transmission of a dichroic
mirror (for ref see image). |
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Amplifier output power , posted by Loïc Amoudry at Optical room about lasers and optics
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Loïc
Amoudry wrote:
The ouput power of the ThomX amplifier has been measured as a function |
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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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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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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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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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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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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). |
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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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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 |
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Beam pulse duration, posted by Ronic Chiche at Optical room about lasers and optics
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We installed the 2 CVBG for compression after the amplifier.
We used an interferometric technique with a delay line and combining the two paths in a CCD to measure interferences... see interferences.avi video
file |
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Beam pulse duration, posted by Ronic Chiche at Optical room about lasers and optics
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Yesterday, Loic installed a telescope before CVBG's to reduce the spot size on CVBG's and reduced the incident angle 0.5-1° on them (on the
datasheet the specified incident angle is 2.8°).
We used an interferometric technique with a delay line and combining the two paths in a CCD to measure interferences. |
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Beam pulse duration, posted by Ronic Chiche at Optical room about lasers and optics
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Yesterday, Loïc put the CVBG's back to their specified angles.
We used an interferometric technique with a delay line and combining the two paths in a CCD to measure interferences.
After supressing the global shape of the superposed pulses, one measures the amplitude of the remaining fringes (standard deviation) each 50µm |
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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). |