Cavity beam axis moving with power, posted by Ronic Chiche at Optical room about lasers and optics 9x
|
how the cavity beam axis is moving during a lock when the cavity is hot ?
could it explain a part of the Transmission / Coupling signal decay ?
we placed 2 Basler camera, one at (30+Z) cm and the other at (85+Z) cm (Z is about 15cm) from the M3 mirror, we recorded the video during a lock |
|
Cavity Lock , posted by Manar Amer at Optical room about lasers and optics | detectors and electronics | software
|
Start with the cavity lock images attached, taken from last week, at start we have a coupling ~ 5% and started improving on the
alignment .
The image of 00 modes attached corresponds to the coupling seen on the oscilloscope. |
Cavity Lock , posted by Manar Amer at Optical room about lasers and optics | detectors and electronics | software
|
Current setup at SBox for locking the cavity
After spacial matching, the coupling increased to ~ 15 - 20 %
The locking was done for the fundamental mode, tried to improve the coupling with the motors, but the lock is very unstable to be investigated. |
|
Cavity Lock , posted by Manar Amer at Optical room about lasers and optics | detectors and electronics | software
|
Cavity locked today under vacuum and no airflow, it is stable over a long time
the alignment was improved and an increase of the transmission by 20 % from its original value
unfortunately, data from the oscilloscope was saved, but it was not in the correct format (image) to show. |
|
Cavity Lock , posted by Manar Amer at Optical room about lasers and optics | detectors and electronics | software
|
Closing the series for the setup
The cavity was only locked @ 133.33 MHz but the Finesse was not measured
The FSR was changed to match the new laser MENHIR 216.6625 MHz |
|
CVBG stretching / Fiber Injection , posted by Manar Amer at Optical room about lasers and optics | detectors and electronics | software 7x
|
Before injecting into the amplifier, the pulse needs to be stretched using a CVBG, type attached.
the CVBG is to be used at a small angle, the beam shape and spectrum after the PBS is attached.
After measuring the beam profile, a mirror was placed to direct all the power for fiber injection |
|
CVBG stretching / Fiber Injection , posted by Manar Amer at Optical room about lasers and optics | detectors and electronics | software
|
closing series
Manar
Amer wrote:
Before injecting into the amplifier, the pulse needs to be stretched |
|
CFBG removed from ThomX CELIA amplifier, posted by Loïc Amoudry at Optical room about lasers and optics
|
The CFBG has been removed successfully and the amplifier is closed now.
The soldering machine had a calibration trouble and was sent to the company for review during holidays.
The output power has been checked and is the same as before (tested until 30W ouput power). |
|
CELIA amplifier installation + chiller, posted by Manar Amer at Optical room about lasers and optics | detectors and electronics | software
|
Amplifier placed next to the pulsed laser on the table under the airflow
The output is in free space with height from the table of about 10 cm, note the injection height into the cavity is between 14 - 15 cm.
a power cable is placed but not plugged. |
|
CELIA amplifier installation + chiller, posted by Manar Amer at Optical room about lasers and optics | detectors and electronics | software
|
The software to control the CELIA amplifier is on the laptop that was placed in ThomX bunker.
I have placed it in the PLIC room next to the SBox table.
it is called 'Alphanov Control Software' |
|
CELIA amplifier installation + chiller, posted by Manar Amer at Optical room about lasers and optics | detectors and electronics | software
|
Closing series
Manar
Amer wrote:
The software to control the CELIA amplifier is on the laptop that was |
|
CELIA amplifier installation, posted by Manar Amer at Optical room about lasers and optics | detectors and electronics | software
|
The amplifier was installed on the optical table next to SBox table.
The CVBG that will be used for stretching before amplification needs cleaning (they are very fragile, 'ask victor for best method')
The software to drive the diodes of the amplifier we have is not the compatible one. |
|
CELIA 100W laser amplifier repair , posted by Ronic Chiche at Optical room about lasers and optics
|
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
|
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) |
|
CELIA 100W laser amplifier repair , posted by Ronic Chiche at Optical room about lasers and optics
|
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: |
|
Beam size vs D-shape position, posted by Loïc Amoudry at Optical room about lasers and optics
|
Measurement done on 18/10/18.
At high power, the shape of the 0.0 mode does not change. The D-shape only generate losses in the cavity. Then the power stored in the cavity
decrease. As with this configuration, the cavity beam size decrease when power increase, the beam size decreased. |
|
Beam size vs D-shape position, posted by Loïc Amoudry at Optical room about lasers and optics
|
Matlab code for size vs position and power :
clear all
close all |
|
Beam size behind M2, posted by Ronic Chiche at Optical room about lasers and optics
|
Beam diameter behind M2 :
- 2nd stage @ 6A - 1kW inside cavity
sx = 2120 µm |
|
Beam size behind M2, posted by Ronic Chiche at Optical room about lasers and optics
|
the telescope matchs the cold cavity beam, so it is normal to have a power decrease on the transmission photodiode when the cavity is heating at high
power.
we can try to adjust the telescope by moving lens, one by one, to increase the cavity power. |
|
Beam size behind M2, posted by Ronic Chiche at Optical room about lasers and optics
|
Yesterday, we tried to better adapt positions of the telescope lenses, dynamically, during the lock, to improve the matching between input beam and cavity
mode.
it is a difficult task because it is quite sensitive to the alignment. we need to realign very often... and it is a long process. |