Mightylaser Amplifier , posted by Manar Amer at Optical room about lasers and optics | cabling
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Migthylaser amplifier has been moved from the SBox table to the PLIC table.
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OEwaves CW Laser - Phase Noise , posted by Manar Amer at Optical room about lasers and optics | detectors and electronics 
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We started measuring the phase noise on the OEwaves CW laser.
Class 3b
wavelength 1.5 um
The
procedure is done using self coupling of the laser
splitter 50%-50%\
delay line 100 m
all fibers are PM type
(polarity maintained)
Photodetector is "lab buddy", very fast diode.
Note: différance from schematic (we did not |
OEwaves CW Laser - Phase Noise , posted by Manar Amer at Optical room about lasers and optics | detectors and electronics
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a correction on the wavelength of the laser it is 1030 um
Manar
Amer wrote:
We started measuring the phase noise on the OEwaves CW laser.
Class |
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OEwaves CW Laser - Phase Noise , posted by Manar Amer at Optical room about lasers and optics | detectors and electronics
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correction on unit 1030 nm
Manar
Amer wrote:
a correction on the wavelength of the laser it is 1030 um |
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Origami SN2440 133MHz laser tests, posted by Ronic Chiche at Optical room about lasers and optics
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Today, we received the Origami SN2440 133MHz oscillator from repair (NKT mentioned a defective wire inside the controller....)
We immediately installed it behind an isolator (Faraday rotator+PBS+halfwave plate).
the output power is around 60mW. |
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Origami SN2440 133MHz laser power measurment... and failure, posted by Ronic Chiche at Optical room about lasers and optics
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we received from NKT the Origami SN2440 133MHz oscillator from repair on 2020/12/17
and we measured the power trend from 2020/12/21 until the whole winter Hollyday, during 14 days and 17h (1 273 334 s).
the power was quite constant, about 58mW (the measurement has been done with the OD2 filter and using a (x20) factor in the software to compensate |
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Transmission Measurements for the Mirrors. , posted by Manar Amer at Optical room about lasers and optics 6x
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Thursday 10 December 2020: First Test Measurement - Inside Box
The transmission ( T ) for the mirrors of SBOX
and ThomX was measured over a range from the center of the mirror up to 5mm.
The first setup was initially done while the
mirrorr is installed inside the metal box, when measuring T we observe that there is an erregular change in the power measured as we move azay from |
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Mirror's cleaning and microscope imaging, posted by Loïc Amoudry at Optical room about lasers and optics 14x
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On 10th of december 2020 we cleaned the SBOX mirrors and took microscope images (the name of the images indicates what they are).
There are 7 mirror, the initial M1 (spot in the center), M2 (spot on the edge), M3 and M4 which made the 200-400kW and the M2, M3 and M4 SPARE.
The difference we make between M3 and M4 SPARE is the number on the box (11 or 13). |
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amplifier, posted by Huan Wang at Optical room about lasers and optics
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Onefive output power is 24mW now, and 2.41mW(after EOM) injected into fiber,
a injection power monitor added, 99% (2.06mW) injected into amplifier, 1% (16.1uW) monitored with photodiode DET36A/M, which
gives ~500mV DC signal on oscilloscope with 1Mohm impedanc; |
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amplifier, posted by Huan Wang at Optical room about lasers and optics
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I just had a phone call with Jérome and he told me 2 things :
* Be carefull ! the MightyLaser amplifier is not designed to work with 33MHz laser : the streching level is not sufficient !
One could worsen the phase noise by self-modulation due to peak power or even distroy the amplifier ! |
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Microscope and cleaning of SBOX mirrors, posted by Loïc Amoudry at Optical room about lasers and optics
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The mirrors went in the cavity the 28th of november (We did several power up to 30kW stored and only one to 40kW then the power went down to 2kW
during the run).
Microscope study shows that mirrors get some dust during the handling [travel from microscope to SBOX --> installation --> |
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Power up to 48kW crater effect again, posted by Loïc Amoudry at Optical room about lasers and optics
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As we said, after glow discharge and spin coater we recovered a low power finesse ~23000 (aligning away from the M1 crater).
Today, we have made some power up to 48kW (3A on 3rd stage). At this power, there was no important effect on the transmission which can be compared
with the coupling (see image "3A_136mWtrans"). We waited ~20min without aligning and the power dropped slowly (misalignment) to 39kW. |
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analysis of stored and reflected power, posted by Ronic Chiche at Optical room about lasers and optics 6x
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the 10th of January, we increased the power of the amplifier to study the cavity transmitted and reflected power signals.
analyzing the noise transfer functions of transmitted and reflected power one could deduce the Finesse of the cavity.
the power of this technic (if it is confirmed) does not depend on the decay time of one signal which depends on the speed of the cut off but on |
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analysis of stored and reflected power, posted by Ronic Chiche at Optical room about lasers and optics
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A chart which summarizes the data we have or we can estimate.
in orange, the case 1, where we suppose the initial cold Finesse is the one measured by modulation technique in December 2019 (F=20.8k). |
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analysis of stored and reflected power, posted by Ronic Chiche at Optical room about lasers and optics
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with this Finesse around 22-23k, the technique comparing TRANSMISSION and REFLECTION signals doesn't work, even in taking into account individual
photodiode time responses.
It seems that the cavity is not completely stationnary and the shapes are not comparable easily with just a Low Pass Filter related to the Finesse. |
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SBOX mirrors cleaned, posted by Loïc Amoudry at Optical room about lasers and optics
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Today, SBOX mirrors have been cleaned with spin coater on HR face and isoprop on back face. They show similar spots as before.
They also have been installed in the SBOX. The M1 mount has been displaced so the beam doesn't go in its center (spot). |
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SBOX mirrors cleaned, posted by Loïc Amoudry at Optical room about lasers and optics
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Yesterday, after installation and alignment of mirrors and cavity, the Finesse has been measured with cavity at air pressure, with Koheras and modulation
technique.
the measurement has been done 7 times with quite different fits for the Finesse : 21.5k, 21.5k, 23.7k, 21.3k, 22.3k, 22k, 21.5k |
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SBOX mirrors cleaned, posted by Loïc Amoudry at Optical room about lasers and optics
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Today we put the cavity to vacuum (~ 0.1 mBar) and we measured again the Finesse with Koheras and modulation technique.
the measurement has been done 3 times with Finesse of 23.2k, 23.8k, 23k
Loïc |
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Glow discharge cleaner on SBOX mirrors, posted by Loïc Amoudry at Optical room about lasers and optics
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The glow discharge cleaner has been tested on the SBOX mirrors.
I've put them 1 by 1. Each run was 15min long at 15mA. The mirrors HR face was always away from the electrode and ~35° angle
with the support. These values have been choosen thanks to the reference: |
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CFBG removed from ThomX CELIA amplifier, posted by Loïc Amoudry at Optical room about lasers and optics
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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). |
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AFM analysis of M2, posted by Loïc Amoudry at Optical room about lasers and optics
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We had enough time to proceed a quick scan of M2 which has also a hole but not centered on the mirror.
The hole is larger and higher than the one on M1. But the vertical range was to high for the AFM. Then we cannot see if there are sparkles or
not on this image. Further study with microscope would be welcome. |
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AFM analysis of M1, posted by Loïc Amoudry at Optical room about lasers and optics
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AFM has been proceeded on M1 and M2.
The pdf shows the first images taken with the PLIC room Leica microscope (zoom x10 and x80).
Then the hole has been studied with a handmade microscope. It brought a better resolution. We can now see the hole has an edge, a center structure |
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Cavity beam axis moving with power, posted by Ronic Chiche at Optical room about lasers and optics 9x
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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 |
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Beam size behind M2, posted by Ronic Chiche at Optical room about lasers and optics
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Beam diameter behind M2 :
- 2nd stage @ 6A - 1kW inside cavity
sx = 2120 µm |
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Beam size behind M2, posted by Ronic Chiche at Optical room about lasers and optics
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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. |
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Beam size behind M2, posted by Ronic Chiche at Optical room about lasers and optics
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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. |
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Optical amplifier polarization state, posted by Ronic Chiche at Optical room about lasers and optics
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We placed a PBS + 2 photodiodes (PhD1, PhD2) at the output of the amplifier to check how the polarization of the amplifier changes with power.
example with 2nd stage @ 6A :
PhD1 = 24.7 mV |
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Optical amplifier polarization state, posted by Ronic Chiche at Optical room about lasers and optics
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The polarimeter was giving a strange 50% of DOP of the light coming from the cavity.
we had to calibrate (LONG calibration process with care) the polarimeter to get a proper 100% of DOP !
the polarimeter needs also a good alignment with 2 mirrors, a colimated beam and a max power on photodiode between 0.7 and 0.8 (use electronic gain |
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Optical amplifier polarization state, posted by Ronic Chiche at Optical room about lasers and optics
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polarization state of the cavity at higher power : 20kW, 30kW and 33kW (slight CEP and alignment optimization) :
the polarization state changes only a little to ~ 87° and is almost linear.
Ronic |
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first data with 3A on the 3rd stage, posted by Ronic Chiche at Optical room about lasers and optics
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Today, at 3A on the 3rd stage, we saw some HOM effects.
the transmissions is about 100mW which corresponds to 30kW inside cavity.
we tried to play with D shape motors but without success. |
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first data with 3A on the 3rd stage, posted by Ronic Chiche at Optical room about lasers and optics
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2 pictures :
typical beam with HOM
typical beam after moving the D-shape motor : no more HOM |
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2nd stage amplifier issue, posted by Ronic Chiche at Optical room about lasers and optics
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the 2nd stage amplifier needed several hours (4-5h) to reach its nominal power (we look at photodiode level on a scope), instead of the awaited 30 minutes.
could it come from the probable spectrum shifting of the OneFive laser ?
(the power coming from the CVBG, coupled to the fiber, is lower than expected). |
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2nd stage amplifier issue, posted by Ronic Chiche at Optical room about lasers and optics
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Last time, we switched ON directly the 2nd stage at 6A without increasing/decrinsing slowly the current.
today, we switched ON the chiller, switched ON the 1st stage, switch ON the power supply of the 2nd stage at 0A and then we increased slowly the
current until 6A... and the problem disappeared. |
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2nd stage amplifier issue, posted by Ronic Chiche at Optical room about lasers and optics
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2nd stage output power was going down. We checked the pump diode technical data sheet and the operating temperature is [25°C:35°C].
We increased the chiller temperature setpoint from 19°C to 23°C.
Then the output power increased (93mW on 2nd stage photodiode). |
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FSR and Finesse measurement, posted by Ronic Chiche at Optical room about lasers and optics
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Yesterday the cavity has been aligned and locked with the CW Koheras laser.
the FSR has been measured by modulation technique at 133.344MHz at 1mbar pressure in the cavity.
the polarization has to be optimized for the Finesse measurement otherwise, some "shoulders" appear beside the Airy peak and reduce |