Deposit on S-box mirrors after return from LMA, posted by Loïc Amoudry at Optical room about lasers and optics 
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| Cleaning on dirty surface shows something is deposited on the surface. Cleaning displaces and removes part of the deposit. |
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Impacts on mirror's surface, posted by Loïc Amoudry at Optical room about lasers and optics
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All the mirrors show impacts on there surface (some of them do not show deposit). Does it come from experiments or fabrication ? Are these holes
or bumps ? |
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AFM performed on S-BOX mirrors, posted by Loïc Amoudry at Other about lasers and optics
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| 29/02/19 - AFM has shown that spots on mirror's surfaces are bumps and not holes. |
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Meeting with LMA people, AFM, posted by Loïc Amoudry at Other about lasers and optics
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30/01/19 - The following powerpoint shows the results discussed with LMA people.
What came out from the discussion is:
- Their cleaning method uses demineralized water drop on a spinner. It is probably the explanation of the circular traces on the mirror's |
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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; |
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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AFM+ InfraRed spectroscopy (IR spectro) has been performed, posted by Loïc Amoudry at Other about lasers and optics
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AFM+ InfraRed spectroscopy (IR spectro) has been performed on 400kW S-BOX mirrors.
Seems that XPS made M3 and M4 dirty, but M1 have also ome dust. M2 seems clean, further AFM experiment should show that it is as clean as M1. |
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Mirror's cleaning, posted by Loïc Amoudry at Optical room about lasers and optics
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XPS has been proceeded on the 400kW SBOX mirrors M3 and M4 (the initial cavity spherical mirrors) in frebruary 2019. Deposited a lot of particles on
these mirrors.
All the mirrors received a Infrared spectroscopy the 12th of november 2019. Deposited glue on the non-reflective face (was used to hold them). |
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Mirror's installed, posted by Loïc Amoudry at Optical room about lasers and optics
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| The initial 400kW SBOX mirrors which have been cleaned ont 28th of november have been installed this morning on the SBOX. |
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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 |
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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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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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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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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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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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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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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 |