M4 motor using icepap controller and jive/Atkpanel IHM, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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Kevin moved the M4 mirror controller from the ISP controller to some ICEPAP controller.
the IHM to access this ICEPAP controller is accessible by launching 'jive' from any account ('operateur.thomx' for example).
once in the jive window, one has to select the 'device' tab, then select the OC=>OP=>OCH.02-MOT.03 device. |
M4 motor using icepap controller and jive/Atkpanel IHM, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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one problem is the FP-cavity/laser lock loss when one moves a FP-cavity motor.
with acceleration = 0.01 units/s² and velocity = 50mm/s (here, the 'mm' unit seems strange as it is very fast), it's enough
to make a move fast enough for small displacements (10 steps for example to center PZT position) and it seems that the cavity stays locked (only the FP-cavity/laser |
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Long term lock of Laser-FP cavity-RF reference, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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today for the first time, we were able to make a long term lock of all the elements (Laser on FP cavity and FP-cavity on RF reference) during 20
minutes @50kW without any single loss of lock.
the success of this long term lock was coming from the possibility to drive the Smaract motor in piezo-scan mode and to apply a heating on one |
Long term lock of Laser-FP cavity-RF reference, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics 
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today, I did a 20 minutes "double lock" run w/o any single lock loss.
the attached file shows the recorded RMS beating voltage between 500MHz signals (laser harmonic and RF reference).
the end of the plot after iteration ~1.8k shows the lock loss to the RF reference. |
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Long term lock of Laser-FP cavity-RF reference, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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this afternoon, we did a new long-term "double lock" run w/o any single lock loss during 1/2h.
we did 2 acquisitions :
fig 1 : phase measurement between the 33MHz signal coming from the laser and the 500MHz RF. |
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Laser cavity temperature/pressure sensitivity, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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laser cavity :
when one decreases the laser motor position, the laser repetition rate increases (laser cavity length decreases).
=> +/- laser motor step => +/- laser cavity roundtrip length => -/+ |
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Laser cavity temperature/pressure sensitivity, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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Now, I placed a temperature probe stuck on the laser housing itself.
fig. 1
one can compare the temperature measured at the surface of the laser housing and the beating frequency with the 500MHz reference oscillator |
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Laser cavity temperature/pressure sensitivity, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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the last thing we did with Daniele, is to start/stop the airflow on top of the housing (closed) to see a possible pressure effect on the laser frequency
drift.
fig 1 : in green, the temperature measured with the probe stuck on the laser housing. |
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Laser cavity temperature/pressure sensitivity, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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today, I swapped the 500MHz RF reference oscillator for a Siglent 500MHz DDS oscillator.
see the attached plot : the beating frequency with the 500MHz laser harmonics produces the same behavior as before.
so, the oscillations should come from the laser temperature regulation. |
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Laser cavity temperature/pressure sensitivity, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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long-term correlation, over 5-6 days, between the temperature measured in the bunker, outside of the housing (blue curve) and the temperature measured
with a probe stuck on the laser housing, inside of the FP-cavity housing (green).
it's a perfect correlation with almost the same temperature scale : 1°C outisde the housing => 1°C of laser housing |
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Laser cavity temperature/pressure sensitivity, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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this morning, I did a 500MHz beating frequency (Laser vs RF) drift test with the Smaract motors configured with "Sensor Mode" OFF over 50 minutes
(~ 1500 acquisitions)
compared with previous measurements, one observes a much more smooth "exponential-like" drift compared to "Sensor Mode" ON |
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Laser and FP cavities frequency adjustment, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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at the beginning of the procedure, the frequency gap between the new Ring 33MHz frequency (33.3378MHz) and the laser/FP cavities frequency was 12.33kHz
=> the Smaract motor position was at +100µm
=> the FP cavity motor Mot.03 position was at -358 720 steps |
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Laser and FP cavities frequency adjustment, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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This afternoon, I did the 2nd half of the travel: dF @ 33MHz = 0Hz
=> the Smaract motor position is now at +1750µm
=> the FP cavity motor Mot.03 position stayed at -200 000 steps |
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Laser FP operation, posted by Daniele Nutarelli at Optical room about lasers and optics
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This morning FP Laser was operating well locked at 30 KWatts in stable vay.
There are some fluctuations due tu pointing instabilities probably dues to temperature fluctuations in de bunker.
In the attacced picture are reported the lock parameters and signals. |
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Laser Amplifier used at 70%, posted by Ronic Chiche at ThomX igloo about lasers and optics
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today, I installed a laser dump just before the telescope to avoid any high power (50W instead of 17W usually) issue in the injection line.
last time, we saw some plastic mounts of the polarizers slightly burnt because of some small misalignment.
I used a thorlabs LB2 (see picture) which is able to manage 80W CW or 25J/cm2 pulses => this is OK in both cases : 50W CW / 1.5µJ/pulse |
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Laser / FP-cavity "day by day" locking, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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today, we locked the FP cavity at ~50kW with 30% laser amplifier ratio (16W) during almost all the day (from 10am to 4pm)
CEP optimized for MCS-1/Ch2 = -244µm at the end of the day.
once one finds the proper CEP value to reach to correct loops gain, the cavity lock and power are very stable: |
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Laser / FP-cavity "day by day" locking, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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as the temperature is back to a normal value ~ 20.8°C, the injected power to the amplifier (PD_IN in the Alphanov software) is back to 3.15mW without
doing any alignment.
this morning the lock was around 48.5kW with 30% laser amplifier ratio (16W) after CEP/alignment tuning. |
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Laser / FP-cavity "day by day" locking, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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temperature since we moved to temperature probe (jump at the beginning of the plot) below the ring on a metallic base.
Ronic
Chiche wrote:
as the temperature is back to a normal value ~ 20.8°C, the injected |
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Laser / FP-cavity "day by day" locking, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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temperature @ 22.3°C
today, all the PC applications were closed except the web browser.
I had to restart all of them, then try to relock. |
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Laser / FP-cavity "day by day" locking, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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temperature @ 21.9°C
48.5kW inside CFP for 30% amplifier ratio
Frep Laser motor = 123.4µm |