Temperature control of the Laser length with the inside Peltier, posted by Ronic Chiche at ThomX igloo about lasers and optics
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bunker temperature @ 22.5°C
today, Sebastien Pitrel improved its python software to manually control the laser peltier. |
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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: |
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. |
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 |
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bunker temperature curve, posted by Ronic Chiche at ThomX igloo about detectors and electronics
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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. |
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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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Ring frequency / Laser "day by day" locking, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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| today, the equivalent Smaract position corresponding to the 500.25MHz ring frequency is +156µm on MCS-1/ch0 (closed loop mode) |
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Ring frequency / Laser "day by day" locking, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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temperature stable around 20.8°C
today, the equivalent Smaract position corresponding to the 500.25MHz ring frequency is +158.4µm on MCS-1/ch0 (closed loop mode)
it is very difficult to maintain both loops in the same time as soon as it is needed to move one motor (CFP or Laser) because of the one element |
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Ring frequency / Laser "day by day" locking, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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temperature stable around 21.7°C
today, the equivalent Smaract position corresponding to the 500.25MHz ring frequency is +147µm on MCS-1/ch0 (closed loop mode)
Ronic |
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some changes in the feedback scheme, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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from several weeks, the maximum power stored in the FP-cavity was ~ 5kW.
today with Daniele, we finished to investigate the problem, and now the power inside the FP-cavity is back
to ~50kW for 30% of laser amplifier ratio (~16W). |
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!!! strange amplifier beam pointing fluctuations !!!, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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this morning, I locked the cavity to ~25kW without any problem.
but this afternoon, the reflected power exhibited low frequency (~1Hz) fluctuations of about 10% without any lock.
the reflected PhD is a DET10 which has a small surface. |
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!!! strange amplifier beam pointing fluctuations !!!, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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we confirmed the effect of the bunker temperature on the laser amplifier "beam pointing" fluctuations.
once the temperature is getting back to stable values, it doesn't happend again.
we bought a temperature data logguer to monitor them in the future: https://www.picotech.com/data-logger/tc-08/thermocouple-data-logger |
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Tests of pointing stability of the laser CFP, posted by Daniele Nutarelli at ThomX igloo about lasers and optics
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Last monday with Victor we have cheked the stability of de pointing of the laser FP.
The climatisation was operating since 3 days in satble way. The laser pointing was very stable before to inejct in to the cavity (picture 1)
and also for the reflexion from the cavity (picture 2). |
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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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Fast feedback loop between laser and FP cavity, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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today, we tried to lock the FP cavity with the Smaract motors ON (with option -LV).
we know the Smaract controllers produce some noise and the lock is very bad or impossible when the controller in ON (whatever the displacement mode
is : closed or open loop, or piezo scan). |
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Fast feedback loop between laser and FP cavity, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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today, after the several unsuccessful attempt yesterday to get an improvement in the lock,
we decided to "rebuild" the error signal electronics block by block and step by step :
the scheme is basically : |
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Fast feedback loop between laser and FP cavity, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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this afternoon, we tried to better understand how to drive properly the EOM to kill high frequency noise.
we locked to laser on the FP-cavity as usual.
then we injected a 0-10V square signal on the laser EOM @ 1KHz (with fast rise and fall times ~ 10ns) |
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Fast feedback loop between laser and FP cavity, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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I copy the post about Fast Feedback loop : https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/265
This morning,
- I installed the fast feedback loop. |
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!!! strange FP cavity behavior => impossible to lock !!!, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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suddenly, BEFORE switching the HV amplifier ON and BEFORE connecting it to the EOM (in order to explore the HV effect on the EOM for the fast feedback
loop),
we lost the lock between the laser and the FP-cavity: in attchement a plot a the lock with the "best" PID parameters. |
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!!! strange FP cavity behavior => impossible to lock !!!, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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this morning, we tried:
- to move a bit the arm of the L-shape off the beam axis (in case of it could have touch something and induce vibrations) => no effect
- to change the CEP to get an equivalent lower Finesse => weak improvement |
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!!! strange FP cavity behavior => impossible to lock !!!, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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it could be also an optical unstability, as when the intra-cavity power increases, the radius of curvatures of the mirrors increases too due to thermal
effect, and then one could go in the instability region.
but if it was the case, by reducing the power in the FP-cavity, we would also reduce the thermal effect and then, we would come back in the stability |
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!!! strange FP cavity behavior => impossible to lock !!!, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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This morning,
- I installed the fast feedback loop.
now, the error signal goes to the Laselock AND |
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!!! strange FP cavity behavior => impossible to lock !!!, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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this afternoon, in adjusting the CEP and improving the parameters of the lock, I was able to get ~ 47kW stable inside the cavity, always for 30% of laser
amplification ratio.
it confirms that the Finesse, and then the gain of FP-cavity, has suddenly increased thanks to some "mirrors surface cleaning" |
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drift calculation for the SMA100A, posted by Ronic Chiche at ThomX igloo about lasers and optics
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the goal is to estimate what could be the frequency drift at 500MHz for the SMA100A: see phase noise datasheet in attachement
Sphi(f) = FFT ( Rphi(T) ) = FFT ( < Phi(t) Phi(t+T) > )
at low frequency, Sphi(f) ~ A / (f^n) = A*(2pi)^n / (i2pi*f)^n => Rphi(T) = A*(2pi)^n*T^(n-1) / (n-1)! |
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work with HV voltage on the Laselock, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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presently, the voltage on the laser PZT is 0-10V, but during the several runs we did, this voltage is too low to compensate low frequency fluctuations:
we need to change often the motors position implying a cavity lock loss.
we have to check if running the laser PZT with the HV output of the Laselock is possible without too much additionnal noise. |
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work with HV voltage on the Laselock, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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Yesterday, I checked the 2 output HV channels of the LaseLock : they work properly but the noise is bigger than the low voltage outputs
~ 1mV rms on 0-10V outputs
~ 8 mv rms on 0-100V output |
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work with HV voltage on the Laselock, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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This afternoon, I connected the HV output of the Laselock (instead of the standard 0-10V output) to the FP-cavity PZT to increase the locking range.
I didn't see any degradation of the FP-cavity/synthesizer lock.
Ronic |
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Removing high order modes, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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this morning we locked the laser and the FP-cavity with ~ 40kW => some HOM appeared "randomly" depending on the power.
we tried to play manually on the L-shape arm :
- first, we moved horizontally to put the L-shape in the beam axis |
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Removing high order modes, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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here is the picture of the L-shape arm and the inside of the vessel.
this image corresponds to the "zero" position on each positionner.
Ronic |
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Removing high order modes, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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yesterday with Daniele, we tried again to move the arm horizontally and vertically from the "zero position" to have a better understanding
of the beahvior,
but it is roughly the same : |
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33MHz oscillator + Alphanov amplifier lock, posted by Ronic Chiche at ThomX igloo about lasers and optics
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the last tries to lock the 33MHz + amplifier to the 30k Finesse FP-cavity were unsuccessful.
during a laser Frep scan using the Laselock, one observes that the main cavity resonance is not able to stay inside the PZT scan range from one
scan to another (500ms-1s period) |
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33MHz oscillator + Alphanov amplifier lock, posted by Ronic Chiche at ThomX igloo about lasers and optics
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finding the right modulation/demodulation PDH phase is very difficult on the main resonance because the we get non stationnary signals with a lot of
oscillations.
changing the phase, in this condition, does not really change the error signal. |
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33MHz oscillator + Alphanov amplifier lock, posted by Ronic Chiche at ThomX igloo about lasers and optics
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today with Daniele, we locked easily (but with a noisy lock) on the secundary resonance and we tried to lock on the main resonance (with very low coupling
~10% which mean a CEP ~Pi)
the lock was possible but was very noisy. |
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33MHz oscillator + Alphanov amplifier lock, posted by Ronic Chiche at ThomX igloo about lasers and optics
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After removing the 2 generators from the optical table, the lock is much more stable and now, it is possible to lock on the main resonance with a poor
CEP but with quite good stability.
the coupling is still very low ~ 5% for that CEP but if one improves it (CEP ->0), using the laser double-wedge motor, one clearly sees an improvement |
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33MHz oscillator + Alphanov amplifier lock, posted by Ronic Chiche at ThomX igloo about lasers and optics
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this morning, I tested the laser+amplifier @ 30% lock on the FP cavity with and without Smaract motors.
I recorded the PDH error signal during a lock:
- blue : with Smaract motors controller powered ON but motors are stopped |
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33MHz oscillator + Alphanov amplifier lock, posted by Ronic Chiche at ThomX igloo about lasers and optics
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I checked with the Matlab code below the CEP detuning effect (2nm sech² spectrum... not exactly the same as in ThomX)
@ CEP = 0 => coupling = 100% and Gcav = 10.5k
if all the coupling loss comes from the CEP detuning effect : |
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33MHz oscillator + Alphanov amplifier lock, posted by Ronic Chiche at ThomX igloo about lasers and optics
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we checked yesterday morning the real input power @ 30% for the amp => it is 16W in agreement with the previously measured values
Ronic
Chiche wrote:
I checked with the Matlab code below the CEP detuning effect (2nm |
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33MHz oscillator + Alphanov amplifier lock, posted by Ronic Chiche at ThomX igloo about lasers and optics
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Today, we locked the cavity with input power @ 30% for the amp => we got 40kW with only 30% of coupling (and a bad lock => we could have more power
inside cavity).
P@30% = 16W |
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33MHz oscillator + Alphanov amplifier lock, posted by Ronic Chiche at ThomX igloo about lasers and optics
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redoing the PDH error signal scheme with discrete components is more flexible and it is easier to check the signal/noise ratio.
now, we are able to get a quite clean lock only with the PZT correction (w/o fast feedback correction using the EOM) even with both motors controllers
ON (cavity and laser). |
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Onefive laser modelock and Smaract CEP controller, posted by Ronic Chiche at ThomX igloo about lasers and optics
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today, during an attempt in improving the CEP with the Smaract controller CH2, we lost the laser modelock.
at this point, we decided to reference the Smaract CH2 for CEP :
now, 0 mm is roughly the middle of the motor range. |
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Smaract controller remplacement, posted by Ronic Chiche at ThomX igloo about lasers and optics
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previously, we were using a spare Smaract MCS controller to drive the Onefive linear stages (without -LV -low vibration- option and
using Ethernet),
during the repair of the initial MCS controller with -LV option. |
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FP-cavity FSR shift, posted by Ronic Chiche at ThomX igloo about lasers and optics
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today, to match the ring frequency at 500.25MHz (15th laser harmonic), we did a frequency shift on the laser using the Smaract motors (not too fast,
~2µm/s, to prevent laser modelock loss)
and we "followed" this shift on the FP-cavity using the FP-cavity motors. |
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Equipments shutdown, posted by Ronic Chiche at ThomX igloo about lasers and optics
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on the August 30rd and 31th, a global power shutdown was forseen for ThomX.
to prevent damage on equipments, I switched off all of them (and disconnected power cables from the wall plugs).
yesterday, after the week-end, all the equipments have been restarted and the cavity as been locked properly. |
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ThomX ring injection kicker noise => USB communication issue with Alphanov amplifier, posted by Ronic Chiche at ThomX igloo about detectors and electronics
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several times already, when the electrons ring injection kicker is running @10Hz, we observed peaks at the same frequency on reflected and transmitted
photodiodes,
at the exact moment when the kicker is activated. we have in addition, USB communication issues with the Alphanov amplifier... the connection is |