ELOG THOMX commissioning

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 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 :
@ CEP = pi/5 => coupling = 20% and Gcav = 2.14k (~ 10.5k x 20%)
so, it does not matter if the coupling loss comes from the CEP detuning effect or from beam mismatch or misalignment.

=> we should have more power at 20% coupling, not 10kW but 35kW !!!
=> we have to check the real input power !

Ronic Chiche wrote:

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
- yellow: with Smaract motors controller powered OFF

with Smaract motors controller powered ON and motors stopped, one can see a group of resonances around 10kHz (8 - 11 - 14kHz) which disappears when the controller is powered OFF.
one can see also a group of resonances around 25-30kHz for which some peaks desappear when the controller is OFF but most of them are still there... could it come from noise on the Onefive laser PZT ?
one can see also a noise reduction at low frequency with a corner frequency around 17kHz, which could be the Unity Gain Bandwidth of the feedback loop on the laser PZT (fast feedback loop on EOM was disconnected)
=> to be confirmed

*************************************************************************************************************************************************************

I was able to lock with a decent noise on transmission and reflection signals @ Pin=17W (30%) of input power and with a coupling ~ 20%.
I measured 31mW in transmission => Pcav ~ 10.3kW (T ~ 3ppm)
as T1=115 ppm and F=30000, the cavity gain is T1*(F/pi)^2 = 10.5k,
so, the FP cavity power should have been 17W * 20% * 10,5k = 35.7 kW !!! (maybe the formula is wrong if the coupling loss comes from the CEP detuning effect)
=> we have to check the incoming power and the formula !

so, maximum expected power in FP-cavity could be 70W * 100% * 10,5k * (10.3/35.7) = 210 kW !!! :-(

*************************************************************************************************************************************************************

I was able to redo the lock easily in remote in the control room (with the Smaract motors controller OFF).

Ronic Chiche wrote:

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 of the coupling... but at the cost of the lock stability.

the reason of the poor coupling is also because the laser amplifier is used at 0%, for which we know the part of the laser signal power, compared to the total power, is low.
(a part of the beam @1030nm is not propagating in the fiber core of the amp, and then, it cannot be coupled to the FP-cavity).

the fast lock loop on the EOM has been disabled for the moment.
it has to be installed back to improve the stability at a better CEP.

at present, the FP-cavity power is estimated at ~ 90W (~270µW in transmission of ~3ppm mirrors) for ~300mW of total power coming from the laser amp.

next steps :
- in Open Loop : check what is the best coupling we can observe for CEP=0 @ P ~ 10W (laser amp at ~ 25%)
- in Closed Loop : @ P ~ 10W => measure the best transmitted power after alignement/polarization/feedback adjust => ~ 3-10kW in the cavity ?

Ronic Chiche wrote:

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.

I installed a fast loop using my small DC amplifier based on OP37 (max gain=100) modified to be AC coupled to avoid to amplify the PDH box offset.
the output votage swing of the OP37 is only ~10V. Thus, the effect of this fast loop on the lock stability is not visible !

Thus, I added the M250 Leysop HV amplifier (see attached documentation), which is able to drive an EOM with >5MHz bandwidth and ~250V swing, after my OP37 amplifier.
with this additionnal HV amplifier, now we can clearly see the effect of the EOM loop which improves the lock stability BUT, even with a poor CEP, the lock is very unstable on the main resonance.
it seems the optical phase noise is still too large and/or its BW too high to be completely compensated.

The next step is to try to remove all the possible noise sources from the optical table:
- the laptop placed on the ionic pump
- the 2 Rigol generators on the table surface
and switch off the controller of the Smaract laser cavity motors.

If it doesn't help, we can send the error signal to a spectrum analyzer to have a better view of the different harmonics involved in the residual phase noise.
could it remain some noise above the present PDH box BW (1.9MHz LP filter) ?

lastely, we can also make an optical phase noise measurement to check if the Alphanov amplifier does not add some noise.

Ronic Chiche wrote:

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.
Then, we moved on the first secundary resonance with less gain and less coupling.
Thus, the error signal is more similar to the theoretical PDH signal => one can adjust the modulation/demodulation PDH phase to get the maximum error signal.

then, we locked pretty easily on this first secondary resonance, with a coupling around some % when we adjust the CEP motor.

we tried to lock on the main resonance but it is too noisy and unstable.
it seems we really need high BW feedback.

I tried to add a fast analog loop on the laser intra-cavity EOM but without a clear effect.
the problem is the gain of this loop : it is difficult to produce a "high voltage" (above 10Vpp) on this EOM.
I put "my" amplifier but the voltage output is limited... commercial amplifiers will have the same issue.
we can add HV amplifiers but it takes place and it will add some noise on the signal.

A loop with an AOM could be easier to install and manage... but at the price of a loss of power before the laser amplifier...

Ronic Chiche wrote:

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)
is it the effect of a large and slow phase noise ?

some informations:

- The 33MHz laser came back at lab from repair on March 2018.
- it has been sent to Alphanov in May 2020.
- it failled and has been sent to NKT/OneFive for repair in September 2021
- it came back to lab from repair in June 2022.
- on post #92 (Feb. 2020), it seems that we already locked the 33MHz laser + CELIA amplifier to the ThomX FP-cavity.

- The PZT sensitivity for the 33MHz laser is given to 0,3Hz/V for Frep <=> 2.6MHz/V for optical frequency.
=> 10V on PZT is equivalent to 26MHz of optical frequency shift which is less than FSR !

- by comparison, the PZT sensitivity for the 133MHz laser is given to 3.9Hz/V for Frep <=> 8.5MHz/V for optical frequency.

- by comparison, the PZT sensitivity for the NKT CW laser is given 10pm/100V for Wavelength <=> 30MHz/V for optical frequency

- by comparison, the PZT sensitivity for the ThomX FP cavity (Z20H38x40C) is 4nm/V for length expansion => 8nm/V for round-trip expansion <=> 0.03Hz/V for FSR expansion <=> 260kHz/V for optical frequency !!!
the PZT expansion estimation is in attached file.

223

Tue Jun 20 19:08:17 2023

=> we should have more power at 20% coupling, not 10kW but 35kW !!!
=> we have to check the real input power !

Ronic Chiche wrote:

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
- yellow: with Smaract motors controller powered OFF

*************************************************************************************************************************************************************

so, maximum expected power in FP-cavity could be 70W * 100% * 10,5k * (10.3/35.7) = 210 kW !!! :-(

*************************************************************************************************************************************************************

I was able to redo the lock easily in remote in the control room (with the Smaract motors controller OFF).

Ronic Chiche wrote:

the fast lock loop on the EOM has been disabled for the moment.
it has to be installed back to improve the stability at a better CEP.

at present, the FP-cavity power is estimated at ~ 90W (~270µW in transmission of ~3ppm mirrors) for ~300mW of total power coming from the laser amp.

Ronic Chiche wrote:

lastely, we can also make an optical phase noise measurement to check if the Alphanov amplifier does not add some noise.

Ronic Chiche wrote:

then, we locked pretty easily on this first secondary resonance, with a coupling around some % when we adjust the CEP motor.

we tried to lock on the main resonance but it is too noisy and unstable.
it seems we really need high BW feedback.

A loop with an AOM could be easier to install and manage... but at the price of a loss of power before the laser amplifier...

Ronic Chiche wrote:

the last tries to lock the 33MHz + amplifier to the 30k Finesse FP-cavity were unsuccessful.

some informations:

- by comparison, the PZT sensitivity for the 133MHz laser is given to 3.9Hz/V for Frep <=> 8.5MHz/V for optical frequency.

- by comparison, the PZT sensitivity for the NKT CW laser is given 10pm/100V for Wavelength <=> 30MHz/V for optical frequency

Attachment 1: ThomX_FP_intracavity_signal.m

clear
clc

% resonance order
% Main resonance => Nr=0
Nr=00;

c=3e8;
lambda0=1030e-9;
dlambda0=2e-9;

FSR=33e6;
T1=115e-6;
F=30e3;
CEP=2*pi/10;

L0=c/FSR;
f0=c/lambda0;
df0=f0*dlambda0/lambda0;
n0=round(f0/FSR);
dn0=round(df0/FSR);
n=n0-3*dn0:n0+3*dn0;

fcav=n*FSR;

Pin=sech(1.77*(fcav-f0)/df0).^2;
Ein=sqrt(Pin);

figure(1)
clf
plot(c./fcav*1e9,Pin)
grid on
xlabel('wavelength (nm)')
ylabel('power (A.U.)')
title('normalized laser power spectrum')

df_FSR=linspace(-FSR/2,FSR/2,1e6);
Ec=Ffp(df_FSR,FSR,T1,F,1);

figure(2)
clf
plot(F*df_FSR/FSR,abs(Ec).^2,'r')
grid on
xlim([-5 5])
xlabel('normalized frequency (Hz / LW)')
ylabel('real part (A.U.)')
title('FP-cavity intra-cavity power gain')

dLmax=lambda0/1000;
Nk=1e2;
dL=linspace(-dLmax/2,dLmax/2,Nk+1)-L0*CEP/(2*pi)*FSR/f0;
for k=1:length(dL)
    df=FSR*(dL(k)+Nr*lambda0)/L0;
    Frep=FSR+df;
    flas=(n+CEP/2/pi)*Frep;
    
    [Ec,Er]=Ffp(flas,FSR,T1,F,Ein);
    Gc(k)=sum(abs(Ec).^2)/sum(Pin);
    Gr(k)=sum(abs(Er).^2)/sum(Pin);
end

figure(3)
clf
plot(dL/1e-6,Gc,'.')
grid on
xlabel('length scan (µm)')
ylabel('cavity power gain (A.U.)')

figure(4)
clf
plot(dL/1e-6,Gr,'.')
grid on
xlabel('length scan (µm)')
ylabel('cavity refleced power gain (A.U.)')

% cavity field & reflectivity of the FP cavity
function [Ec,Er] = Ffp(df,FSR,T1,F,Ein)
rho=1-pi/F;
t1=sqrt(T1);
r1=sqrt(1-t1^2);
r2=rho/r1;
if r2>1
    error('r2 > 1 !!!!')
end
Fc=1i*t1./(1-rho*exp(-1i*2*pi*df/FSR));
Ec=Fc.*Ein;
Fr=r1+1i*t1*r2*exp(-1i*2*pi*df/FSR).*Fc;
Er=Fr.*Ein;
end

222

Tue Jun 20 18:45:10 2023

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
- yellow: with Smaract motors controller powered OFF

*************************************************************************************************************************************************************

so, maximum expected power in FP-cavity could be 70W * 100% * 10,5k * (10.3/35.7) = 210 kW !!! :-(

*************************************************************************************************************************************************************

I was able to redo the lock easily in remote in the control room (with the Smaract motors controller OFF).

Ronic Chiche wrote:

the fast lock loop on the EOM has been disabled for the moment.
it has to be installed back to improve the stability at a better CEP.

at present, the FP-cavity power is estimated at ~ 90W (~270µW in transmission of ~3ppm mirrors) for ~300mW of total power coming from the laser amp.

Ronic Chiche wrote:

lastely, we can also make an optical phase noise measurement to check if the Alphanov amplifier does not add some noise.

Ronic Chiche wrote:

then, we locked pretty easily on this first secondary resonance, with a coupling around some % when we adjust the CEP motor.

we tried to lock on the main resonance but it is too noisy and unstable.
it seems we really need high BW feedback.

A loop with an AOM could be easier to install and manage... but at the price of a loss of power before the laser amplifier...

Ronic Chiche wrote:

the last tries to lock the 33MHz + amplifier to the 30k Finesse FP-cavity were unsuccessful.

some informations:

- by comparison, the PZT sensitivity for the 133MHz laser is given to 3.9Hz/V for Frep <=> 8.5MHz/V for optical frequency.

- by comparison, the PZT sensitivity for the NKT CW laser is given 10pm/100V for Wavelength <=> 30MHz/V for optical frequency

Attachment 1: PDH_error_signal_with_Smaract_motors_ON-OFF.jpg

Attachment 2: Lock_at_amp_@30%.jpg

Attachment 3: 10kW_in_remote.jpg

221

Mon Jun 19 16:08:15 2023

lasers and optics | detectors and electronics | cabling | software

The computer is possible to connect from the control room,

we are able to run remotely the amplifier, cavity motors, oscillator motors, lase lock (note: there is an issue with the keyboard, we are not able to use it with remote access!!!!!!!!)

Note on Amplifier: On Friday, Daniele and Ronic faced again the temperature issue that came up before. it is due to the fluctuation of the diode temperature.

It was fixed today by Ronic and Daniele. it seems there are three diodes for monitoring the temperature, only one was connected, and it had issues, with some directions from alphanov.

Ronic just removed the defective diode and soldered (connected) a different one. The amplifier should work without this issue.

now we start searching for X-rays after locking the cavity remotely

Manar Amer wrote:

In the morning, we locked on the first resonance. With an increase on the amplifier power @ 20-25% and 30%, which reduced the noise

we manage to get a coupling when improving the CEP up to 55 - 60 % coupling : put there is still a drift on the CEP

The controller for the oscillator frep and CEP produces a lot of noise, even if it is disconnected. we need to switch it off to remove its effect (Kevin will order a new one)

The image attached is of the oscilloscope lock on the first resonance @30% amplifier power ~ 10 W injected into cavity,

transmitted power ~ 36 mW (cavity average power 12 kW)

cavity effective gain > 1200

in the afternoon, we installed and aligned a gentec power meter we can monitor from the computer. (will need to buy a permeant one for ThomX)

there was an issue with the laselock USB connection, yet to be solved.

and the control of the computer.

Manar Amer wrote:

Today with Ronic,

starting with major events that happened (Water circulation + ThomX valves )

Early in the morning a company worked on the water network, it seemed it was not restarted properly so there was no water circulation in the main ThomX pipes.
- There was an error on the ThomX amplifier chiller , which was noticed at the end of the morning work , where we couldn't find the cavity resonance , could be due to the temperature increase of the amplifer.
- Solved : the issue was solved by restarting the water network and the amplifier chiller was restarted an no error found and temp. Stabilized around 25°
Around 12h15 ThomX there was a power cut off for less than a second (micro cutt), which cased all the valves to close, the valve air compressor did not restart after the power cut off, we restarted it with Daniele in the evening with the help of Marie and the valves open around 5-6 bar , you will see then all the controllers green and the valves will open.

Results of the day :

All the power supplies and function generators are under the table, nothing on the table (reduced noise on the signal)
EOM of Oscillator Off (for now, might turn on if needed)
Amplifier on 0% , output ~ 300 mW
Locked on the first resonance of the cavity, lase lock parameters to be optimized better
Transmitted power increased to ~ 267.2 uW
Average power inside cavity = 89. 06 W , peak power = 0.2 kW (pulse width = 12.6 ps , frep = 33.36 MHz )
current effective cavity gain > 300

Oscilloscope :

error signal, not shown as it was too noisy to have in the image
blue : reflection (low bypass filter ), yellow : transmission (resistance of 100 k ohm added), green : piezo signal
1st image : showing lock and scan regions.
2nd image: time zoom on the locked signal

oscillators controller / smartAct:

Frequency and CEP control , the parameters in the photo attached are the best for the moment to see the smooth change of the resonance peaks when operating the motors, and we can stay FSR range and compensate the variation easily.
even though we stayed at closed loop (for easier adjustment), we still managed to lock , will try to switch off later to see if reduces a lot of noise.

Manar Amer wrote:

Today, I installed a power meter at the transmission point of the 1st spherical mirror , transmission 3 ppm (direct from cavity window beam profiler, no filter)

We locked the cavity at 2 different resonances of the fundamental mode, the lock in both cases was stable for a round 1 minute.

at different transmitted power of 33.85 uW ( 11 W average inside cavity) and then locked again at 82.65 uW (27.5 W average inside cavity) transmitted power

Note : the coupling is almost zero for both of the resonances locked !!!!

Oscillator : 33.33 MHz ( 33.356 MHz , frequency read on LAL software)

power injected into amplifier (after injecting into fiber and an EOM) : 3.886 mW (on LAL software)

Amplifier power : 0% (injected power into cavity ~ 300 mW)

Both images of oscilloscope have same voltage scales, only difference timescale and the color code is :

yellow : transmission

blue : reflection

green : piezo voltage

red : error signal

Manar Amer wrote:

Yesterday, with Ronic we locked ThomX cavity on the second resonance

Laser : 33.36 MHz , Amplifier : 0 % (worked with no errors all day)

adding image for the lock on the second resonance (locked), 00 Mode image, fit, Beam measurements

and image of the first resonance signal (not locked)

Info : when locking on the secondary resonance, we aligned better and adjusted on the oscillator CEP and increased the transmission signal

Controllers connected to computer

through Ethernet :

Cavity Mirror motors
Lase lock
oscillator CEP and Frequency motors (easier to follow the drift with this controller, and we can see it moving)

by USB :

Amplifier controller

Manar Amer wrote:

This morning, while trying Guillaume solution of disconnecting the 24 V necessary to the second and third stage and raise the threshold of Temp preamp 1 (to only operate the ampli with first stage only)

Ronic disconnected the 24 volt connection, turned on amplifier LAL software but no MMD3 error or a big temp on Temp preamp 1 , software worked fine with no issue.

we connected the 24 V again and the software worked with no issues.

Still not sure what happened for it to work correctly !!!!!!!!!!

We used the amplifier at 0% all day with no errors (to test , I turned it for 10 minutes @ 10% with no error too)
We changed the lase lock box with ThomX one (having Ethernet connection), it was connected to computer and works ok
Ronic installed a signal amplifier for the PDH error signal. (yet to be fully optimized)
we see a better coupling than before in the cavity.
The dominant mode is 00 mode, but we see many higher order modes, need to alight better.

Manar Amer wrote:

Today with Ronic and Daniele we attempted to lock the cavity, but the alphanov amplifier did not turn on because of an error in MMD3 (related to the third stage)

the new error is having the MMD3 error show on the alarm window of the LAL software, and having the Alarms on the line 3 of the alphanov software red for both EXT/CPU and Laser T Max (never been red before)

this is after a 2-week work stop, but the last time when Daniele changed the fiber connector it worked for 3 hours with no errors.

Ronic, is in contact with Guillaume from Alphanov to fix the issue !!!

Work scheduled all Wednesday, in hopes the issue is fixed by then.

Manar Amer wrote:

Added Note: the coupling we get is at low power, only preamplifier is on (~ 300 mW)

was done at the end due to excitation of higher order modes.

Wanted to improve the fundamental first, then increase the power.

Manar Amer wrote:

On Monday with Daniele,
- we did full characterization of amplifier beam @ 10% amplification, adjusted the telescope accordingly and injected into the cavity aligned and improved on the fundamental mode.
On Tuesday with Daniele and Kevin
- I added a low pass filter between 1 - 1.9 MHz on the reflected signal, to reject the oscillator signal (33.33 MHz)
- removed the external resistors on the signal, only the internal resistance of the oscilloscope used ( transmission : 1 M ohm , Reflection : 50 ohm )
- We connected the motors to control the CEP and adjusted on them until we reached ~ 5 -10% coupling
Images:
- 1st : showing the size of the beam just before injecting into the cavity @ 10%
- 2nd: signal with only improved alignment (not CEP adjustment yet), no low pass filter added yet
- 3rd : zoom on the signals (reflection and error) while adjusting on the CEP
- 4th :attempting to lock the cavity , after getting the max coupling using the CEP motors

Note : the voltage ranges are not the same between the images

Manar Amer wrote:

Yesterday,

we installed the second high power reflecting mirrors at the output of the amplifier.
We aligned and installed a telescope that has adjustable distance between the 2 lenses of -100 mm, and + 200 mm, with approximate diameter at the injection window of ~ 4.5 mm.
Amplifier was turned on only at the first stage only (output power ~ 300 mW) aligned and injected into the cavity.
Measured the repetition frequency of the One Five oscillators, Frep = 33.326239 MHz
Changed the FSR of the cavity to match it.
Using the Piezo scan on the oscillator, we observed 00 Mode, Fundamental. the shape is the same
We see transmission on the diode, but there was zero coupling observed (yet to be investigated experimentally )
- a reason could be the CEP of the oscillator ,
- bad matching of the beam waist position,
- noise from the amplifier (as we were operating it at very low power)
- additional alignment needed,

220

Fri Jun 9 19:51:43 2023

lasers and optics | detectors and electronics | cabling | software

In the morning, we locked on the first resonance. With an increase on the amplifier power @ 20-25% and 30%, which reduced the noise

we manage to get a coupling when improving the CEP up to 55 - 60 % coupling : put there is still a drift on the CEP

The controller for the oscillator frep and CEP produces a lot of noise, even if it is disconnected. we need to switch it off to remove its effect (Kevin will order a new one)

The image attached is of the oscilloscope lock on the first resonance @30% amplifier power ~ 10 W injected into cavity,

transmitted power ~ 36 mW (cavity average power 12 kW)

cavity effective gain > 1200

in the afternoon, we installed and aligned a gentec power meter we can monitor from the computer. (will need to buy a permeant one for ThomX)

there was an issue with the laselock USB connection, yet to be solved.

and the control of the computer.

Manar Amer wrote:

Today with Ronic,

starting with major events that happened (Water circulation + ThomX valves )

Early in the morning a company worked on the water network, it seemed it was not restarted properly so there was no water circulation in the main ThomX pipes.
- There was an error on the ThomX amplifier chiller , which was noticed at the end of the morning work , where we couldn't find the cavity resonance , could be due to the temperature increase of the amplifer.
- Solved : the issue was solved by restarting the water network and the amplifier chiller was restarted an no error found and temp. Stabilized around 25°
Around 12h15 ThomX there was a power cut off for less than a second (micro cutt), which cased all the valves to close, the valve air compressor did not restart after the power cut off, we restarted it with Daniele in the evening with the help of Marie and the valves open around 5-6 bar , you will see then all the controllers green and the valves will open.

Results of the day :

All the power supplies and function generators are under the table, nothing on the table (reduced noise on the signal)
EOM of Oscillator Off (for now, might turn on if needed)
Amplifier on 0% , output ~ 300 mW
Locked on the first resonance of the cavity, lase lock parameters to be optimized better
Transmitted power increased to ~ 267.2 uW
Average power inside cavity = 89. 06 W , peak power = 0.2 kW (pulse width = 12.6 ps , frep = 33.36 MHz )
current effective cavity gain > 300

Oscilloscope :

error signal, not shown as it was too noisy to have in the image
blue : reflection (low bypass filter ), yellow : transmission (resistance of 100 k ohm added), green : piezo signal
1st image : showing lock and scan regions.
2nd image: time zoom on the locked signal

oscillators controller / smartAct:

Frequency and CEP control , the parameters in the photo attached are the best for the moment to see the smooth change of the resonance peaks when operating the motors, and we can stay FSR range and compensate the variation easily.
even though we stayed at closed loop (for easier adjustment), we still managed to lock , will try to switch off later to see if reduces a lot of noise.

Manar Amer wrote:

Today, I installed a power meter at the transmission point of the 1st spherical mirror , transmission 3 ppm (direct from cavity window beam profiler, no filter)

We locked the cavity at 2 different resonances of the fundamental mode, the lock in both cases was stable for a round 1 minute.

at different transmitted power of 33.85 uW ( 11 W average inside cavity) and then locked again at 82.65 uW (27.5 W average inside cavity) transmitted power

Note : the coupling is almost zero for both of the resonances locked !!!!

Oscillator : 33.33 MHz ( 33.356 MHz , frequency read on LAL software)

power injected into amplifier (after injecting into fiber and an EOM) : 3.886 mW (on LAL software)

Amplifier power : 0% (injected power into cavity ~ 300 mW)

Both images of oscilloscope have same voltage scales, only difference timescale and the color code is :

yellow : transmission

blue : reflection

green : piezo voltage

red : error signal

Manar Amer wrote:

Yesterday, with Ronic we locked ThomX cavity on the second resonance

Laser : 33.36 MHz , Amplifier : 0 % (worked with no errors all day)

adding image for the lock on the second resonance (locked), 00 Mode image, fit, Beam measurements

and image of the first resonance signal (not locked)

Info : when locking on the secondary resonance, we aligned better and adjusted on the oscillator CEP and increased the transmission signal

Controllers connected to computer

through Ethernet :

Cavity Mirror motors
Lase lock
oscillator CEP and Frequency motors (easier to follow the drift with this controller, and we can see it moving)

by USB :

Amplifier controller

Manar Amer wrote:

Ronic disconnected the 24 volt connection, turned on amplifier LAL software but no MMD3 error or a big temp on Temp preamp 1 , software worked fine with no issue.

we connected the 24 V again and the software worked with no issues.

Still not sure what happened for it to work correctly !!!!!!!!!!

We used the amplifier at 0% all day with no errors (to test , I turned it for 10 minutes @ 10% with no error too)
We changed the lase lock box with ThomX one (having Ethernet connection), it was connected to computer and works ok
Ronic installed a signal amplifier for the PDH error signal. (yet to be fully optimized)
we see a better coupling than before in the cavity.
The dominant mode is 00 mode, but we see many higher order modes, need to alight better.

Manar Amer wrote:

Today with Ronic and Daniele we attempted to lock the cavity, but the alphanov amplifier did not turn on because of an error in MMD3 (related to the third stage)

this is after a 2-week work stop, but the last time when Daniele changed the fiber connector it worked for 3 hours with no errors.

Ronic, is in contact with Guillaume from Alphanov to fix the issue !!!

Work scheduled all Wednesday, in hopes the issue is fixed by then.

Manar Amer wrote:

Added Note: the coupling we get is at low power, only preamplifier is on (~ 300 mW)

was done at the end due to excitation of higher order modes.

Wanted to improve the fundamental first, then increase the power.

Manar Amer wrote:

On Monday with Daniele,
- we did full characterization of amplifier beam @ 10% amplification, adjusted the telescope accordingly and injected into the cavity aligned and improved on the fundamental mode.
On Tuesday with Daniele and Kevin
- I added a low pass filter between 1 - 1.9 MHz on the reflected signal, to reject the oscillator signal (33.33 MHz)
- removed the external resistors on the signal, only the internal resistance of the oscilloscope used ( transmission : 1 M ohm , Reflection : 50 ohm )
- We connected the motors to control the CEP and adjusted on them until we reached ~ 5 -10% coupling
Images:
- 1st : showing the size of the beam just before injecting into the cavity @ 10%
- 2nd: signal with only improved alignment (not CEP adjustment yet), no low pass filter added yet
- 3rd : zoom on the signals (reflection and error) while adjusting on the CEP
- 4th :attempting to lock the cavity , after getting the max coupling using the CEP motors

Note : the voltage ranges are not the same between the images

Manar Amer wrote:

Yesterday,

we installed the second high power reflecting mirrors at the output of the amplifier.
We aligned and installed a telescope that has adjustable distance between the 2 lenses of -100 mm, and + 200 mm, with approximate diameter at the injection window of ~ 4.5 mm.
Amplifier was turned on only at the first stage only (output power ~ 300 mW) aligned and injected into the cavity.
Measured the repetition frequency of the One Five oscillators, Frep = 33.326239 MHz
Changed the FSR of the cavity to match it.
Using the Piezo scan on the oscillator, we observed 00 Mode, Fundamental. the shape is the same
We see transmission on the diode, but there was zero coupling observed (yet to be investigated experimentally )
- a reason could be the CEP of the oscillator ,
- bad matching of the beam waist position,
- noise from the amplifier (as we were operating it at very low power)
- additional alignment needed,

Attachment 1: tek00001_noise_reduced_first_resonance.png

Attachment 2: tek00000_cavity_lock_with_noise_from_odcillator_controller.png

219

Thu Jun 8 11:12:20 2023

the fast lock loop on the EOM has been disabled for the moment.
it has to be installed back to improve the stability at a better CEP.

at present, the FP-cavity power is estimated at ~ 90W (~270µW in transmission of ~3ppm mirrors) for ~300mW of total power coming from the laser amp.

Ronic Chiche wrote:

lastely, we can also make an optical phase noise measurement to check if the Alphanov amplifier does not add some noise.

Ronic Chiche wrote:

then, we locked pretty easily on this first secondary resonance, with a coupling around some % when we adjust the CEP motor.

we tried to lock on the main resonance but it is too noisy and unstable.
it seems we really need high BW feedback.

A loop with an AOM could be easier to install and manage... but at the price of a loss of power before the laser amplifier...

Ronic Chiche wrote:

the last tries to lock the 33MHz + amplifier to the 30k Finesse FP-cavity were unsuccessful.

some informations:

- by comparison, the PZT sensitivity for the 133MHz laser is given to 3.9Hz/V for Frep <=> 8.5MHz/V for optical frequency.

- by comparison, the PZT sensitivity for the NKT CW laser is given 10pm/100V for Wavelength <=> 30MHz/V for optical frequency

218

Wed Jun 7 21:46:50 2023

lasers and optics | detectors and electronics | cabling | software

Today with Ronic,

starting with major events that happened (Water circulation + ThomX valves )

Early in the morning a company worked on the water network, it seemed it was not restarted properly so there was no water circulation in the main ThomX pipes.
- There was an error on the ThomX amplifier chiller , which was noticed at the end of the morning work , where we couldn't find the cavity resonance , could be due to the temperature increase of the amplifer.
- Solved : the issue was solved by restarting the water network and the amplifier chiller was restarted an no error found and temp. Stabilized around 25°
Around 12h15 ThomX there was a power cut off for less than a second (micro cutt), which cased all the valves to close, the valve air compressor did not restart after the power cut off, we restarted it with Daniele in the evening with the help of Marie and the valves open around 5-6 bar , you will see then all the controllers green and the valves will open.

Results of the day :

All the power supplies and function generators are under the table, nothing on the table (reduced noise on the signal)
EOM of Oscillator Off (for now, might turn on if needed)
Amplifier on 0% , output ~ 300 mW
Locked on the first resonance of the cavity, lase lock parameters to be optimized better
Transmitted power increased to ~ 267.2 uW
Average power inside cavity = 89. 06 W , peak power = 0.2 kW (pulse width = 12.6 ps , frep = 33.36 MHz )
current effective cavity gain > 300

Oscilloscope :

error signal, not shown as it was too noisy to have in the image
blue : reflection (low bypass filter ), yellow : transmission (resistance of 100 k ohm added), green : piezo signal
1st image : showing lock and scan regions.
2nd image: time zoom on the locked signal

oscillators controller / smartAct:

Frequency and CEP control , the parameters in the photo attached are the best for the moment to see the smooth change of the resonance peaks when operating the motors, and we can stay FSR range and compensate the variation easily.
even though we stayed at closed loop (for easier adjustment), we still managed to lock , will try to switch off later to see if reduces a lot of noise.

Manar Amer wrote:

Today, I installed a power meter at the transmission point of the 1st spherical mirror , transmission 3 ppm (direct from cavity window beam profiler, no filter)

We locked the cavity at 2 different resonances of the fundamental mode, the lock in both cases was stable for a round 1 minute.

at different transmitted power of 33.85 uW ( 11 W average inside cavity) and then locked again at 82.65 uW (27.5 W average inside cavity) transmitted power

Note : the coupling is almost zero for both of the resonances locked !!!!

Oscillator : 33.33 MHz ( 33.356 MHz , frequency read on LAL software)

power injected into amplifier (after injecting into fiber and an EOM) : 3.886 mW (on LAL software)

Amplifier power : 0% (injected power into cavity ~ 300 mW)

Both images of oscilloscope have same voltage scales, only difference timescale and the color code is :

yellow : transmission

blue : reflection

green : piezo voltage

red : error signal

Manar Amer wrote:

Yesterday, with Ronic we locked ThomX cavity on the second resonance

Laser : 33.36 MHz , Amplifier : 0 % (worked with no errors all day)

adding image for the lock on the second resonance (locked), 00 Mode image, fit, Beam measurements

and image of the first resonance signal (not locked)

Info : when locking on the secondary resonance, we aligned better and adjusted on the oscillator CEP and increased the transmission signal

Controllers connected to computer

through Ethernet :

Cavity Mirror motors
Lase lock
oscillator CEP and Frequency motors (easier to follow the drift with this controller, and we can see it moving)

by USB :

Amplifier controller

Manar Amer wrote:

Ronic disconnected the 24 volt connection, turned on amplifier LAL software but no MMD3 error or a big temp on Temp preamp 1 , software worked fine with no issue.

we connected the 24 V again and the software worked with no issues.

Still not sure what happened for it to work correctly !!!!!!!!!!

We used the amplifier at 0% all day with no errors (to test , I turned it for 10 minutes @ 10% with no error too)
We changed the lase lock box with ThomX one (having Ethernet connection), it was connected to computer and works ok
Ronic installed a signal amplifier for the PDH error signal. (yet to be fully optimized)
we see a better coupling than before in the cavity.
The dominant mode is 00 mode, but we see many higher order modes, need to alight better.

Manar Amer wrote:

Today with Ronic and Daniele we attempted to lock the cavity, but the alphanov amplifier did not turn on because of an error in MMD3 (related to the third stage)

this is after a 2-week work stop, but the last time when Daniele changed the fiber connector it worked for 3 hours with no errors.

Ronic, is in contact with Guillaume from Alphanov to fix the issue !!!

Work scheduled all Wednesday, in hopes the issue is fixed by then.

Manar Amer wrote:

Added Note: the coupling we get is at low power, only preamplifier is on (~ 300 mW)

was done at the end due to excitation of higher order modes.

Wanted to improve the fundamental first, then increase the power.

Manar Amer wrote:

On Monday with Daniele,
- we did full characterization of amplifier beam @ 10% amplification, adjusted the telescope accordingly and injected into the cavity aligned and improved on the fundamental mode.
On Tuesday with Daniele and Kevin
- I added a low pass filter between 1 - 1.9 MHz on the reflected signal, to reject the oscillator signal (33.33 MHz)
- removed the external resistors on the signal, only the internal resistance of the oscilloscope used ( transmission : 1 M ohm , Reflection : 50 ohm )
- We connected the motors to control the CEP and adjusted on them until we reached ~ 5 -10% coupling
Images:
- 1st : showing the size of the beam just before injecting into the cavity @ 10%
- 2nd: signal with only improved alignment (not CEP adjustment yet), no low pass filter added yet
- 3rd : zoom on the signals (reflection and error) while adjusting on the CEP
- 4th :attempting to lock the cavity , after getting the max coupling using the CEP motors

Note : the voltage ranges are not the same between the images

Manar Amer wrote:

Yesterday,

we installed the second high power reflecting mirrors at the output of the amplifier.
We aligned and installed a telescope that has adjustable distance between the 2 lenses of -100 mm, and + 200 mm, with approximate diameter at the injection window of ~ 4.5 mm.
Amplifier was turned on only at the first stage only (output power ~ 300 mW) aligned and injected into the cavity.
Measured the repetition frequency of the One Five oscillators, Frep = 33.326239 MHz
Changed the FSR of the cavity to match it.
Using the Piezo scan on the oscillator, we observed 00 Mode, Fundamental. the shape is the same
We see transmission on the diode, but there was zero coupling observed (yet to be investigated experimentally )
- a reason could be the CEP of the oscillator ,
- bad matching of the beam waist position,
- noise from the amplifier (as we were operating it at very low power)
- additional alignment needed,

Attachment 1: tek00001.png

Attachment 2: 20230607_183626_Frep_CEP_motors_smartAct.jpg

Attachment 3: 20230607_183641_transmitted_power.jpg

Attachment 4: tek00002.png

217

Tue Jun 6 15:52:59 2023

lastely, we can also make an optical phase noise measurement to check if the Alphanov amplifier does not add some noise.

Ronic Chiche wrote:

then, we locked pretty easily on this first secondary resonance, with a coupling around some % when we adjust the CEP motor.

we tried to lock on the main resonance but it is too noisy and unstable.
it seems we really need high BW feedback.

A loop with an AOM could be easier to install and manage... but at the price of a loss of power before the laser amplifier...

Ronic Chiche wrote:

the last tries to lock the 33MHz + amplifier to the 30k Finesse FP-cavity were unsuccessful.

some informations:

- by comparison, the PZT sensitivity for the 133MHz laser is given to 3.9Hz/V for Frep <=> 8.5MHz/V for optical frequency.

- by comparison, the PZT sensitivity for the NKT CW laser is given 10pm/100V for Wavelength <=> 30MHz/V for optical frequency

Attachment 1: M250_Video_Amplifier.pdf

Attachment 2: M250_manual.pdf

216

Tue Jun 6 01:12:11 2023

lasers and optics | detectors and electronics | cabling | software

Today, I installed a power meter at the transmission point of the 1st spherical mirror , transmission 3 ppm (direct from cavity window beam profiler, no filter)

We locked the cavity at 2 different resonances of the fundamental mode, the lock in both cases was stable for a round 1 minute.

at different transmitted power of 33.85 uW ( 11 W average inside cavity) and then locked again at 82.65 uW (27.5 W average inside cavity) transmitted power

Note : the coupling is almost zero for both of the resonances locked !!!!

Oscillator : 33.33 MHz ( 33.356 MHz , frequency read on LAL software)

power injected into amplifier (after injecting into fiber and an EOM) : 3.886 mW (on LAL software)

Amplifier power : 0% (injected power into cavity ~ 300 mW)

Both images of oscilloscope have same voltage scales, only difference timescale and the color code is :

yellow : transmission

blue : reflection

green : piezo voltage

red : error signal

Manar Amer wrote:

Yesterday, with Ronic we locked ThomX cavity on the second resonance

Laser : 33.36 MHz , Amplifier : 0 % (worked with no errors all day)

adding image for the lock on the second resonance (locked), 00 Mode image, fit, Beam measurements

and image of the first resonance signal (not locked)

Info : when locking on the secondary resonance, we aligned better and adjusted on the oscillator CEP and increased the transmission signal

Controllers connected to computer

through Ethernet :

Cavity Mirror motors
Lase lock
oscillator CEP and Frequency motors (easier to follow the drift with this controller, and we can see it moving)

by USB :

Amplifier controller

Manar Amer wrote:

Ronic disconnected the 24 volt connection, turned on amplifier LAL software but no MMD3 error or a big temp on Temp preamp 1 , software worked fine with no issue.

we connected the 24 V again and the software worked with no issues.

Still not sure what happened for it to work correctly !!!!!!!!!!

We used the amplifier at 0% all day with no errors (to test , I turned it for 10 minutes @ 10% with no error too)
We changed the lase lock box with ThomX one (having Ethernet connection), it was connected to computer and works ok
Ronic installed a signal amplifier for the PDH error signal. (yet to be fully optimized)
we see a better coupling than before in the cavity.
The dominant mode is 00 mode, but we see many higher order modes, need to alight better.

Manar Amer wrote:

Today with Ronic and Daniele we attempted to lock the cavity, but the alphanov amplifier did not turn on because of an error in MMD3 (related to the third stage)

this is after a 2-week work stop, but the last time when Daniele changed the fiber connector it worked for 3 hours with no errors.

Ronic, is in contact with Guillaume from Alphanov to fix the issue !!!

Work scheduled all Wednesday, in hopes the issue is fixed by then.

Manar Amer wrote:

Added Note: the coupling we get is at low power, only preamplifier is on (~ 300 mW)

was done at the end due to excitation of higher order modes.

Wanted to improve the fundamental first, then increase the power.

Manar Amer wrote:

On Monday with Daniele,
- we did full characterization of amplifier beam @ 10% amplification, adjusted the telescope accordingly and injected into the cavity aligned and improved on the fundamental mode.
On Tuesday with Daniele and Kevin
- I added a low pass filter between 1 - 1.9 MHz on the reflected signal, to reject the oscillator signal (33.33 MHz)
- removed the external resistors on the signal, only the internal resistance of the oscilloscope used ( transmission : 1 M ohm , Reflection : 50 ohm )
- We connected the motors to control the CEP and adjusted on them until we reached ~ 5 -10% coupling
Images:
- 1st : showing the size of the beam just before injecting into the cavity @ 10%
- 2nd: signal with only improved alignment (not CEP adjustment yet), no low pass filter added yet
- 3rd : zoom on the signals (reflection and error) while adjusting on the CEP
- 4th :attempting to lock the cavity , after getting the max coupling using the CEP motors

Note : the voltage ranges are not the same between the images

Manar Amer wrote:

Yesterday,

we installed the second high power reflecting mirrors at the output of the amplifier.
We aligned and installed a telescope that has adjustable distance between the 2 lenses of -100 mm, and + 200 mm, with approximate diameter at the injection window of ~ 4.5 mm.
Amplifier was turned on only at the first stage only (output power ~ 300 mW) aligned and injected into the cavity.
Measured the repetition frequency of the One Five oscillators, Frep = 33.326239 MHz
Changed the FSR of the cavity to match it.
Using the Piezo scan on the oscillator, we observed 00 Mode, Fundamental. the shape is the same
We see transmission on the diode, but there was zero coupling observed (yet to be investigated experimentally )
- a reason could be the CEP of the oscillator ,
- bad matching of the beam waist position,
- noise from the amplifier (as we were operating it at very low power)
- additional alignment needed,

Attachment 1: 20230605_tek00001_33uW.png

Attachment 2: 20230605_tek00002_82uW.png

215

Fri Jun 2 10:54:25 2023

lasers and optics | detectors and electronics | cabling | software

Yesterday, with Ronic we locked ThomX cavity on the second resonance

Laser : 33.36 MHz , Amplifier : 0 % (worked with no errors all day)

adding image for the lock on the second resonance (locked), 00 Mode image, fit, Beam measurements

and image of the first resonance signal (not locked)

Info : when locking on the secondary resonance, we aligned better and adjusted on the oscillator CEP and increased the transmission signal

Controllers connected to computer

through Ethernet :

Cavity Mirror motors
Lase lock
oscillator CEP and Frequency motors (easier to follow the drift with this controller, and we can see it moving)

by USB :

Amplifier controller

Manar Amer wrote:

Ronic disconnected the 24 volt connection, turned on amplifier LAL software but no MMD3 error or a big temp on Temp preamp 1 , software worked fine with no issue.

we connected the 24 V again and the software worked with no issues.

Still not sure what happened for it to work correctly !!!!!!!!!!

We used the amplifier at 0% all day with no errors (to test , I turned it for 10 minutes @ 10% with no error too)
We changed the lase lock box with ThomX one (having Ethernet connection), it was connected to computer and works ok
Ronic installed a signal amplifier for the PDH error signal. (yet to be fully optimized)
we see a better coupling than before in the cavity.
The dominant mode is 00 mode, but we see many higher order modes, need to alight better.

Manar Amer wrote:

Today with Ronic and Daniele we attempted to lock the cavity, but the alphanov amplifier did not turn on because of an error in MMD3 (related to the third stage)

this is after a 2-week work stop, but the last time when Daniele changed the fiber connector it worked for 3 hours with no errors.

Ronic, is in contact with Guillaume from Alphanov to fix the issue !!!

Work scheduled all Wednesday, in hopes the issue is fixed by then.

Manar Amer wrote:

Added Note: the coupling we get is at low power, only preamplifier is on (~ 300 mW)

was done at the end due to excitation of higher order modes.

Wanted to improve the fundamental first, then increase the power.

Manar Amer wrote:

On Monday with Daniele,
- we did full characterization of amplifier beam @ 10% amplification, adjusted the telescope accordingly and injected into the cavity aligned and improved on the fundamental mode.
On Tuesday with Daniele and Kevin
- I added a low pass filter between 1 - 1.9 MHz on the reflected signal, to reject the oscillator signal (33.33 MHz)
- removed the external resistors on the signal, only the internal resistance of the oscilloscope used ( transmission : 1 M ohm , Reflection : 50 ohm )
- We connected the motors to control the CEP and adjusted on them until we reached ~ 5 -10% coupling
Images:
- 1st : showing the size of the beam just before injecting into the cavity @ 10%
- 2nd: signal with only improved alignment (not CEP adjustment yet), no low pass filter added yet
- 3rd : zoom on the signals (reflection and error) while adjusting on the CEP
- 4th :attempting to lock the cavity , after getting the max coupling using the CEP motors

Note : the voltage ranges are not the same between the images

Manar Amer wrote:

Yesterday,

we installed the second high power reflecting mirrors at the output of the amplifier.
We aligned and installed a telescope that has adjustable distance between the 2 lenses of -100 mm, and + 200 mm, with approximate diameter at the injection window of ~ 4.5 mm.
Amplifier was turned on only at the first stage only (output power ~ 300 mW) aligned and injected into the cavity.
Measured the repetition frequency of the One Five oscillators, Frep = 33.326239 MHz
Changed the FSR of the cavity to match it.
Using the Piezo scan on the oscillator, we observed 00 Mode, Fundamental. the shape is the same
We see transmission on the diode, but there was zero coupling observed (yet to be investigated experimentally )
- a reason could be the CEP of the oscillator ,
- bad matching of the beam waist position,
- noise from the amplifier (as we were operating it at very low power)
- additional alignment needed,

Attachment 1: tek00003_secondary_resonance_fundamental_mode_lock.png

Attachment 2: tek0002CH1.isf

Attachment 3: tek0002CH2.isf

Attachment 4: tek0002CH3.isf

Attachment 5: tek0002CH4.isf

Attachment 6: 20230602_00mode_second_resonance.jpg

Attachment 7: 20230602_00mode_second_resonance_fit.jpg

Attachment 8: 20230602_00mode_second_resonance_measurements.jpg

Attachment 9: tek00002_first_resonance_fundamental_mode_signal.png

Attachment 10: tek0001CH1.isf

Attachment 11: tek0001CH2.isf

Attachment 12: tek0001CH3.isf

Attachment 13: tek0001CH4.isf

214

Thu Jun 1 18:15:04 2023

then, we locked pretty easily on this first secondary resonance, with a coupling around some % when we adjust the CEP motor.

we tried to lock on the main resonance but it is too noisy and unstable.
it seems we really need high BW feedback.

A loop with an AOM could be easier to install and manage... but at the price of a loss of power before the laser amplifier...

Ronic Chiche wrote:

the last tries to lock the 33MHz + amplifier to the 30k Finesse FP-cavity were unsuccessful.

some informations:

- by comparison, the PZT sensitivity for the 133MHz laser is given to 3.9Hz/V for Frep <=> 8.5MHz/V for optical frequency.

- by comparison, the PZT sensitivity for the NKT CW laser is given 10pm/100V for Wavelength <=> 30MHz/V for optical frequency

213

Thu Jun 1 10:31:45 2023

the last tries to lock the 33MHz + amplifier to the 30k Finesse FP-cavity were unsuccessful.

some informations:

- by comparison, the PZT sensitivity for the 133MHz laser is given to 3.9Hz/V for Frep <=> 8.5MHz/V for optical frequency.

- by comparison, the PZT sensitivity for the NKT CW laser is given 10pm/100V for Wavelength <=> 30MHz/V for optical frequency

Attachment 1: 120705_Displacement_of_cylindrical_piezo_ceramics.xls

212

Tue May 30 18:32:37 2023

lasers and optics | detectors and electronics | cabling | software

Ronic disconnected the 24 volt connection, turned on amplifier LAL software but no MMD3 error or a big temp on Temp preamp 1 , software worked fine with no issue.

we connected the 24 V again and the software worked with no issues.

Still not sure what happened for it to work correctly !!!!!!!!!!

We used the amplifier at 0% all day with no errors (to test , I turned it for 10 minutes @ 10% with no error too)
We changed the lase lock box with ThomX one (having Ethernet connection), it was connected to computer and works ok
Ronic installed a signal amplifier for the PDH error signal. (yet to be fully optimized)
we see a better coupling than before in the cavity.
The dominant mode is 00 mode, but we see many higher order modes, need to alight better.

Manar Amer wrote:

Today with Ronic and Daniele we attempted to lock the cavity, but the alphanov amplifier did not turn on because of an error in MMD3 (related to the third stage)

this is after a 2-week work stop, but the last time when Daniele changed the fiber connector it worked for 3 hours with no errors.

Ronic, is in contact with Guillaume from Alphanov to fix the issue !!!

Work scheduled all Wednesday, in hopes the issue is fixed by then.

Manar Amer wrote:

Added Note: the coupling we get is at low power, only preamplifier is on (~ 300 mW)

was done at the end due to excitation of higher order modes.

Wanted to improve the fundamental first, then increase the power.

Manar Amer wrote:

On Monday with Daniele,
- we did full characterization of amplifier beam @ 10% amplification, adjusted the telescope accordingly and injected into the cavity aligned and improved on the fundamental mode.
On Tuesday with Daniele and Kevin
- I added a low pass filter between 1 - 1.9 MHz on the reflected signal, to reject the oscillator signal (33.33 MHz)
- removed the external resistors on the signal, only the internal resistance of the oscilloscope used ( transmission : 1 M ohm , Reflection : 50 ohm )
- We connected the motors to control the CEP and adjusted on them until we reached ~ 5 -10% coupling
Images:
- 1st : showing the size of the beam just before injecting into the cavity @ 10%
- 2nd: signal with only improved alignment (not CEP adjustment yet), no low pass filter added yet
- 3rd : zoom on the signals (reflection and error) while adjusting on the CEP
- 4th :attempting to lock the cavity , after getting the max coupling using the CEP motors

Note : the voltage ranges are not the same between the images

Manar Amer wrote:

Yesterday,

we installed the second high power reflecting mirrors at the output of the amplifier.
We aligned and installed a telescope that has adjustable distance between the 2 lenses of -100 mm, and + 200 mm, with approximate diameter at the injection window of ~ 4.5 mm.
Amplifier was turned on only at the first stage only (output power ~ 300 mW) aligned and injected into the cavity.
Measured the repetition frequency of the One Five oscillators, Frep = 33.326239 MHz
Changed the FSR of the cavity to match it.
Using the Piezo scan on the oscillator, we observed 00 Mode, Fundamental. the shape is the same
We see transmission on the diode, but there was zero coupling observed (yet to be investigated experimentally )
- a reason could be the CEP of the oscillator ,
- bad matching of the beam waist position,
- noise from the amplifier (as we were operating it at very low power)
- additional alignment needed,

Attachment 1: tek00000.png

211

Mon May 22 16:07:12 2023

Today with Ronic and Daniele we attempted to lock the cavity, but the alphanov amplifier did not turn on because of an error in MMD3 (related to the third stage)

this is after a 2-week work stop, but the last time when Daniele changed the fiber connector it worked for 3 hours with no errors.

Ronic, is in contact with Guillaume from Alphanov to fix the issue !!!

Work scheduled all Wednesday, in hopes the issue is fixed by then.

Manar Amer wrote:

Added Note: the coupling we get is at low power, only preamplifier is on (~ 300 mW)

was done at the end due to excitation of higher order modes.

Wanted to improve the fundamental first, then increase the power.

Manar Amer wrote:

On Monday with Daniele,
- we did full characterization of amplifier beam @ 10% amplification, adjusted the telescope accordingly and injected into the cavity aligned and improved on the fundamental mode.
On Tuesday with Daniele and Kevin
- I added a low pass filter between 1 - 1.9 MHz on the reflected signal, to reject the oscillator signal (33.33 MHz)
- removed the external resistors on the signal, only the internal resistance of the oscilloscope used ( transmission : 1 M ohm , Reflection : 50 ohm )
- We connected the motors to control the CEP and adjusted on them until we reached ~ 5 -10% coupling
Images:
- 1st : showing the size of the beam just before injecting into the cavity @ 10%
- 2nd: signal with only improved alignment (not CEP adjustment yet), no low pass filter added yet
- 3rd : zoom on the signals (reflection and error) while adjusting on the CEP
- 4th :attempting to lock the cavity , after getting the max coupling using the CEP motors

Note : the voltage ranges are not the same between the images

Manar Amer wrote:

Yesterday,

we installed the second high power reflecting mirrors at the output of the amplifier.
We aligned and installed a telescope that has adjustable distance between the 2 lenses of -100 mm, and + 200 mm, with approximate diameter at the injection window of ~ 4.5 mm.
Amplifier was turned on only at the first stage only (output power ~ 300 mW) aligned and injected into the cavity.
Measured the repetition frequency of the One Five oscillators, Frep = 33.326239 MHz
Changed the FSR of the cavity to match it.
Using the Piezo scan on the oscillator, we observed 00 Mode, Fundamental. the shape is the same
We see transmission on the diode, but there was zero coupling observed (yet to be investigated experimentally )
- a reason could be the CEP of the oscillator ,
- bad matching of the beam waist position,
- noise from the amplifier (as we were operating it at very low power)
- additional alignment needed,

Attachment 1: 2023-05-22_MMD3_error_on_alarm_window.jpg

Attachment 2: 2023-05-22_alphanov_software.jpg

210

Wed Apr 19 16:41:46 2023

Added Note: the coupling we get is at low power, only preamplifier is on (~ 300 mW)

was done at the end due to excitation of higher order modes.

Wanted to improve the fundamental first, then increase the power.

Manar Amer wrote:

On Monday with Daniele,
- we did full characterization of amplifier beam @ 10% amplification, adjusted the telescope accordingly and injected into the cavity aligned and improved on the fundamental mode.
On Tuesday with Daniele and Kevin
- I added a low pass filter between 1 - 1.9 MHz on the reflected signal, to reject the oscillator signal (33.33 MHz)
- removed the external resistors on the signal, only the internal resistance of the oscilloscope used ( transmission : 1 M ohm , Reflection : 50 ohm )
- We connected the motors to control the CEP and adjusted on them until we reached ~ 5 -10% coupling
Images:
- 1st : showing the size of the beam just before injecting into the cavity @ 10%
- 2nd: signal with only improved alignment (not CEP adjustment yet), no low pass filter added yet
- 3rd : zoom on the signals (reflection and error) while adjusting on the CEP
- 4th :attempting to lock the cavity , after getting the max coupling using the CEP motors

Note : the voltage ranges are not the same between the images

Manar Amer wrote:

Yesterday,

we installed the second high power reflecting mirrors at the output of the amplifier.
We aligned and installed a telescope that has adjustable distance between the 2 lenses of -100 mm, and + 200 mm, with approximate diameter at the injection window of ~ 4.5 mm.
Amplifier was turned on only at the first stage only (output power ~ 300 mW) aligned and injected into the cavity.
Measured the repetition frequency of the One Five oscillators, Frep = 33.326239 MHz
Changed the FSR of the cavity to match it.
Using the Piezo scan on the oscillator, we observed 00 Mode, Fundamental. the shape is the same
We see transmission on the diode, but there was zero coupling observed (yet to be investigated experimentally )
- a reason could be the CEP of the oscillator ,
- bad matching of the beam waist position,
- noise from the amplifier (as we were operating it at very low power)
- additional alignment needed,

209

Wed Apr 19 16:39:28 2023

On Monday with Daniele,
- we did full characterization of amplifier beam @ 10% amplification, adjusted the telescope accordingly and injected into the cavity aligned and improved on the fundamental mode.
On Tuesday with Daniele and Kevin
- I added a low pass filter between 1 - 1.9 MHz on the reflected signal, to reject the oscillator signal (33.33 MHz)
- removed the external resistors on the signal, only the internal resistance of the oscilloscope used ( transmission : 1 M ohm , Reflection : 50 ohm )
- We connected the motors to control the CEP and adjusted on them until we reached ~ 5 -10% coupling
Images:
- 1st : showing the size of the beam just before injecting into the cavity @ 10%
- 2nd: signal with only improved alignment (not CEP adjustment yet), no low pass filter added yet
- 3rd : zoom on the signals (reflection and error) while adjusting on the CEP
- 4th :attempting to lock the cavity , after getting the max coupling using the CEP motors

Note : the voltage ranges are not the same between the images

Manar Amer wrote:

Yesterday,

we installed the second high power reflecting mirrors at the output of the amplifier.
We aligned and installed a telescope that has adjustable distance between the 2 lenses of -100 mm, and + 200 mm, with approximate diameter at the injection window of ~ 4.5 mm.
Amplifier was turned on only at the first stage only (output power ~ 300 mW) aligned and injected into the cavity.
Measured the repetition frequency of the One Five oscillators, Frep = 33.326239 MHz
Changed the FSR of the cavity to match it.
Using the Piezo scan on the oscillator, we observed 00 Mode, Fundamental. the shape is the same
We see transmission on the diode, but there was zero coupling observed (yet to be investigated experimentally )
- a reason could be the CEP of the oscillator ,
- bad matching of the beam waist position,
- noise from the amplifier (as we were operating it at very low power)
- additional alignment needed,

Attachment 1: 20230418_size_of_beam_before_injection_window_at_10percetage_ampli.jpg

Attachment 2: 20230418_coupling_at_the_start_only_alignment_improved1.jpg

Attachment 3: 20230418_zoom_on_Oscilliscope_signal_fundamental_mode.jpg

Attachment 4: 20230418_coupling_after_improving_it_with_regulator_on_attempting_to_lock.jpg

208

Thu Apr 13 17:48:49 2023

Yesterday,

we installed the second high power reflecting mirrors at the output of the amplifier.
We aligned and installed a telescope that has adjustable distance between the 2 lenses of -100 mm, and + 200 mm, with approximate diameter at the injection window of ~ 4.5 mm.
Amplifier was turned on only at the first stage only (output power ~ 300 mW) aligned and injected into the cavity.
Measured the repetition frequency of the One Five oscillators, Frep = 33.326239 MHz
Changed the FSR of the cavity to match it.
Using the Piezo scan on the oscillator, we observed 00 Mode, Fundamental. the shape is the same
We see transmission on the diode, but there was zero coupling observed (yet to be investigated experimentally )
- a reason could be the CEP of the oscillator ,
- bad matching of the beam waist position,
- noise from the amplifier (as we were operating it at very low power)
- additional alignment needed,

Attachment 1: 20230412_pulsed_cav_mode.bmp

207

Tue Apr 11 16:58:16 2023

FP Finesse measurement using CW

This morning, with Ronic and Daniele, we locked the cavity again (The lock was relatively easy and stable during the reading of the finesse)

We took 2 reading of finesse

1st : @ 33.2808 MHz (what the cavity length was at) : Finesse = 27 024

2nd : @ 33.3382 MHz (adjusted to match the pulsed laser) : Finesse = 30 433

The difference between the 2 is the FSR, during the change we also did some alignment to counter the reduced transmitted power.

We took an image of the beam profile before and after changing FSR and there was ~ 70 um change in the beam position on the Horizontal axis of the beam.

Manar Amer wrote:

This morning with Daniele and Viktor,

- we confirmed the "potato" mode was well centered on the injected beam and was not due to some misalignment of the injected beam compared to the cavity axis.
we look at the reflected beam during a lock. we can see the direct reflected beam superposed with the cavity mode (cf attached image).

- then we assumed the "potato" mode problem could come from the too short distance between spherical mirrors which introduces ellipticity and finally can lead to some instability.
we manage to move further spherical mirrors S2 and S3 by moving them from 1 350 000 to 800 000 steps.
=> we increased the distance by 2x 550 000 steps (with 6µm for 1000 steps) => we increased the distance between spherical mirrors by 6.6 mm
the new mode shrinked a lot and at the end was spherical at 73%.
the mode size is now about 4400 x 6000 µm but with the major and minor axis still at 45° !

Manar Amer wrote:

Yesterday morning we locked the cavity on a strange mode in the cavity (we call it mode, but not sure what it is ??)

we also managed to lock on a higher order mode 02

we get an estimated 30% coupling (expected value), and note that we have not installed a telescope yet.

Manar Amer wrote:

Today, we prepared lenses for a telescope for the CW laser injection into the cavity, yet to be installed

Image of the transmission at P4 attached, an estimation of the beam size of the mode see is ~ 5.5 mm

The vacuum in the 2 optical cavities is decreasing but slowly. today it is 2.6 - 2.4 * 10^-7 mbar

Manar Amer wrote:

Last week, with Ronic and Victor we aligned the cavity using CW laser (Koheras)

we have also installed 4 mirrors in the cavity with the best theoretical qualities (serial number and images included)
- The Plan ULE mirror P4 thickness was not compatible with the piezoelectric mount. We had to install a metal spacer behind the mirror to be able to fix it. the metal spacers in from ThorLabs made from INOX, It is 1 inch diameter (25.4 mm), we drilled a hole in the middle of 15 mm in the Workshop in bat 200. Then cleaned it using an ultrasound bath in pure water, using a small Ultrasound bath machine in Maverics platform Vide and Surfaces next to ThomX eglo.
- This gives some difficulties in imaging the transmission at P4. To help with the imaging, we used the plastic #D printed irises that Yann made long time ago
- we took images of the mode inside the cavity at P4 transmission.

We also observed some oxidization on the metal bars of the controllers, more on the side of S2 and P4. we are yet to test the motion of the motors in the z-axis.
Friday evening we closed the windows using a new copper rings (last one we have, Ronic placed a new order).
The pump was turned on by Bruno and Eric yesterday afternoon. The current vacuum level is 6-7*10^-6 mbar

the pre and the turbo pimps are on so still too noisy to work, we have access all day tomorrow.

Attachment 1: 20230411_first_Finesse_reading.JPG

Attachment 2: 20230411_second_Finesse_reading.JPG

Attachment 3: 20230411_Beam_Profile_position_differance_when_changing_FSR.JPG

206

Fri Apr 7 15:56:40 2023