| ID |
Date |
Author |
Status |
Type |
Category |
Location |
Title |
|
208
|
Tue Apr 2 08:39:17 2024 |
Xinyi Lu | Fixed | info | lasers and optics | Optical room | High power experiments (500kW) | Last week, we achieved a stable intracavity average power of 500kW, limited by amplifier power. The experimental data are shown in Figure 1.
- We measured the transmitted laser with a power meter in the windows behind M2 and M4 respectively, and the results were consistent, so the measurements were credible.
- There is only one transmitted laser spot behind both M2 and M4.
- We measured 10-minute locking data at different powers (Figure 2). 480 kW data was not optimized, and we will add 500 kW locking data later.
- We compared cavity modes at different powers (Figure 3). There are fluctuations because we only saved one data at one power. More data will be collected for averaging later.
- After finishing the high-power experiments, we will measure the finesse and the transmission of the mirrors used. As well as the pulse duration, spectrum, phase noise, and repetition rate of the laser.
| Xinyi Lu wrote: |
|
Today, Ronic, Daniele, Aurélien and I measured the amplifier power and mirror transmission.
| Current (A) |
0 (2rd stage) |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
7.5 |
8 |
| Power (W) |
1 |
1.8 |
11.8 |
23.5 |
35.5 |
47 |
57.5 |
66.9 |
70.7 |
74.9 |
For transmission measurements, we used the same new mirrors as Sbox and ThomX, and installed an iris and a 2-inch mount to block the scattering laser.
The angle of incidence during the measurement was about 0.5°. We changed the angle and the measurements remained the same.
| Mirror Number |
PL-0898 |
PL-10978 |
| Nominal Value |
3 ppm |
115 ppm |
| Measured Value |
1.75 ppm |
113 ppm |
If the mirror being used also has a transmission of 1.75 ppm, the original 270kW is actually 463kW!!! The gain is 6549 and the finesse is 28585 (70% coupling).
We will do more tests to check it.
- Redo the experiment and check the spot behind the window at high power.
- Move the power meter to the plane mirror M2 window. It was previously behind the curved mirror M4 window.
- Compare locking curves, cavity mode sizes, and coupling efficiency at different powers.
- After finishing the high-power experiments, we will measure the finesse using CW laser and the transmission of the mirrors used.
| Xinyi Lu wrote: |
|
Today, Ronic and I achieved 272kW inside the cavity at 7.5A. The coupling maintained 60%-70%.
| Amp current (A) |
Injection power (W) |
Circulating power (kW) |
Gain |
| 2 |
10 |
50 |
5000 |
| 3 |
22 |
105 |
4773 |
| 4 |
34 |
156 |
4588 |
| 5 |
47 |
210 |
4468 |
| 6 |
58(Estimated) |
250 |
4310 |
| 7.5 |
76(Estimated) |
272 |
3579 |
- Compared to yesterday's experiment, we moved the position of the D-shaped mirrors farther in two directions to make the higher-order modes just disappear.
- Possible reasons for higher gain: D-shaped mirrors position, high power and pump vacuum cleaned cavity mirrors so that improve the finesse.
- We didn't see the strange drops like yesterday (Figure 1). However, in the window behind the M3, we can see 3 spots correlating with the intracavity power, even though moving the D-shaped very far does not make them disappear, only weakens them. We don't know where they came from. When this round of experiments is over, we can open the cavity and observe the optical paths.
- Next steps:
- Repeat the experiment to ensure that the gain does not drop.
- Long-term measurement at maximum power when the amplifier temperature is safe.
- Measure the transmittance of the cavity mirrors and the amplifier power.
- Open the cavity and observe the optical paths and the mirror surface.
| Xinyi Lu wrote: |
|
all the injection power in the chart have not been measured recently but during the Loic thesis period.
and these old measurements stopped at 5.5A of pump current.... so, the data at "8A" is a pure estimation.
about the last measurement :
it was made at 6A/8A/8A/8A for the 4 pump diodes of the amplifier (because 1st stage has a Peltier issue and we cannot check its temperature), so the average current is 7.5A instead of 8A.
and the linear scale between pump current and amplifier power is ~ 12W/A, then the estimated amplifier power for the last measurement is 76W instead of 87W
and the estimated gain is more 2658.
for this current, the amplifier works out of its nominal limits (temperature set at 25°C but measured at 30°C !!!) and the fans of the crate are making noise like hell.
so the last gain estimation should be treated very cautiously.
about the transmission and reflection signals behavior, one can write :
R + T + L = 1 => energy conservation for the cavity.
dR + dT + dL = 0 => dL = - (dR + dT)
if dX = Xfinal - Xinitial, dR and dT are < 0 on the last picture, then dL > 0.
it means that this picture seems to show that some losses are increasing from the beginning of the locking process.
several possibilities :
- we saw a strange D-shape effect on the large port of the cavity.
it seems that one of the D-shape mount/mirror is touching the intra-cavity beam producing some ghost effect on this large cavity port.
some cavity axis changing during the beginning of the lock could introduce some additionnal losses.
it can be easily tested by puting the D-shapes far from the beam.
- because of cavity axis changing at the beginning of the lock, the mirror losses are different.
but it is surprising that it is still going in the same direction... more losses at the end.
could be tested by slightly changing the optical axis of the cavity.
- "prior damage" behavior with a bump in the middle of the mirror due to thermal effect which introduces some losses at the end.
=> if it's the case, it's not a good behavior !!! :-(((
can be tested by looking at the wavefront phase in transmission.
- Non linear effect is the coatings.
but the field density seems not so much to produce this kind of effect
- A thermally induced change in the refractive index of the mirrors.
Daniele mentionned a relation between real and imaginary (related to absorption) parts of this refractive index which could explain that a reflectivity change could induce an absorption change.
| Xinyi Lu wrote: |
|
These days, Ronic and I achieved 200kW inside the cavity and 70% coupling efficiency.
- By optimizing the telescope, the coupling reached 70% with iris fully open and maintained 60%-70% coupling at high power.
- The cavity mode went from 2.2mm,2.5mm (38kW) to finally 2.3mm,2.8mm (200kW) without changing a lot.
- Gradually raising the power while optimizing alignment, CEP, and locking, we got the following stable power:
| Amp current (A) |
Injection power (W) |
Circulating power (kW) |
Gain |
| 2 |
10 |
38 |
3800 |
| 2.3 |
14 |
50 |
3571 |
| 3 |
22 |
70 |
3181 |
| 4 |
35 |
115 |
3285 |
| 5 |
48 |
158 |
3292 |
| 8 |
87(Estimated) |
202 |
2322 |
- Next steps:
- Explain the strange drop phenomenon that occurs at high power, where both transmission and reflection drop, as in Fig. 2.
- Maintains a half-hour locking at 200kW. Now the temperature of the amplifier at 8A is over 40 degrees, which may be risky.
|
|
|
|
|
| Attachment 1: record.png
|  |
| Attachment 2: power_vs_time.png
|  |
| Attachment 3: cavitymode_vs_power.png
|  |
|
205
|
Wed Mar 27 22:37:02 2024 |
Xinyi Lu | Fixed | info | lasers and optics | Optical room | High power experiments (272kW) | Today, Ronic and I achieved 272kW inside the cavity at 7.5A. The coupling maintained 60%-70%.
| Amp current (A) |
Injection power (W) |
Circulating power (kW) |
Gain |
| 2 |
10 |
50 |
5000 |
| 3 |
22 |
105 |
4773 |
| 4 |
34 |
156 |
4588 |
| 5 |
47 |
210 |
4468 |
| 6 |
58(Estimated) |
250 |
4310 |
| 7.5 |
76(Estimated) |
272 |
3579 |
- Compared to yesterday's experiment, we moved the position of the D-shaped mirrors farther in two directions to make the higher-order modes just disappear.
- Possible reasons for higher gain: D-shaped mirrors position, high power and pump vacuum cleaned cavity mirrors so that improve the finesse.
- We didn't see the strange drops like yesterday (Figure 1). However, in the window behind the M3, we can see 3 spots correlating with the intracavity power, even though moving the D-shaped very far does not make them disappear, only weakens them. We don't know where they came from. When this round of experiments is over, we can open the cavity and observe the optical paths.
- Next steps:
- Repeat the experiment to ensure that the gain does not drop.
- Long-term measurement at maximum power when the amplifier temperature is safe.
- Measure the transmittance of the cavity mirrors and the amplifier power.
- Open the cavity and observe the optical paths and the mirror surface.
| Xinyi Lu wrote: |
|
all the injection power in the chart have not been measured recently but during the Loic thesis period.
and these old measurements stopped at 5.5A of pump current.... so, the data at "8A" is a pure estimation.
about the last measurement :
it was made at 6A/8A/8A/8A for the 4 pump diodes of the amplifier (because 1st stage has a Peltier issue and we cannot check its temperature), so the average current is 7.5A instead of 8A.
and the linear scale between pump current and amplifier power is ~ 12W/A, then the estimated amplifier power for the last measurement is 76W instead of 87W
and the estimated gain is more 2658.
for this current, the amplifier works out of its nominal limits (temperature set at 25°C but measured at 30°C !!!) and the fans of the crate are making noise like hell.
so the last gain estimation should be treated very cautiously.
about the transmission and reflection signals behavior, one can write :
R + T + L = 1 => energy conservation for the cavity.
dR + dT + dL = 0 => dL = - (dR + dT)
if dX = Xfinal - Xinitial, dR and dT are < 0 on the last picture, then dL > 0.
it means that this picture seems to show that some losses are increasing from the beginning of the locking process.
several possibilities :
- we saw a strange D-shape effect on the large port of the cavity.
it seems that one of the D-shape mount/mirror is touching the intra-cavity beam producing some ghost effect on this large cavity port.
some cavity axis changing during the beginning of the lock could introduce some additionnal losses.
it can be easily tested by puting the D-shapes far from the beam.
- because of cavity axis changing at the beginning of the lock, the mirror losses are different.
but it is surprising that it is still going in the same direction... more losses at the end.
could be tested by slightly changing the optical axis of the cavity.
- "prior damage" behavior with a bump in the middle of the mirror due to thermal effect which introduces some losses at the end.
=> if it's the case, it's not a good behavior !!! :-(((
can be tested by looking at the wavefront phase in transmission.
- Non linear effect is the coatings.
but the field density seems not so much to produce this kind of effect
- A thermally induced change in the refractive index of the mirrors.
Daniele mentionned a relation between real and imaginary (related to absorption) parts of this refractive index which could explain that a reflectivity change could induce an absorption change.
| Xinyi Lu wrote: |
|
These days, Ronic and I achieved 200kW inside the cavity and 70% coupling efficiency.
- By optimizing the telescope, the coupling reached 70% with iris fully open and maintained 60%-70% coupling at high power.
- The cavity mode went from 2.2mm,2.5mm (38kW) to finally 2.3mm,2.8mm (200kW) without changing a lot.
- Gradually raising the power while optimizing alignment, CEP, and locking, we got the following stable power:
| Amp current (A) |
Injection power (W) |
Circulating power (kW) |
Gain |
| 2 |
10 |
38 |
3800 |
| 2.3 |
14 |
50 |
3571 |
| 3 |
22 |
70 |
3181 |
| 4 |
35 |
115 |
3285 |
| 5 |
48 |
158 |
3292 |
| 8 |
87(Estimated) |
202 |
2322 |
- Next steps:
- Explain the strange drop phenomenon that occurs at high power, where both transmission and reflection drop, as in Fig. 2.
- Maintains a half-hour locking at 200kW. Now the temperature of the amplifier at 8A is over 40 degrees, which may be risky.
|
|
|
| Attachment 1: Screenshot_2024-03-27_7_270kW_7.5A.png
|  |
| Attachment 2: 210_kW_power_at_5A_injection.png
|  |
| Attachment 3: 272.3kW_at_7.5A.jpg
|  |
|
203
|
Tue Mar 26 19:36:48 2024 |
Xinyi Lu | Fixed | info | lasers and optics | Optical room | High power experiments (200kW) | These days, Ronic and I achieved 200kW inside the cavity and 70% coupling efficiency.
- By optimizing the telescope, the coupling reached 70% with iris fully open and maintained 60%-70% coupling at high power.
- The cavity mode went from 2.2mm,2.5mm (38kW) to finally 2.3mm,2.8mm (200kW) without changing a lot.
- Gradually raising the power while optimizing alignment, CEP, and locking, we got the following stable power:
| Amp current (A) |
Injection power (W) |
Circulating power (kW) |
Gain |
| 2 |
10 |
38 |
3800 |
| 2.3 |
14 |
50 |
3571 |
| 3 |
22 |
70 |
3181 |
| 4 |
35 |
115 |
3285 |
| 5 |
48 |
158 |
3292 |
| 8 |
87(Estimated) |
202 |
2322 |
- Next steps:
- Explain the strange drop phenomenon that occurs at high power, where both transmission and reflection drop, as in Fig. 2.
- Maintains a half-hour locking at 200kW. Now the temperature of the amplifier at 8A is over 40 degrees, which may be risky.
|
| Attachment 1: 202kW_power_at_8A_injection.png
|  |
| Attachment 2: Strange_drops.jpg
|  |
|
204
|
Wed Mar 27 09:47:37 2024 |
Xinyi Lu | Fixed | info | lasers and optics | Optical room | High power experiments (200kW) | all the injection power in the chart have not been measured recently but during the Loic thesis period.
and these old measurements stopped at 5.5A of pump current.... so, the data at "8A" is a pure estimation.
about the last measurement :
it was made at 6A/8A/8A/8A for the 4 pump diodes of the amplifier (because 1st stage has a Peltier issue and we cannot check its temperature), so the average current is 7.5A instead of 8A.
and the linear scale between pump current and amplifier power is ~ 12W/A, then the estimated amplifier power for the last measurement is 76W instead of 87W
and the estimated gain is more 2658.
for this current, the amplifier works out of its nominal limits (temperature set at 25°C but measured at 30°C !!!) and the fans of the crate are making noise like hell.
so the last gain estimation should be treated very cautiously.
about the transmission and reflection signals behavior, one can write :
R + T + L = 1 => energy conservation for the cavity.
dR + dT + dL = 0 => dL = - (dR + dT)
if dX = Xfinal - Xinitial, dR and dT are < 0 on the last picture, then dL > 0.
it means that this picture seems to show that some losses are increasing from the beginning of the locking process.
several possibilities :
- we saw a strange D-shape effect on the large port of the cavity.
it seems that one of the D-shape mount/mirror is touching the intra-cavity beam producing some ghost effect on this large cavity port.
some cavity axis changing during the beginning of the lock could introduce some additionnal losses.
it can be easily tested by puting the D-shapes far from the beam.
- because of cavity axis changing at the beginning of the lock, the mirror losses are different.
but it is surprising that it is still going in the same direction... more losses at the end.
could be tested by slightly changing the optical axis of the cavity.
- "prior damage" behavior with a bump in the middle of the mirror due to thermal effect which introduces some losses at the end.
=> if it's the case, it's not a good behavior !!! :-(((
can be tested by looking at the wavefront phase in transmission.
- Non linear effect is the coatings.
but the field density seems not so much to produce this kind of effect
- A thermally induced change in the refractive index of the mirrors.
Daniele mentionned a relation between real and imaginary (related to absorption) parts of this refractive index which could explain that a reflectivity change could induce an absorption change.
| Xinyi Lu wrote: |
|
These days, Ronic and I achieved 200kW inside the cavity and 70% coupling efficiency.
- By optimizing the telescope, the coupling reached 70% with iris fully open and maintained 60%-70% coupling at high power.
- The cavity mode went from 2.2mm,2.5mm (38kW) to finally 2.3mm,2.8mm (200kW) without changing a lot.
- Gradually raising the power while optimizing alignment, CEP, and locking, we got the following stable power:
| Amp current (A) |
Injection power (W) |
Circulating power (kW) |
Gain |
| 2 |
10 |
38 |
3800 |
| 2.3 |
14 |
50 |
3571 |
| 3 |
22 |
70 |
3181 |
| 4 |
35 |
115 |
3285 |
| 5 |
48 |
158 |
3292 |
| 8 |
87(Estimated) |
202 |
2322 |
- Next steps:
- Explain the strange drop phenomenon that occurs at high power, where both transmission and reflection drop, as in Fig. 2.
- Maintains a half-hour locking at 200kW. Now the temperature of the amplifier at 8A is over 40 degrees, which may be risky.
|
|
|
52
|
Wed Jan 29 19:00:02 2020 |
Loïc Amoudry | Fixed | report | lasers and optics | Optical room | Glow discharge cleaner on SBOX mirrors | The glow discharge cleaner has been tested on the SBOX mirrors.
I've put them 1 by 1. Each run was 15min long at 15mA. The mirrors HR face was always away from the electrode and ~35° angle with the support. These values have been choosen thanks to the reference:
We have learned that Air can be compared to Azote and Azote to Oxygen in glow discharge. The main difference is H2O in air which make the glow discharge less stable as say several papers.
|
| Attachment 1: glow.PNG
|  |
|
91
|
Tue May 24 22:11:40 2022 |
Manar Amer | Fixed | report | lasers and optics | Optical room | Fundamental Mode TEM00 | The current setup for the SBox has a beam viewer and 2 photodiodes placed at reflection and transmission.
The CW laser piezoelectric crystal was driven using the lase lock system to observe the 00 mode.
Mode Observed and has no reflection (from what was previously seen)
higher order modes are resonating with 00 mode , example 11 mode (shown in image attached)
the coupling is yet to be seen and measured. |
| Attachment 1: 20220524_SBox_Setup.png
|  |
| Attachment 2: 00mode_CW_piezo_drive.bmp
|
| Attachment 3: 00mode_11mode.bmp
|
|
92
|
Wed May 25 17:34:29 2022 |
Manar Amer | Fixed | report | lasers and optics | Optical room | Fundamental Mode TEM00 | Adding images from the transmission after the spherical mirrors M3 and M4 window for a resonating mode inside the cavity.
There appears to be some misalignment from the center of the mirror ???
| Manar Amer wrote: |
|
The current setup for the SBox has a beam viewer and 2 photodiodes placed at reflection and transmission.
The CW laser piezoelectric crystal was driven using the lase lock system to observe the 00 mode.
Mode Observed and has no reflection (from what was previously seen)
higher order modes are resonating with 00 mode , example 11 mode (shown in image attached)
the coupling is yet to be seen and measured.
|
|
| Attachment 1: beamviwer_transmission_at_M3.bmp
|
| Attachment 2: beamviwer_transmission_at_M4.bmp
|
|
94
|
Wed Jun 8 10:58:15 2022 |
Manar Amer | Fixed | report | lasers and optics | Optical room | Fundamental Mode TEM00 | Images of the Transmitted beam at M2 mirror at different days.
The first one was from last week, the second from yesterday.
There is misalignment (drift due to temperature) from the position where the beam was initially. ( reference taken between centers of mode and direct injected beam)
it is most clear in the vertical position.
| Manar Amer wrote: |
|
Adding images from the transmission after the spherical mirrors M3 and M4 window for a resonating mode inside the cavity.
There appears to be some misalignment from the center of the mirror ???
| Manar Amer wrote: |
|
The current setup for the SBox has a beam viewer and 2 photodiodes placed at reflection and transmission.
The CW laser piezoelectric crystal was driven using the lase lock system to observe the 00 mode.
Mode Observed and has no reflection (from what was previously seen)
higher order modes are resonating with 00 mode , example 11 mode (shown in image attached)
the coupling is yet to be seen and measured.
|
|
|
| Attachment 1: 20220530_00_Mode.bmp
|
| Attachment 2: 00_Mode_Beam_Transmitted_Position_drift_due_to_temperature.bmp
|
|
102
|
Wed Jul 6 18:35:38 2022 |
Manar Amer | Fixed | report | lasers and optics | Optical room | Fundamental Mode TEM00 | Closing series of 00 mode for FSR @ 133.33 MHz
| Manar Amer wrote: |
|
Images of the Transmitted beam at M2 mirror at different days.
The first one was from last week, the second from yesterday.
There is misalignment (drift due to temperature) from the position where the beam was initially. ( reference taken between centers of mode and direct injected beam)
it is most clear in the vertical position.
| Manar Amer wrote: |
|
Adding images from the transmission after the spherical mirrors M3 and M4 window for a resonating mode inside the cavity.
There appears to be some misalignment from the center of the mirror ???
| Manar Amer wrote: |
|
The current setup for the SBox has a beam viewer and 2 photodiodes placed at reflection and transmission.
The CW laser piezoelectric crystal was driven using the lase lock system to observe the 00 mode.
Mode Observed and has no reflection (from what was previously seen)
higher order modes are resonating with 00 mode , example 11 mode (shown in image attached)
the coupling is yet to be seen and measured.
|
|
|
|
|
22
|
Mon Nov 5 13:11:08 2018 |
Loïc Amoudry | Fixed | report | lasers and optics | Optical room | First run with spare mirrors |
| I (A) |
Trans (mW) |
Coupling (%) |
Pin (W) |
Gain |
| 0 |
4 |
70 |
0.37 |
4982 |
| 2 |
58 |
80 |
5.2 |
5140 |
| 4 |
180 |
75 |
16.1 |
5152 |
| 6 |
270 |
63 |
27.3 |
4558 |
| 8 |
340 |
60 |
36.7 |
4269 |
|
| Attachment 1: Plot_power_and_gain_vs_all.JPG
|  |
| Attachment 2: powerup.xlsx
|
|
12
|
Wed Oct 31 11:36:30 2018 |
Loïc Amoudry | Fixed | report | lasers and optics | Optical room | Finesse vs power by difference between main and second resonance | Measurements show that ratio decrease versus power. BUT, the second resonance measurement induce lower power in the cavity so the ratio is not directly true.
Also, simulation of the main/second resonance power by Pierre's simulation has shown ratio ~50, ~47.6 and 43.5 respectively for 0A, 2A and 4A.
| I (A) |
Main resonance (mW) |
Second resonance (mW) |
Ratio |
| 0 |
8.07 |
0.416 |
19.4 |
| 2 |
121 |
6.77 |
17.9 |
| 4 |
324 |
20.2 |
16 |
|
| Attachment 1: CrossSecondaryResonance.m
|
clear all; close all;
tic
addpath(genpath('C:\Users\amoudry\desktop\Fichiers Labo\Fichiers Pierre\Simulation\Personal codes\Various'))
[TAS,~,r] = GetCavity('SBOX_ULE');
[F,~] = Get_info(TAS(1:4),TAS(5:8),TAS(9:12));
lambda = 1030e-9;
c = 299792458;
FSR = 133.33e6;
w0 = 2*pi*c/lambda;
tau = 1e-12; % FWHM duration
a = 4*log(2)/tau^2;
E0 = 1;%(pi/2/a)^(1/2); % Energy to normalize gaussian spectrum (Input beam power = 1)
DeltaPhiCE = 0; % CEP
N = 1e5;
dk = 0:(N-1);
Aa = (r.^dk-r.^(2.*N-dk));
Bb = E0*TAS(1)./(1-r.^2);
Cc = (1-r.^(2.*N));
Nn = 5e2; % Increase Nn <-> increase resolution
dtt = -Nn:Nn;
dtt = dtt*lambda/c/(0.1*Nn); %1e6
Ecn = zeros(numel(dtt),1);
for ii = 1:numel(dtt)
for ll = 0:3
% ll = 0;
dt = dtt(ii)+ll*lambda/c;
Phid = DeltaPhiCE + w0.*dt;
temp_vect = Aa.*cos(dk.*Phid).*exp(-a.*dk.^2.*dt.^2./2);
Ecn(ii,ll+1) = Bb.*(2*sum(temp_vect)-Cc);
disp([num2str(ii)]);
end
end
toc
%% Time plots
% figure
% semilogy(dtt/lambda*c,Ecn/max(Ecn),'LineWidth',2)
% hold on
% semilogy(dtt/lambda*c,Ecn2/max(Ecn),'LineWidth',2)
% hold on
% semilogy(dtt/lambda*c,Ecn3/max(Ecn),'LineWidth',2)
% hold on
% semilogy(dtt/lambda*c,Ecn4/max(Ecn),'LineWidth',2)
% set(gca,'FontSize',15)
% xlabel('\DeltaT (\lambda/c)')
% ylabel('Energy (A.U.)')
% grid on
% legend('\DeltaT = 0','\DeltaT = \lambda/c','\DeltaT = 2\lambda/c','\DeltaT = 3\lambda/c')
% axis square
% figure
% semilogy(dtt/lambda*c,Ecn/max(Ecn),'LineWidth',2)
% grid on
% set(gca,'FontSize',25)
% % set(gca,'YLim',[1e-9 1e0])
% xlabel('\DeltaT (\lambda_0/c)')
% ylabel('log(Energie (u.a.))')
%% Frequency
nu0 = w0/2/pi;
frep = (1/FSR-nu0/FSR*dtt).^(-1); % Infinity in dtt = 1/nu0
fprintf('\nFinesse : %g\n\n',F);
% Get linewidth
figure
for jj = 1:4
% Find the 2 minimas of Ecn_half. Take the corresponding frep and
% substract them
Ecn_half = abs(Ecn(:,jj)-max(Ecn(:,jj))/2);
Ecn_half2 = sort(Ecn_half);
[row1,~] = find(Ecn_half==Ecn_half2(1),1);
[row2,~] = find(Ecn_half==Ecn_half2(2),2);
if numel(row2)>1 % Sometimes row can be a vector
row2 = row2(2);
end
dnu = abs(frep(row2)-frep(row1));
fprintf('RES %g\nMax gain : %g. Linewidth : %g kHz\n\n',jj-1,max(Ecn(:,jj)),dnu/1e3);
% plot((frep-FSR)/FSR,Ecn(:,jj)/max(Ecn(:,1)),'LineWidth',2)
% hold on
semilogy((frep-FSR)/FSR,Ecn(:,jj)/max(Ecn(:,1)),'LineWidth',2)
xlim([-0.05 0.05])
hold on
end
set(gca,'FontSize',15)
xlabel('(f_r_e_p-FSR)/FSR')
% ylabel('Energy (A.U.)')
ylabel('log(Energie (u.a.))')
grid on
legend('\DeltaT = 0','\DeltaT = \lambda/c','\DeltaT = 2\lambda/c','\DeltaT = 3\lambda/c')
axis square
% axis([-0.01 0.01 10^-6 1])
|
| Attachment 2: GetCavity.m
|
function [TAS,r,r_prod] = GetCavity(cav_name,varargin)
% Return T and r coefficient of a given cavity
% TAS vector contains the 4 T coeffs, then 4 A coeffs, then 4 S coeffs
if strcmp(cav_name,'SBOX_ULE')==1
TAS(1) = 180e-6; % T
TAS(2) = 2e-6;
TAS(3) = 2e-6;
TAS(4) = 2e-6;
TAS(5) = 1.15e-6; % A
TAS(6) = 1.27e-6;
TAS(7) = 1.2e-6;
TAS(8) = 1e-6;
TAS(9) = 7e-6; % S
TAS(10) = 4.5e-6;
TAS(11) = 3.6e-6;
TAS(12) = 9e-6;
% TAS(1) = 180e-6; % T
% TAS(2) = 3.2e-6;
% TAS(3) = 2.8e-6;
% TAS(4) = 2.85e-6;
% TAS(5) = 30e-6; % A
% TAS(6) = 30e-6;
% TAS(7) = 30e-6;
% TAS(8) = 30e-6;
% TAS(9) = 20e-6; % S
% TAS(10) = 20e-6;
% TAS(11) = 20e-6;
% TAS(12) = 20e-6;
elseif strcmp(cav_name,'ThomX')==1
TAS(1) = 120e-6; % T
TAS(2) = 1.5e-6;
TAS(3) = 1.5e-6;
TAS(4) = 1.5e-6;
TAS(5) = 0.4e-6; % A
TAS(6) = 0.24e-6;
TAS(7) = 0.24e-6;
TAS(8) = 0.27e-6;
TAS(9) = 4e-6; % S
TAS(10) = 4.5e-6;
TAS(11) = 10e-6;
TAS(12) = 4.5e-6;
elseif strcmp(cav_name,'MIGHTY_low')==1
TAS(1) = 1060e-6;
TAS(2) = 330e-6;
TAS(3) = 330e-6;
TAS(4) = 330e-6;
TAS(5:12) = 0;
elseif strcmp(cav_name,'Fab_cav')==1
TAS(1) = 100e-6;
TAS(2) = 10e-6;
TAS(3) = 10e-6;
TAS(4) = 10e-6;
TAS(5:12) = 0;
end
switch nargin
case 2
TAS = repmat(TAS,numel(varargin{1}),1);
TAS(:,1) = varargin{1};
case 3
TAS = repmat(TAS,numel(varargin{1}),1);
TAS(:,1) = varargin{1};
TAS(:,2) = varargin{2};
end
% Field reflection coeffs
rr = @(TAS) (1-sum(TAS,2)).^(1/2);
for ii = 1:4
r(:,ii) = rr(TAS(:,ii:4:12));
end
r_prod = prod(r,2);
end
|
|
15
|
Wed Oct 31 13:43:28 2018 |
Loïc Amoudry | Fixed | report | lasers and optics | Optical room | Finesse vs power by difference between main and second resonance | Measurement on 24/10/18
| Loïc Amoudry wrote: |
|
Measurements show that ratio decrease versus power. BUT, the second resonance measurement induce lower power in the cavity so the ratio is not directly true.
Also, simulation of the main/second resonance power by Pierre's simulation has shown ratio ~50, ~47.6 and 43.5 respectively for 0A, 2A and 4A.
| I (A) |
Main resonance (mW) |
Second resonance (mW) |
Ratio |
| 0 |
8.07 |
0.416 |
19.4 |
| 2 |
121 |
6.77 |
17.9 |
| 4 |
324 |
20.2 |
16 |
|
|
|
16
|
Wed Oct 31 13:44:22 2018 |
Loïc Amoudry | Fixed | report | lasers and optics | Optical room | Finesse vs power by difference between main and second resonance | Measurement on 25/10/2018
| Loïc Amoudry wrote: |
|
Measurements show that ratio decrease versus power. BUT, the second resonance measurement induce lower power in the cavity so the ratio is not directly true.
Also, simulation of the main/second resonance power by Pierre's simulation has shown ratio ~50, ~47.6 and 43.5 respectively for 0A, 2A and 4A.
| I (A) |
Main resonance (mW) |
Second resonance (mW) |
Ratio |
| 0 |
8.07 |
0.416 |
19.4 |
| 2 |
121 |
6.77 |
17.9 |
| 4 |
324 |
20.2 |
16 |
|
|
|
217
|
Mon Apr 15 18:19:40 2024 |
Xinyi Lu | Fixed | info | lasers and optics | Optical room | Finesse measurement of 2-mirror cavity | - Today Daniele and I cleaned the spherical mirror by wiping it with alcohol, and the finesse increased to 47k in air.
- After vacuuming, the final finesse is about 45k. The enhancement factor is expected to be 23k.
- Then we tuned the cavity length, FSR = 216.666 MHz. Aurélien helped us to install the menhir laser of 216 MHz.
- Tomorrow we will optimize the optical path and inject the laser into the fiber.
| Xinyi Lu wrote: |
|
Today Viktor and I completed the installation of the two-mirror cavity and managed to lock and measure the finesse.
- The finesse is 36k now (see figure 1). For the designed value of the mirror, the expected finesse is ~50k.
- The diameter of M2 transmission is 1.67 mm,1.65 mm (see figure 2).
- The installation process took a lot of time in orienting the PBS. In addition, we found that the cavity reflected beam and the window reflected beam would interfere (see figure 3). The small spot in the lower right corner is the window reflected light.
- We need to discuss whether the next step is to clean the mirrors or vacuum and move on.
| Xinyi Lu wrote: |
|
Today, Viktor and I started installing the two-mirror cavity.
- Firstly, we cleaned the environment and the dust counter showed good cleanliness
- After opening the cavity we tried to determine the source of the strange spot with a laser detection card and found that the beam was very close to the front edge of the longitudinal D-shaped mirror. In addition there was nothing else strange.
- The setup of the two-mirror cavity is shown in Figure 1. We have to use the menhir laser of 216MHz. The mirrors used are shown in Figure 2.
- We have installed the M2 and will continue the installation tomorrow.
|
|
|
| Attachment 1: finesse_45k.png
|  |
|
214
|
Wed Apr 10 11:35:54 2024 |
Xinyi Lu | Fixed | info | lasers and optics | Optical room | Finesse measurement (35k) | These days, Ronic, Aurélien and I use OEwaves CW laser to measure the finesse of SBOX. We made 5 measurements at 100kHz / 4s sweeps.
The finesse is around 35k (see Figure 1), corresponding to an enhancement factor of 14k.
In our experiments, we only saw up to 9k gain with 70% coupling, corresponding to an enhancement factor of 12.8k.
It could be because of the additional losses introduced by the high power, or the mirror became cleaner after the experiment......
Additionally, we found that the output of the OEwaves CW laser was not a perfect circle, with a depression at the edge of the circle. |
| Attachment 1: 5_measurements_of_finesse.png
|  |
| Attachment 2: fit.png
|  |
|
242
|
Thu Sep 4 17:52:03 2025 |
Alice Renaux | Under Process | report | lasers and optics | Optical room | Finesse measurement | Today, with Ronic, we measured the finesse of the 2-mirror cavity witht the NKT CW laser.
We were able to perfrom the measurement only once, and the results of the measurement are attached to this note. We added sidebands to the laser spectrum peak thanks to an EOM, and we sweeped the modulation frequency on a 1MHz span around an estimated FSR of 216.63MHz in 10s. We found a 82kHz linewidth, hence a finesse of 2651. |
| Attachment 1: Figure_3.png
|  |
|
243
|
Thu Sep 4 17:56:50 2025 |
Alice Renaux | Under Process | report | lasers and optics | Optical room | Finesse measurement | (Finesse 2651 is consistent with that obtained from the mirrors' transmission coefficients, which is about 3100.)
| Alice Renaux wrote: |
|
Today, with Ronic, we measured the finesse of the 2-mirror cavity witht the NKT CW laser.
We were able to perfrom the measurement only once, and the results of the measurement are attached to this note. We added sidebands to the laser spectrum peak thanks to an EOM, and we sweeped the modulation frequency on a 1MHz span around an estimated FSR of 216.63MHz in 10s. We found a 82kHz linewidth, hence a finesse of 2651.
|
|
|
218
|
Tue Apr 16 18:38:04 2024 |
Xinyi Lu | Fixed | info | lasers and optics | Optical room | Fiber injection, spectrum and connection of 2nd stage amplifier | Today, Daniele and I injected the laser into the fiber, installed the telescope, connected the second stage of the amplifier, and obtained resonances.
- The output power of the menhir laser @ 216MHz is 150mW, after CVBG is 28mW , 9.6mW injected into the fiber, and 1.6mW via AOM and EOM. This is not far from the minimum 1mW seed power required by the amplifier.
- The spectrum after CVBG is shown in Figure 1.
- The waist of this 2-mirror cavity is 0.583 mm, and the position is on the M1. A set of telescopes is designed and installed as in Figure 2.
- We injected the second stage of the amplifier into the cavity and obtained fundamental mode. Aurélien and I are trying to lock it. |
| Attachment 1: CVBG_inject_to_fiber.png
|  |
| Attachment 2: telescope.png
|  |
|
111
|
Tue Jul 12 10:07:05 2022 |
Manar Amer | Fixed | report | lasers and optics | detectors and electronics | Optical room | FSR change & Finesse Measurements | The FSR of the 2 mirror (plan-spherical) Cavity was adjusted from 210 MHz to reach 216.643 MHz
it was done by having two reference irises, one at the injection point and one at the reflection
then changing the position of injection plan mirror to slightly closer distance and monitoring the reflection on the oscilloscope to be max.
The cavity modes were still seen, and we had to only improve the injection alignment after.
Me and Ronic locked in air and measured the Finesse, which was bigger by ~ 20%
average Finesse = 30208.53614
FWHM (KHz) = 7.0179
Finesse = 30869.9522
FWHM (KHz) = 7.1257
Finesse = 30403.005
FWHM (KHz) = 7.1287
Finesse = 30390.4014
FWHM (KHz) = 7.2884
Finesse = 29724.5531
FWHM (KHz) = 7.3055
Finesse = 29654.769
| Manar Amer wrote: |
|
Update for Finesse measurement, The cavity was put under vacuum ~ 1.1*10^-1 mbar
and the alignment and coupling improved.
FSR = 210.1 MHz
Average Finesse = 25686.46222
FWHM (KHz) = 8.2387
Finesse = 25501.5659
FWHM (KHz) = 8.2028
Finesse = 25613.2858
FWHM (KHz) = 8.0978
Finesse = 25945.3289
FWHM (KHz) = 8.1744
Finesse = 25702.3142
FWHM (KHz) = 8.1847
Finesse = 25669.8163
Concluded from Ronic's calculations, this could be the maximum finesse we might be able to obtain with this setup
with Gain ~ 8000
On Monday we adjust the frequency to match 2160.66 MHz and lock the Pulsed,
at the same time start we start with the CELIA amplifier.
| Manar Amer wrote: |
|
The cavity was realigned using irises instead of pinholes, gave a better alignment.
The inside of the box, the spherical and the injection mirror were cleaned and placed back inside the box.
we see beating of fundamental mode, previously at the transmission point we placed a wedge to split the beam which resulted in an elliptical mode
we removed it and placed a very thin beam splitter, the beam is circular now.
The cavity was locked in air at a coupling of ~ 60-70 %
Finesse and line width measured five readings with a Finesse average 25095.08884 of a Gain ~ 8000
FWHM (KHz) = 8.2928
Finesse = 25323.0544
FWHM (KHz) = 7.9202
Finesse = 26514.4395
FWHM (KHz) = 8.5834
Finesse = 24465.8636
FWHM (KHz) = 8.4571
Finesse = 24831.2419
FWHM (KHz) = 8.6275
Finesse = 24340.8448
Theoretical and expected Finesse for the 2 mirror setup with the losses is calculated by Ronic for comparison between four and 2 mirror setup.
| Manar Amer wrote: |
|
The SBox cavity setup was changed to have only 2 mirrors M1 plane and M2 spherical, both from ThomX
Distance between the mirror ~ 72 cm , increased from 70 cm to take into account the thickness of the ThomX mirrors
Two lenses (300 mm @ 50 cm , 200 @ 104 cm) were placed to have the beam radius ~ 0.55 mm.
The cavity was locked with a coupling of 60 %, for Finesse measurement the sweep was taken over 100 KHz of 2 seconds.
FSR ~ 210.00 MHz, line width ~ 8.56 KHz, Finesse ~ 24 500 .
|
|
|
|
| Attachment 1: 00mode.jpg
|  |
| Attachment 2: 00mode_diameter.jpg
|  |
| Attachment 3: 00mode_diameter_fit.jpg
|  |
|
112
|
Tue Jul 12 10:19:30 2022 |
Manar Amer | Fixed | report | lasers and optics | detectors and electronics | Optical room | FSR change & Finesse Measurements | Yesterday evening the cavity was Vacuum pumped up to pressure of 5.5*10^-2 and locked
changed FSR to be 216.662 MHz and alignment a little and measured the Finesse
in Vacuum we have average Finesse = 30341.6265
FWHM (KHz) = 7.0592
Finesse = 30692.1961
FWHM (KHz) = 7.2186
Finesse = 30014.556
FWHM (KHz) = 7.1051
Finesse = 30493.7635
FWHM (KHz) = 7.1079
Finesse = 30481.9812
FWHM (KHz) = 7.1413
Finesse = 30339.2695
FWHM (KHz) = 7.1624
Finesse = 30249.776
FWHM (KHz) = 7.0239
Finesse = 30846.2719
FWHM (KHz) = 7.2614
Finesse = 29837.6477
FWHM (KHz) = 7.1935
Finesse = 30119.1768
| Manar Amer wrote: |
|
The FSR of the 2 mirror (plan-spherical) Cavity was adjusted from 210 MHz to reach 216.643 MHz
it was done by having two reference irises, one at the injection point and one at the reflection
then changing the position of injection plan mirror to slightly closer distance and monitoring the reflection on the oscilloscope to be max.
The cavity modes were still seen, and we had to only improve the injection alignment after.
Me and Ronic locked in air and measured the Finesse, which was bigger by ~ 20%
average Finesse = 30208.53614
FWHM (KHz) = 7.0179
Finesse = 30869.9522
FWHM (KHz) = 7.1257
Finesse = 30403.005
FWHM (KHz) = 7.1287
Finesse = 30390.4014
FWHM (KHz) = 7.2884
Finesse = 29724.5531
FWHM (KHz) = 7.3055
Finesse = 29654.769
| Manar Amer wrote: |
|
Update for Finesse measurement, The cavity was put under vacuum ~ 1.1*10^-1 mbar
and the alignment and coupling improved.
FSR = 210.1 MHz
Average Finesse = 25686.46222
FWHM (KHz) = 8.2387
Finesse = 25501.5659
FWHM (KHz) = 8.2028
Finesse = 25613.2858
FWHM (KHz) = 8.0978
Finesse = 25945.3289
FWHM (KHz) = 8.1744
Finesse = 25702.3142
FWHM (KHz) = 8.1847
Finesse = 25669.8163
Concluded from Ronic's calculations, this could be the maximum finesse we might be able to obtain with this setup
with Gain ~ 8000
On Monday we adjust the frequency to match 2160.66 MHz and lock the Pulsed,
at the same time start we start with the CELIA amplifier.
| Manar Amer wrote: |
|
The cavity was realigned using irises instead of pinholes, gave a better alignment.
The inside of the box, the spherical and the injection mirror were cleaned and placed back inside the box.
we see beating of fundamental mode, previously at the transmission point we placed a wedge to split the beam which resulted in an elliptical mode
we removed it and placed a very thin beam splitter, the beam is circular now.
The cavity was locked in air at a coupling of ~ 60-70 %
Finesse and line width measured five readings with a Finesse average 25095.08884 of a Gain ~ 8000
FWHM (KHz) = 8.2928
Finesse = 25323.0544
FWHM (KHz) = 7.9202
Finesse = 26514.4395
FWHM (KHz) = 8.5834
Finesse = 24465.8636
FWHM (KHz) = 8.4571
Finesse = 24831.2419
FWHM (KHz) = 8.6275
Finesse = 24340.8448
Theoretical and expected Finesse for the 2 mirror setup with the losses is calculated by Ronic for comparison between four and 2 mirror setup.
| Manar Amer wrote: |
|
The SBox cavity setup was changed to have only 2 mirrors M1 plane and M2 spherical, both from ThomX
Distance between the mirror ~ 72 cm , increased from 70 cm to take into account the thickness of the ThomX mirrors
Two lenses (300 mm @ 50 cm , 200 @ 104 cm) were placed to have the beam radius ~ 0.55 mm.
The cavity was locked with a coupling of 60 %, for Finesse measurement the sweep was taken over 100 KHz of 2 seconds.
FSR ~ 210.00 MHz, line width ~ 8.56 KHz, Finesse ~ 24 500 .
|
|
|
|
|
| Attachment 1: Screenshot_2022-07-11_1_204143.png
|  |
| Attachment 2: Screenshot_2022-07-11_0_203646.png
|  |
|