| ID |
Date |
Author |
Status |
Type |
Category |
Location |
Title |
|
145
|
Wed Sep 7 18:57:20 2022 |
Manar Amer | Fixed | report | lasers and optics | Optical room | Telescope / amplifier output |
We increased the power of the amplifier up to 10 W to see if there is a change in the beam shape at the injection point or the transmission.
There was no change in the shape of both of them from the reading at 1 W (with only the 2nd stage on)
Only saw an increase in the transmission power, which is expected.
| Manar Amer wrote: |
|
Am adjustment on the lenses position to have a smaller waist.
+ 250 mm @ 88 cm from amplifier
-150 mm @ 111 cm from amplifier
the overlap with this placement is ~ 91%
the measured beam FWHM at the injection point M1 estimated to be ~ 0.94 mm
waist = 0.85*0.94 = 0.79 mm , it is still much larger than the needed 0.58 mm radius waist.
There is an improvement in reducing higher order modes, but the fundamental is still too weak to see, we observe higher order even modes 11 , 44 , ...
| Manar Amer wrote: |
|
Note the correct beam divergence is approximately ~ 2.3 mrad
M2 = 1.1 in this fit, but it is not yet optimized !!!!! could be reason for not accurate telescope reading.
Have tInstalled a new telescope with lenses
250 mm @ 86.8 cm from amplifier ,
-150 mm @109 cm (~ 22 cm between lenses)
the beam waist measured at a point on the reflection which is relatively the same distance to the injection mirror and the beam was much smaller than before
@ ~ 2 meters from amplifier + telescope , FWHM = 1.2 mm , waist = 0.85 * FWHM = 1.02 mm
| Manar Amer wrote: |
|
Here is a view of beam propagation in the optical software : GaussianBeam
the red filled shape is the model of the CELIA amplifier beam propagation with a divergence of 4.46 mrad
(the 2 black dots is the measurement of the beam size without any lens to change the beam propagation).
the 2 black lines have been put at the input and output cavity mirrors position relative to the CELIA amplifier position, respectively 2m and 2.7m roughly.
the cavity mode radius should be 0.55mm and 0.7mm respectively.
the cavity mode shape is represented by the 2 red lines (very close to the red filled shape which is the beam).
the most simple working telescope could be a +250 lens at 280mm from the CELIA amplifier.
it gives a beam radius of 0.53mm at the input mirror and 0.64mm at the output mirror.
the overlapping is more than 99%
the 2nd file is the GaussianBeam file.
| Manar Amer wrote: |
|
I placed a periscope to adjust the high of the beam from the amplifier output from ~ 10 cm from the table to ~ 15 cm
a dichroic mirror placed after it to reject the pump laser, all the mirrors on the path to the cavity were replaced with dielectric mirrors BB01-E03
the length of the path from the amplifier output to the cavity coupling mirror ~ 2 meters
setup defines the different optics placed in the path
Note: the beam goes all the way to the cavity, put it is not yet optimized to the irises.
| Manar Amer wrote: |
|
Beam divergence was measured using a method called "Focal Length Divergence Measurement Method"
Where a lens of a known focal length is placed on the beam path and the beam waist is measured at the focal distance using a beam profiler.
We ramped the power up to 10 W
for a focal length = 400 mm,
we measured a FWHM = 2.1 mm,
corresponding to a divergence = 4.45 mrad (edit : wrong software use)
for comparison, we measured the FWHM 8.1 mm @ 1.55 m and extracted the divergence directly 4.46 mrad (edit : this measurement is wrong - wrong use of the software)
Note: better to use a lens of a focal lens higher than 100 mm (to reduce the error in the distance measured)
| Manar Amer wrote: |
|
The previous Sbox telescope was dismantled and the mechanical components cleaned.
its lenses are still in the mounts, it looks that two of them are spherical and two are cylindrical
2 are -100 mm and 2 are +150 mm, there is also a box containing fused silica lenses that could be used.
Note: at high power use only fused silica lenses not BK7 type
|
|
|
|
|
|
|
|
144
|
Tue Sep 6 17:47:40 2022 |
Ronic Chiche | Fixed | issue | lasers and optics | Optical room | unsuccessful telescope design :-( |
we wanted to calculate the right telescope with 2 spherical lenses.
1) we have the FP cavity mode size which is 0.58mm at the input mirror and 0.7mm at the output mirror.
2) we planned to measure the laser beam at the output of the amplifier working at P=1W (2nd stage ON only).
we did several measurements at different positions from the amplifier output.
for each of these measurements, we were able to fit the intensity profile I = I0 * exp(-2 *r^2 / w^2) on x or y axis, then we have w(z).
attached files give an example of the beam image at z=40mm and an example of the beam fits for w and y.
with all the w(z) measurements, we were able to fit the divergence of the beam => 2.3 mrad
attached file show the radius measurements and the divergence fit.
with this divergence, we should find a waist bigger than 140 µm (value for M²=1).
unfortunately the smallest beam radius measured is 116 µm which would give a M²<1 that is not allowed !
then it seems the measurements have not been done correctly... :-(
we will try to do them again... maybe at P=10W or 50W ?!? |
| Attachment 1: image_at_z_being_40mm.png
|
 |
| Attachment 2: beam_fit_at_z_being_40mm.png
|
 |
| Attachment 3: propagation_fit.png
|
 |
|
143
|
Mon Sep 5 18:06:53 2022 |
Manar Amer | Fixed | report | lasers and optics | Optical room | Telescope / amplifier output |
Am adjustment on the lenses position to have a smaller waist.
+ 250 mm @ 88 cm from amplifier
-150 mm @ 111 cm from amplifier
the overlap with this placement is ~ 91%
the measured beam FWHM at the injection point M1 estimated to be ~ 0.94 mm
waist = 0.85*0.94 = 0.79 mm , it is still much larger than the needed 0.58 mm radius waist.
There is an improvement in reducing higher order modes, but the fundamental is still too weak to see, we observe higher order even modes 11 , 44 , ...
| Manar Amer wrote: |
|
Note the correct beam divergence is approximately ~ 2.3 mrad
M2 = 1.1 in this fit, but it is not yet optimized !!!!! could be reason for not accurate telescope reading.
Have tInstalled a new telescope with lenses
250 mm @ 86.8 cm from amplifier ,
-150 mm @109 cm (~ 22 cm between lenses)
the beam waist measured at a point on the reflection which is relatively the same distance to the injection mirror and the beam was much smaller than before
@ ~ 2 meters from amplifier + telescope , FWHM = 1.2 mm , waist = 0.85 * FWHM = 1.02 mm
| Manar Amer wrote: |
|
Here is a view of beam propagation in the optical software : GaussianBeam
the red filled shape is the model of the CELIA amplifier beam propagation with a divergence of 4.46 mrad
(the 2 black dots is the measurement of the beam size without any lens to change the beam propagation).
the 2 black lines have been put at the input and output cavity mirrors position relative to the CELIA amplifier position, respectively 2m and 2.7m roughly.
the cavity mode radius should be 0.55mm and 0.7mm respectively.
the cavity mode shape is represented by the 2 red lines (very close to the red filled shape which is the beam).
the most simple working telescope could be a +250 lens at 280mm from the CELIA amplifier.
it gives a beam radius of 0.53mm at the input mirror and 0.64mm at the output mirror.
the overlapping is more than 99%
the 2nd file is the GaussianBeam file.
| Manar Amer wrote: |
|
I placed a periscope to adjust the high of the beam from the amplifier output from ~ 10 cm from the table to ~ 15 cm
a dichroic mirror placed after it to reject the pump laser, all the mirrors on the path to the cavity were replaced with dielectric mirrors BB01-E03
the length of the path from the amplifier output to the cavity coupling mirror ~ 2 meters
setup defines the different optics placed in the path
Note: the beam goes all the way to the cavity, put it is not yet optimized to the irises.
| Manar Amer wrote: |
|
Beam divergence was measured using a method called "Focal Length Divergence Measurement Method"
Where a lens of a known focal length is placed on the beam path and the beam waist is measured at the focal distance using a beam profiler.
We ramped the power up to 10 W
for a focal length = 400 mm,
we measured a FWHM = 2.1 mm,
corresponding to a divergence = 4.45 mrad (edit : wrong software use)
for comparison, we measured the FWHM 8.1 mm @ 1.55 m and extracted the divergence directly 4.46 mrad (edit : this measurement is wrong - wrong use of the software)
Note: better to use a lens of a focal lens higher than 100 mm (to reduce the error in the distance measured)
| Manar Amer wrote: |
|
The previous Sbox telescope was dismantled and the mechanical components cleaned.
its lenses are still in the mounts, it looks that two of them are spherical and two are cylindrical
2 are -100 mm and 2 are +150 mm, there is also a box containing fused silica lenses that could be used.
Note: at high power use only fused silica lenses not BK7 type
|
|
|
|
|
|
| Attachment 1: 20220905_Telescope_lense_placement.jpg
|
 |
|
142
|
Fri Sep 2 18:10:10 2022 |
Manar Amer | Fixed | report | lasers and optics | Optical room | Telescope / amplifier output |
Note the correct beam divergence is approximately ~ 2.3 mrad
M2 = 1.1 in this fit, but it is not yet optimized !!!!! could be reason for not accurate telescope reading.
Have tInstalled a new telescope with lenses
250 mm @ 86.8 cm from amplifier ,
-150 mm @109 cm (~ 22 cm between lenses)
the beam waist measured at a point on the reflection which is relatively the same distance to the injection mirror and the beam was much smaller than before
@ ~ 2 meters from amplifier + telescope , FWHM = 1.2 mm , waist = 0.85 * FWHM = 1.02 mm
| Manar Amer wrote: |
|
Here is a view of beam propagation in the optical software : GaussianBeam
the red filled shape is the model of the CELIA amplifier beam propagation with a divergence of 4.46 mrad
(the 2 black dots is the measurement of the beam size without any lens to change the beam propagation).
the 2 black lines have been put at the input and output cavity mirrors position relative to the CELIA amplifier position, respectively 2m and 2.7m roughly.
the cavity mode radius should be 0.55mm and 0.7mm respectively.
the cavity mode shape is represented by the 2 red lines (very close to the red filled shape which is the beam).
the most simple working telescope could be a +250 lens at 280mm from the CELIA amplifier.
it gives a beam radius of 0.53mm at the input mirror and 0.64mm at the output mirror.
the overlapping is more than 99%
the 2nd file is the GaussianBeam file.
| Manar Amer wrote: |
|
I placed a periscope to adjust the high of the beam from the amplifier output from ~ 10 cm from the table to ~ 15 cm
a dichroic mirror placed after it to reject the pump laser, all the mirrors on the path to the cavity were replaced with dielectric mirrors BB01-E03
the length of the path from the amplifier output to the cavity coupling mirror ~ 2 meters
setup defines the different optics placed in the path
Note: the beam goes all the way to the cavity, put it is not yet optimized to the irises.
| Manar Amer wrote: |
|
Beam divergence was measured using a method called "Focal Length Divergence Measurement Method"
Where a lens of a known focal length is placed on the beam path and the beam waist is measured at the focal distance using a beam profiler.
We ramped the power up to 10 W
for a focal length = 400 mm,
we measured a FWHM = 2.1 mm,
corresponding to a divergence = 4.45 mrad (edit : wrong software use)
for comparison, we measured the FWHM 8.1 mm @ 1.55 m and extracted the divergence directly 4.46 mrad (edit : this measurement is wrong - wrong use of the software)
Note: better to use a lens of a focal lens higher than 100 mm (to reduce the error in the distance measured)
| Manar Amer wrote: |
|
The previous Sbox telescope was dismantled and the mechanical components cleaned.
its lenses are still in the mounts, it looks that two of them are spherical and two are cylindrical
2 are -100 mm and 2 are +150 mm, there is also a box containing fused silica lenses that could be used.
Note: at high power use only fused silica lenses not BK7 type
|
|
|
|
|
| Attachment 1: Ampli_Celia_2.3mrad_divergence_New_Telescope.jpg
|
 |
| Attachment 2: Beam_waist_at_injection_image.jpg
|
 |
|
141
|
Fri Sep 2 17:50:21 2022 |
Manar Amer | Fixed | report | lasers and optics | Optical room | Telescope / amplifier output |
removing the reading which is not correct (wrong use of software)
redone a reading similar using a lens of focal 250 mm got a FWHM-X = 0.64 mm , FWHM-Y = 0.84 mm
using the vertical to calculate the divergence, we get divergence ~ 2.17 mrad which is closer to fit obtained for the beam profile by taking data points along the path
attached is also the amplifier beam data taken at different points and their fit using Gaussian beam software
for a focal length = 400 mm,
we measured a FWHM = 2.1 mm,
corresponding to a divergence = 4.45 mrad
| Manar Amer wrote: |
|
Beam divergence was measured using a method called "Focal Length Divergence Measurement Method"
Where a lens of a known focal length is placed on the beam path and the beam waist is measured at the focal distance using a beam profiler.
We ramped the power up to 10 W
for a focal length = 400 mm,
we measured a FWHM = 2.1 mm,
corresponding to a divergence = 4.45 mrad (edit : wrong software use)
for comparison, we measured the FWHM 8.1 mm @ 1.55 m and extracted the divergence directly 4.46 mrad (edit : this measurement is wrong - wrong use of the software)
Note: better to use a lens of a focal lens higher than 100 mm (to reduce the error in the distance measured)
| Manar Amer wrote: |
|
The previous Sbox telescope was dismantled and the mechanical components cleaned.
its lenses are still in the mounts, it looks that two of them are spherical and two are cylindrical
2 are -100 mm and 2 are +150 mm, there is also a box containing fused silica lenses that could be used.
Note: at high power use only fused silica lenses not BK7 type
|
|
|
| Attachment 1: Beam_Profile_Fit_using_gaussian_Beam.jpg
|
 |
| Attachment 2: Beam_Profile_Fit_using_gaussian_Beam.xml
|
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE gaussianBeam>
<gaussianBeam version="1.1">
<bench id="0">
<wavelength>1.03e-06</wavelength>
<leftBoundary>-0.1</leftBoundary>
<rightBoundary>4</rightBoundary>
<targetBeam id="0">
<position>2</position>
<waist>0.00058</waist>
<positionTolerance>0.1</positionTolerance>
<waistTolerance>0.05</waistTolerance>
<minOverlap>0.96</minOverlap>
<overlapCriterion>1</overlapCriterion>
</targetBeam>
<beamFit id="0">
<name>Fit0</name>
<dataType>3</dataType>
<color>4278190080</color>
<data id="0">
<position>0.1</position>
<value>0.000132</value>
</data>
<data id="1">
<position>0.15</position>
<value>0.00017</value>
</data>
<data id="2">
<position>0.25</position>
<value>0.000484</value>
</data>
<data id="3">
<position>0.27</position>
<value>0.000561</value>
</data>
<data id="4">
<position>0.3</position>
<value>0.00066</value>
</data>
<data id="5">
<position>0.32</position>
<value>0.000698</value>
</data>
<data id="6">
<position>0.35</position>
<value>0.000753</value>
</data>
<data id="7">
<position>0.38</position>
<value>0.000858</value>
</data>
<data id="8">
<position>0.4</position>
<value>0.000891</value>
</data>
<data id="9">
<position>0.43</position>
<value>0.000979</value>
</data>
<data id="10">
<position>0.5</position>
<value>0.001138</value>
</data>
<data id="11">
<position>0.52</position>
<value>0.001215</value>
</data>
<data id="12">
<position>0.55</position>
<value>0.001188</value>
</data>
<data id="13">
<position>0.6</position>
<value>0.001265</value>
</data>
<data id="14">
<position>0.65</position>
<value>0.001512</value>
</data>
<data id="15">
<position>0.7</position>
<value>0.001617</value>
</data>
<data id="16">
<position>0.75</position>
<value>0.001749</value>
</data>
<data id="17">
<position>0.8</position>
<value>0.001837</value>
</data>
<data id="18">
<position>0.85</position>
<value>0.001782</value>
</data>
<data id="19">
<position>0.9</position>
<value>0.002183</value>
</data>
<data id="20">
<position>1</position>
<value>0.002469</value>
</data>
<data id="21">
<position>1.1</position>
<value>0.002706</value>
</data>
</beamFit>
<beamFit id="1">
<name>Fit4</name>
<dataType>1</dataType>
<color>0</color>
<data id="0">
<position>0</position>
<value>0</value>
</data>
<data id="1">
<position>0</position>
<value>0</value>
</data>
<data id="2">
<position>0</position>
<value>0</value>
</data>
</beamFit>
<opticsList>
<inputBeam id="2">
<waist>0.000151751</waist>
<index>1</index>
<M2>1.1</M2>
<position>0.0620946</position>
<name>w0</name>
<absoluteLock>1</absoluteLock>
</inputBeam>
</opticsList>
</bench>
<view id="0" bench="0">
<horizontalRange>2.99</horizontalRange>
<verticalRange>0.00715</verticalRange>
<origin>-0.100473</origin>
<showTargetBeam id="0">0</showTargetBeam>
</view>
</gaussianBeam>
|
|
140
|
Wed Aug 31 18:14:51 2022 |
Ronic Chiche | Fixed | info | lasers and optics | Optical room | 2nd stage CELIA amplifier |
today we did several test with the Dichroic shortpass mirror (Thorlabs DMSP1000) and with a 10nm optical filter around 1030nm (which works in tranmission at AOI=0).
one used the dichroic mirror in reflection: one should cut the pump @970-990nm and we should keep only the signal @1030nm.
but we still saw plenty spots around the central beam (see the image).
adding the 10nm optical filter on the camera, the image did not change !
then we confirmed the whole signal (centered beam + spots) are well @1030nm.
this spots could be the remaining high order modes of the large fiber used for the 3rd stage of the amplifier.
| Ronic Chiche wrote: |
|
today, we measured the 2nd stage CELIA amplifier pump wavelength : 970-990 nm
|
|
| Attachment 1: image_faisceau_multimode_@1030nm.PNG
|
 |
|
139
|
Tue Aug 30 17:48:39 2022 |
Ronic Chiche | Fixed | info | lasers and optics | Optical room | 2nd stage CELIA amplifier |
today, we measured the 2nd stage CELIA amplifier pump wavelength : 970-990 nm |
| Attachment 1: 2nd_stage_pump_wavelength.jpg
|
 |
|
138
|
Wed Aug 24 10:45:24 2022 |
Manar Amer | Fixed | report | lasers and optics | Optical room | 2 Mirror Setup @ 216.6 MHz |
Adding information about the 2 mirror cavity setup (plan - spherical) that is currently installed.
From Aurélien at the start of the manipulation.
@ 0 is where the injection mirror is located
| 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: manip2miroirs.pptx
|
| Attachment 2: 2mirror_plan_shperical_beam_size.png
|
 |
|
137
|
Wed Aug 24 10:39:58 2022 |
Manar Amer | Fixed | report | lasers and optics | Optical room | Telescope / amplifier output |
Here is a view of beam propagation in the optical software : GaussianBeam
the red filled shape is the model of the CELIA amplifier beam propagation with a divergence of 4.46 mrad
(the 2 black dots is the measurement of the beam size without any lens to change the beam propagation).
the 2 black lines have been put at the input and output cavity mirrors position relative to the CELIA amplifier position, respectively 2m and 2.7m roughly.
the cavity mode radius should be 0.55mm and 0.7mm respectively.
the cavity mode shape is represented by the 2 red lines (very close to the red filled shape which is the beam).
the most simple working telescope could be a +250 lens at 280mm from the CELIA amplifier.
it gives a beam radius of 0.53mm at the input mirror and 0.64mm at the output mirror.
the overlapping is more than 99%
the 2nd file is the GaussianBeam file.
| Manar Amer wrote: |
|
I placed a periscope to adjust the high of the beam from the amplifier output from ~ 10 cm from the table to ~ 15 cm
a dichroic mirror placed after it to reject the pump laser, all the mirrors on the path to the cavity were replaced with dielectric mirrors BB01-E03
the length of the path from the amplifier output to the cavity coupling mirror ~ 2 meters
setup defines the different optics placed in the path
Note: the beam goes all the way to the cavity, put it is not yet optimized to the irises.
| Manar Amer wrote: |
|
Beam divergence was measured using a method called "Focal Length Divergence Measurement Method"
Where a lens of a known focal length is placed on the beam path and the beam waist is measured at the focal distance using a beam profiler.
We ramped the power up to 10 W
for a focal length = 400 mm,
we measured a FWHM = 2.1 mm,
corresponding to a divergence = 4.45 mrad (edit : wrong software use)
for comparison, we measured the FWHM 8.1 mm @ 1.55 m and extracted the divergence directly 4.46 mrad (edit : this measurement is wrong - wrong use of the software)
Note: better to use a lens of a focal lens higher than 100 mm (to reduce the error in the distance measured)
| Manar Amer wrote: |
|
The previous Sbox telescope was dismantled and the mechanical components cleaned.
its lenses are still in the mounts, it looks that two of them are spherical and two are cylindrical
2 are -100 mm and 2 are +150 mm, there is also a box containing fused silica lenses that could be used.
Note: at high power use only fused silica lenses not BK7 type
|
|
|
|
| Attachment 1: Capture.PNG
|
 |
| Attachment 2: Telescope_AMPLI_CELIA_1.xml
|
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE gaussianBeam>
<gaussianBeam version="1.1">
<bench id="0">
<wavelength>1.03e-06</wavelength>
<leftBoundary>-0.1</leftBoundary>
<rightBoundary>5</rightBoundary>
<targetBeam id="0">
<position>2</position>
<waist>0.00055</waist>
<positionTolerance>0.1</positionTolerance>
<waistTolerance>0.05</waistTolerance>
<minOverlap>0.98</minOverlap>
<overlapCriterion>1</overlapCriterion>
</targetBeam>
<beamFit id="0">
<name>Fit6</name>
<dataType>1</dataType>
<color>0</color>
<data id="0">
<position>0.5</position>
<value>0.00444</value>
</data>
<data id="1">
<position>0</position>
<value>0</value>
</data>
<data id="2">
<position>0</position>
<value>0</value>
</data>
</beamFit>
<opticsList>
<inputBeam id="2">
<waist>7.35105e-05</waist>
<index>1</index>
<M2>1</M2>
<position>0</position>
<name>w0</name>
<absoluteLock>1</absoluteLock>
</inputBeam>
<lens id="24">
<focal>0.25</focal>
<position>0.280458</position>
<name>L7</name>
<absoluteLock>0</absoluteLock>
</lens>
<dielectricSlab id="26">
<indexRatio>1</indexRatio>
<width>0.001</width>
<position>2.02206</position>
<name>D3</name>
<absoluteLock>0</absoluteLock>
</dielectricSlab>
<dielectricSlab id="23">
<indexRatio>1</indexRatio>
<width>0.001</width>
<position>2.7</position>
<name>D2</name>
<absoluteLock>0</absoluteLock>
</dielectricSlab>
</opticsList>
</bench>
<view id="0" bench="0">
<horizontalRange>3</horizontalRange>
<verticalRange>0.01</verticalRange>
<origin>0</origin>
<showTargetBeam id="0">1</showTargetBeam>
</view>
</gaussianBeam>
|
|
136
|
Tue Aug 23 17:37:38 2022 |
Manar Amer | Fixed | report | lasers and optics | Optical room | Telescope / amplifier output |
I placed a periscope to adjust the high of the beam from the amplifier output from ~ 10 cm from the table to ~ 15 cm
a dichroic mirror placed after it to reject the pump laser, all the mirrors on the path to the cavity were replaced with dielectric mirrors BB01-E03
the length of the path from the amplifier output to the cavity coupling mirror ~ 2 meters
setup defines the different optics placed in the path
Note: the beam goes all the way to the cavity, put it is not yet optimized to the irises.
| Manar Amer wrote: |
|
Beam divergence was measured using a method called "Focal Length Divergence Measurement Method"
Where a lens of a known focal length is placed on the beam path and the beam waist is measured at the focal distance using a beam profiler.
We ramped the power up to 10 W
for a focal length = 400 mm,
we measured a FWHM = 2.1 mm,
corresponding to a divergence = 4.45 mrad (edit : wrong software use)
for comparison, we measured the FWHM 8.1 mm @ 1.55 m and extracted the divergence directly 4.46 mrad (edit : this measurement is wrong - wrong use of the software)
Note: better to use a lens of a focal lens higher than 100 mm (to reduce the error in the distance measured)
| Manar Amer wrote: |
|
The previous Sbox telescope was dismantled and the mechanical components cleaned.
its lenses are still in the mounts, it looks that two of them are spherical and two are cylindrical
2 are -100 mm and 2 are +150 mm, there is also a box containing fused silica lenses that could be used.
Note: at high power use only fused silica lenses not BK7 type
|
|
|
| Attachment 1: 20220823_setup.jpg
|
 |
|
135
|
Mon Aug 22 18:39:13 2022 |
Manar Amer | Fixed | report | lasers and optics | Optical room | Amplifier output Beam Profile |
Beam divergence after amplifier 4.46 mrad
| Manar Amer wrote: |
|
In preparation to measure the output beam profile from the amplifier at high power, I have placed two wedge mirrors just before the beam dump to be able to extract the beam.
One of the wedges was taken from ThomX bunker, also the HR and AR mirrors were taken to plic room in case we might need them
an updated setup is attached
|
|
|
134
|
Mon Aug 22 18:38:03 2022 |
Manar Amer | Fixed | report | lasers and optics | Optical room | Telescope / amplifier output |
Beam divergence was measured using a method called "Focal Length Divergence Measurement Method"
Where a lens of a known focal length is placed on the beam path and the beam waist is measured at the focal distance using a beam profiler.
We ramped the power up to 10 W
for a focal length = 400 mm,
we measured a FWHM = 2.1 mm,
corresponding to a divergence = 4.45 mrad (edit : wrong software use)
for comparison, we measured the FWHM 8.1 mm @ 1.55 m and extracted the divergence directly 4.46 mrad (edit : this measurement is wrong - wrong use of the software)
Note: better to use a lens of a focal lens higher than 100 mm (to reduce the error in the distance measured)
| Manar Amer wrote: |
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The previous Sbox telescope was dismantled and the mechanical components cleaned.
its lenses are still in the mounts, it looks that two of them are spherical and two are cylindrical
2 are -100 mm and 2 are +150 mm, there is also a box containing fused silica lenses that could be used.
Note: at high power use only fused silica lenses not BK7 type
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| Attachment 1: Focal_length_divergence_method.pdf
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| Attachment 2: Beam_Profile_at_high_power_.jpg
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| Attachment 3: SBOX_CELIA_AMPLIFIER_Divergence_measurement.pdf
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Fri Aug 19 16:36:18 2022 |
Manar Amer | Fixed | report | lasers and optics | Optical room | Telescope / amplifier output |
The previous Sbox telescope was dismantled and the mechanical components cleaned.
its lenses are still in the mounts, it looks that two of them are spherical and two are cylindrical
2 are -100 mm and 2 are +150 mm, there is also a box containing fused silica lenses that could be used.
Note: at high power use only fused silica lenses not BK7 type
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Fri Aug 19 16:31:11 2022 |
Manar Amer | Fixed | report | lasers and optics | Optical room | Amplifier output Beam Profile |
In preparation to measure the output beam profile from the amplifier at high power, I have placed two wedge mirrors just before the beam dump to be able to extract the beam.
One of the wedges was taken from ThomX bunker, also the HR and AR mirrors were taken to plic room in case we might need them
an updated setup is attached |
| Attachment 1: 20220819_Setup.jpg
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Fri Aug 19 16:03:40 2022 |
Manar Amer | Fixed | report | lasers and optics | detectors and electronics | software | Optical room | CVBG stretching / Fiber Injection |
closing series
| Manar Amer wrote: |
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Before injecting into the amplifier, the pulse needs to be stretched using a CVBG, type attached.
the CVBG is to be used at a small angle, the beam shape and spectrum after the PBS is attached.
After measuring the beam profile, a mirror was placed to direct all the power for fiber injection
power before the fiber is 13 mW and the power injected is 6.19 mW
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Fri Aug 19 16:03:17 2022 |
Manar Amer | Fixed | report | lasers and optics | detectors and electronics | software | Optical room | Alignment / Table setup |
closing series
| Manar Amer wrote: |
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The current setup of the optical table attached.
The cavity is aligned and the lock of the fundamental mode has been attempted, but the mode is drifting too quickly to be able to follow.
I have placed the cavity under vacuum for a better stability.
a simple telescope for the CW was adjusted to having 2 lenses of 300 mm placed ~ 250 mm away from the colimator and 200 mm lens placed after it with 510 mm.
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Fri Aug 19 16:02:33 2022 |
Manar Amer | Fixed | report | lasers and optics | detectors and electronics | software | Optical room | CELIA amplifier installation + chiller |
Closing series
| Manar Amer wrote: |
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The software to control the CELIA amplifier is on the laptop that was placed in ThomX bunker.
I have placed it in the PLIC room next to the SBox table.
it is called 'Alphanov Control Software'
| Manar Amer wrote: |
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Amplifier placed next to the pulsed laser on the table under the airflow
The output is in free space with height from the table of about 10 cm, note the injection height into the cavity is between 14 - 15 cm.
a power cable is placed but not plugged.
Connection to the computer is made using USB B on amplifier to USB A (note need a longer cable, the available on is too short)
The cooling, to be connected to an outside chiller, will use the bottom one shown in the image attached.
The two water tubes, from chiller to amplifier, has been marked. The size of the tubes from the amplifier fit inside the tubes from the chiller.
| Manar Amer wrote: |
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The amplifier was installed on the optical table next to SBox table.
The CVBG that will be used for stretching before amplification needs cleaning (they are very fragile, 'ask victor for best method')
The software to drive the diodes of the amplifier we have is not the compatible one.
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Fri Aug 12 17:48:28 2022 |
Ronic Chiche | Fixed | report | lasers and optics | Optical room | "ThomX" CELIA Amplifier commissionning |
this afternoon, with Fabian, we did some measurements on the 3rd stage.
finally we used the Dichroïc mirror at AOI=45°C as first mirror and a Thorlabs BB1-E03 as 2nd mirror to send the beam to the powermeter.
we put an iris to cut the pump beam part.
with only the 2nd stage ON, the dirchroïc mirror and the iris : P=0.4W
3RD STAGE
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IT IS MANDATORY TO SWITCH ON THE CHILLER
once the Alphanov software is launched, 4 windows appears on the screeen, one for each diode.
once the chiller temperature reach the set value (23°C in our case), one can start to increase the pump current.
(set "voltage adj." to AUTO)
the TEC of the first diode is not operative, then we decided to stop its current to 4A to avoid a too large temperature (in this condition, the temperature of the diode reach ~45°C !)
the other diodes temperatures are stabilized around 25°C
1A for all diodes => 1 W
2A for all diodes => 10.7 W
3A for all diodes => 22 W
4A for all diodes => 33 W
5A for diodes 2-3-4 => 40.5 W
6A for diodes 2-3-4 => 48.1 W
we stopped the measurement at 6A and we did not notice any change in the optical spectrum
During the optical spectrum measurement we tried to use a NDUV20 Thorlabs reflective filter to reflect the high power beam to the powermeter and let a few power part be transmitted to the spectral measurement.
unfortunatelly, the ND filter coating has been completly removed => DO NOT USE Thorlabs ND filters at high power !
| Ronic Chiche wrote: |
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Beam size at the amplifier output:
to make this measurement, I switched ON only 1st and 2nd stage.
the dichroïc mirror seems to work the best in reflection at normal AOI !!!
it's strange as most dichroïc mirrors seem to be specified at AOI = 45° ! => to be checked ! => the dichroïc mirror was set on its wrong face !!! => problem solved
the 2 images correspond to the beam measured at 24cm from the amplifier output.
we cannot use the gaussian fit due to the pump beam shape which perturbate the measurement.
I used the FWHM measurement => DX = 2.6 mm, DY = 1.8mm
Pulse shape model:
dP(x,y,t) = DP * exp( - ln(2) * ( (x/DX_fwhm)² + (y/DY_fwhm)² ) * sech²( t / tp )
=> can we use safely the Newport 20Z40DM.10 mirrors to transport the amplifier beam ?
they are specified for 500 W/cm2 CW and 4 J/cm2 for 10 nsec pulses @ 1064 nm.
- if I am correct, for the previous shape model, the average power is :
Pmoy (W) = 2pi / ln(2) * tp * DP * DX_fwhm * DY_fwhm * Frep
with DP=500W/cm2, DX_fwhm=2.6mm DY_fwhm=1.8mm, tp=77ps, Frep=216MHz => Pmoy = 3.5 W !!!
this means that we should not exceed this average power with these mirrors !?!
- if I am correct, for the previous shape model, the maximal energy density (in the pulse center) is :
DE (J/cm2) = tp * DP => Pmoy = 2pi / ln(2) * DE * DX_fwhm * DY_fwhm * Frep
with DE= 4J/cm2, DX_fwhm=2.6mm DY_fwhm=1.8mm, Frep=216MHz => Pmoy = 366 MW !!!
if one applies a safety factor due to the pulse duration ratio (77ps / 10ns) => Pmoy = 2.8 MW !
this specification seems much less restrictive !
=> can we use safely the Thorlabs BB1-E03 mirrors to transport the amplifier beam ?
they are specified for 10 kW/cm CW (linear power density) and 0.5 J/cm2 for 10 nsec pulses @ 1064 nm.
- the linear power density (LPD) is defined as the average power divided by the beam diameter (1/e²)
LPD = Pmoy / DXY = Pmoy / (1.7 DXY_fwhm) => Pmoy = LPD * 1.7 DXY_fwhm
with LPD=10kW/cm and DY_fwhm=1.8mm => Pmoy = 3 kW
- for maximal energy density:
with DE= 0.5J/cm2, DX_fwhm=2.6mm DY_fwhm=1.8mm, Frep=216MHz => Pmoy = 45 MW !!!
if one applies a safety factor due to the pulse duration ratio (77ps / 10ns) => Pmoy = 350 kW !
| Ronic Chiche wrote: |
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The "ThomX" CELIA amplifier is installed on the optical table.
I added all the rubber pieces available between the 2 racks to isolate as best as possible the top rack, which embeds some fans, from the bottom rack from which the laser beam is going out to the FP cavity.
1ST STAGE
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if I put 1mW (minimum input power) on the input fiber of the amplifier and I switch ON the first stage, one can measure 7mW on the 5% output tap on the front panel.
then it is mandatory to check this power before swtiching ON the other stage.
this 5% output tap on the front panel MUST BE ABOVE 7mW
input power : 1mW => 5% output tap : 7mW => amplifier output : 260µW
with the present setup, I can reach 6.8mW of input power, but the 5% output tap seems to saturate at ~ 8mW.
in this condition, the amplifier output is around 800µW
the SMA connector on the rear panel does not output any signal with the 1st stage ON.
2ND STAGE
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then, one can switch ON the 2nd stage : amplifier output is around 1.4 W (without any iris or dichroïc mirror).
the SMA connector on the rear panel does not output any signal with the 2nd stage ON.
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Fri Aug 12 11:46:17 2022 |
Ronic Chiche | Fixed | info | lasers and optics | Optical room | OEwaves lock and Finesse measurement |
this morning, I locked the FP cavity with the OEwaves CW laser and the "Fred fiber amplifier" used at 500mA of pump current.
the lock was much more easy than with the Koheras.
I had to change the 10GHz EOM which seems damaged as the modulation depth is very low and does not allow a Finesse measurement by modulation technique.
I changed it by a recently buyed 2GHz EOM... the modulation depth is large enough and we can make the Finesse measurement.
I took several sets of data and the average Finesse is 25.5k ! |
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Thu Aug 11 19:27:09 2022 |
Ronic Chiche | Fixed | info | lasers and optics | detectors and electronics | Optical room | Koheras CW laser lock on FP cavity |
I locked the Koheras CW on the FP cavity but the lock was pretty noisy and very difficult to acquire.
I tried to produce some modulation sidebands close to 216MHz to measure the Finesse but the power loss was very small so, the signal to extract the Finesse would be unreadable !
(generator voltage was at maximum Vout = 0.5Vrms on 50 ohms... is it normal ? or the used 10GHz EOM suffers some problems ?)
At one moment, I lost the lock and was not able to find it again... it seems the Koheras is too noisy for this cavity (may be is it a good news for the Finesse ?).
Tomorrow, I will try to use the OEwave + amplifier to lock the cavity.
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