"ThomX" CELIA Amplifier commissionning, posted by Ronic Chiche at Optical room about lasers and optics
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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. |
Amplifier output Beam Profile, posted by Manar Amer at Optical room about lasers and optics 
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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 |
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Telescope / amplifier output, posted by Manar Amer at Optical room about lasers and optics
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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. |
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Telescope / amplifier output, posted by Manar Amer at Optical room about lasers and optics
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Beam divergence was measured using a method called "Focal
Length Divergence
Measurement Method" |
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Amplifier output Beam Profile, posted by Manar Amer at Optical room about lasers and optics
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Beam divergence after amplifier 4.46 mrad
Manar |
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Telescope / amplifier output, posted by Manar Amer at Optical room about lasers and optics
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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 |
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Telescope / amplifier output, posted by Manar Amer at Optical room about lasers and optics
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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). |
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2 Mirror Setup @ 216.6 MHz, posted by Manar Amer at Optical room about lasers and optics
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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 |
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2nd stage CELIA amplifier, posted by Ronic Chiche at Optical room about lasers and optics
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| today, we measured the 2nd stage CELIA amplifier pump wavelength : 970-990 nm |
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2nd stage CELIA amplifier, posted by Ronic Chiche at Optical room about lasers and optics
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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. |
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Telescope / amplifier output, posted by Manar Amer at Optical room about lasers and optics
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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 |
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Telescope / amplifier output, posted by Manar Amer at Optical room about lasers and optics
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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. |
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Telescope / amplifier output, posted by Manar Amer at Optical room about lasers and optics
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Am adjustment on the lenses position to have a smaller waist.
+ 250 mm @ 88 cm from amplifier
-150 mm @ 111 cm from amplifier |
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unsuccessful telescope design :-(, posted by Ronic Chiche at Optical room about lasers and optics
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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). |
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Telescope / amplifier output, posted by Manar Amer at Optical room about lasers and optics
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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. |
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Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
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Today we managed to observe the fundamental mode and stabilize the scan on it until we improved the alignment enough.
We see some coupling, but it is very week < 5% , We improved the alignment and the polarization, but there is still no explanation to why
it is very low. |
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Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
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Today, we played on the CEP but using the I-tune input of the Menhir Laser (+/- 5V maximal range).
unfortunately, one only saw a very weak improvement of the transmission by 10-20%... and the coupling improvement is almost zero.
the best improvement was for the maximal I-tune range (+5V) which maybe means that we could improve more the effect if were able to get a full |
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Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
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We played on the CEP using the USB command "id0=xxxxx" of the Menhir.
we put id0=48650 and we improved A LOT the transmission and coupling (~ 60%)
here is an image of the first attempts to lock... but the locking is quite difficult. |
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Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
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We managed to lock the cavity by adding the AOM , but the lock is still difficult to stabilize.
There is some high frequency compensated by the AOM at ~ 170 kHz (yet to understand from where it comes from)
Manar |
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Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
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We wanted to increase the power of the amplifier to measure the transmission output at M2,
but locking the cavity again was very, very difficult.
We will try again tomorrow. |