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 |
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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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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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. |
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. |
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Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
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We locked the cavity, and it is stable using the Transmission,
the high frequency that we thought could have a reason for instability, is due to the high power on the photo diode of the PDH box which can
cause non-linearity effects in the signal. |
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Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
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image of the lock with Coupling of ~ 60%
Manar |
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Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
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Alignment was improved to ~ 1.2 V on the photodiode.
Only the second stage was on with ~ 1 W output from amplifier
we measured the transmission from S2 to be 2.3 mW |
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Power storage In Cavity, posted by Manar Amer at Optical room about lasers and optics
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We start of power output from amplifier of 1W with only the first and second stage on then we start with the third stage power increase,
Note: when changing the current on the third stage 4 diodes, better to do it step by step for each one with a step of ~ 0.5 A
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Power storage In Cavity, posted by Manar Amer at Optical room about lasers and optics
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At transmission power of 42 mW, coupling 60%, we see fundamental mode with a degeneracy
The D-shape motors were moved to a position 2 000 000 steps (in theory they should be the max position)
but no change appeared on the 00 mode or the higher order mode. |
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Power storage In Cavity, posted by Manar Amer at Optical room about lasers and optics
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Power increased in the amplifier
reflective filters added at the transmission point to be able to have signal on the Beam Profiler, Transmission diode and power meter
Amplifier output current |
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Power storage In Cavity, posted by Manar Amer at Optical room about lasers and optics
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at max stage we reached at 2.5 A on the diodes we have
8000 gain , coupling ~ 60% , with power inside the cavity 50 kW
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