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 |
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. |
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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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D-shape mirrors positionning status, posted by Ronic Chiche at Optical room about mechanics | lasers and optics | detectors and electronics
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This afternoon we opened the cavity and put the D-shape mirrors at their correct place, close to the beam.
we checked the relative position of the mirrors to the beam using the 2nd stage of the amplifier (<1W) and with the sensitive (and cleaned) orange
optical card. |
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D-shape mirrors positionning status, posted by Ronic Chiche at Optical room about mechanics | lasers and optics | detectors and electronics
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The cavity box is vacuum pumped at 6*10^-2 mbar.
Ronic
Chiche wrote:
This afternoon we opened the cavity and put the D-shape mirrors at |
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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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Damage on mirror surface , posted by Manar Amer at Optical room about lasers and optics
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Following the storage of ~ 50 kW inside the cavity and a sudden drop in transmitted power from the cavity
damage to the mirror surface was suspected.
We broke vacuum and took images of the surface of the 2 mirrors in the cavity, the spherical and the planar mirror |