Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics 
|
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. |
Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
|
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 |
|
Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
|
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. |
|
Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
|
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 |
|
Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
|
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. |
|
Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
|
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. |
|
Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
|
image of the lock with Coupling of ~ 60%
Manar |
|
Locking Amplifier with Cavity , posted by Manar Amer at Optical room about lasers and optics
|
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 |
|
Power storage In Cavity, posted by Manar Amer at Optical room about lasers and optics
|
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
|
|
Power storage In Cavity, posted by Manar Amer at Optical room about lasers and optics
|
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. |
|
D-shape mirrors positionning status, posted by Ronic Chiche at Optical room about mechanics | lasers and optics | detectors and electronics
|
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. |
|
D-shape mirrors positionning status, posted by Ronic Chiche at Optical room about mechanics | lasers and optics | detectors and electronics
|
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 |
|
Power storage In Cavity, posted by Manar Amer at Optical room about lasers and optics
|
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 |
|
Power storage In Cavity, posted by Manar Amer at Optical room about lasers and optics
|
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
|
|
Damage on mirror surface , posted by Manar Amer at Optical room about lasers and optics
|
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 |
|
Damage on mirror surface , posted by Manar Amer at Optical room about lasers and optics
|
Tomorrow will try to shift the injection mirror to avoid hitting the damaged spot.
Manar |
|
Damage on mirror surface , posted by Manar Amer at Optical room about lasers and optics
|
After discussing, we have decided against shifting the mirror to avoid the time lost.
We changed the injection mirror to a different mirror from Mighty Laser set, Transmission of mirror 80
ppm. (no visible damage at the center of the mirror, only a small scratch on the back) |
|
liPower storage In Cavity, posted by Manar Amer at Optical room about lasers and optics
|
After changing the mirror M1 and cleaning the 2 mirrors
They were placed in the cavity box (avoiding touching the mounts to not affect the alignment and placing the mirrors as close to the previous
position) |
|
Power storage In Cavity, posted by Manar Amer at Optical room about lasers and optics
|
The cavity was locked under vacuum, coupling is approximately < 10%
The lock was relatively easy and the usual sign (oscillations on the transmission tail) of high finesse on the transmission signal was not seen.
|
|
Power storage In Cavity, posted by Manar Amer at Optical room about lasers and optics
|
We improved the lock using the alignment, polarization and CEP , the maximum we got was ~ 12% coupling
only the second stage is on !
Decision : this is the maximum we can obtain using the M1 from mighty laser |