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. |
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 |
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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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 |
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Damage on mirror surface , posted by Manar Amer at Optical room about lasers and optics
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Tomorrow will try to shift the injection mirror to avoid hitting the damaged spot.
Manar |
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Damage on mirror surface , posted by Manar Amer at Optical room about lasers and optics
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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) |
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liPower storage In Cavity, posted by Manar Amer at Optical room about lasers and optics
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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) |
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Power storage In Cavity, posted by Manar Amer at Optical room about lasers and optics
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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.
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Power storage In Cavity, posted by Manar Amer at Optical room about lasers and optics
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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 |
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Damage on mirror surface , posted by Manar Amer at Optical room about lasers and optics
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a better image of the damaged spot, image taken with the arrow for the reflective surface facing the other direction (image shows position)
The image of M1 for ThomX reflective surface was taken at min zoom (full image scale 13 mm) and max zoom (full image scale 2 mm) on microscope
The spot appears to be not close to the center of the mirror, at max zoom in the center we do not see the spot it is just out of the image |
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Damage on mirror surface , posted by Manar Amer at Optical room about lasers and optics
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ThomX injection mirror has been cleaned and placed again inside the optical cavity.
This time to avoid the damaged spot I have displaced the mirror mount horizontally to have a distance between center of the beam and the spot
~ 2.5 - 3 mm. |
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M1 ThomX used while shifted from damaged spot , posted by Manar Amer at Optical room about lasers and optics
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Yesterday , we locked the cavity and we see a sign of a high finesse on the transmission signal, but no measurement of Finesse was done.
we have a coupling of ~ 45%, which is a loss of 20% from the previous coupling of 60%
an estimate done by Ronic MATLAB simulation for the coupling drop where we have 200 pp additional losses and gain of 2.6 k we should get a transmission |
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M1 ThomX used while shifted from damaged spot , posted by Manar Amer at Optical room about lasers and optics
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To compare between the 2 images of the cavity mode:
the mode by itself has an integration time of 0.06 ms, position (x, y) = (1142.969, -53.932) um on the beam profiler
the
mode saturated with the spot next to it almost at max intensity has an integration time of 50 ms, position (-3700, -2000) um
comparing |
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M1 ThomX used while shifted from damaged spot , posted by Manar Amer at Optical room about lasers and optics
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On Wednesday 21st , I opened the cavity did an additional 2 mm shift of the injection mirror and put it under vacuum again.
Locked the cavity, and observed the transmitted beam.
The second spot is still visible on the beam profiler , the distance difference between the 2 spots is ~ 5.2 mm (the same as before ) |
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M1 Gamma Factory, posted by Manar Amer at Optical room about lasers and optics
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In the morning, Vacuum broken and rotated M1 ThomX 90 degrees clockwise, locked the cavity in air and we observe a degeneracy close to the fundamental
mode.
In the afternoon, I cleaned M1 from Gamma factory using pure ethanol and pure water with the spincoater |
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M2 ThomX spherical Cleaning , posted by Manar Amer at Optical room about lasers and optics 6x
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Today, M2 Spherical-3 from ThomX that was installed inside the SBox was removed, there was one big dust on the surface of the mirror, mirror was cleaned
using pure ethanol and pure water with spincoater. (images taken with arrow far from us)
M1 from Gamma factory, fixed with the addition of the ring with 3 screws. |