FSR change & Finesse Measurements , posted by Manar Amer at Optical room about lasers and optics | detectors and electronics
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a Finesse of 30k with the present mirrors :
T1=120 ppm ;A1=(2.6+1) ppm;
T2=1.5 ppm ;A2=(4.5+0.27) ppm; |
FSR and Finesse measurement, posted by Ronic Chiche at Optical room about lasers and optics 
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Yesterday the cavity has been aligned and locked with the CW Koheras laser.
the FSR has been measured by modulation technique at 133.344MHz at 1mbar pressure in the cavity.
the polarization has to be optimized for the Finesse measurement otherwise, some "shoulders" appear beside the Airy peak and reduce |
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FSR and Finesse measurement, posted by Xinyi Lu at Optical room about lasers and optics
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- Today, Ronic and I measured the finesse and FSR after optimizing the locking. FSR was adjusted to 160.27 MHz to match the pulsed laser repetition rate.
The finesse was 3029.
Note: It's now CW laser injected, SBOX's old mirrors. There are lots of dust on the old mirrors without cleaning. |
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Dust Cleaning of SBox, posted by Manar Amer at Optical room about utilities
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An Initial cleaning of the KBoX outside was done, All the optics and mechanics placed that were on the table were removed.
Only the old Mitylaser amplifier remains on the table.
Since we will be using the ThomX Celia amplifier, we will remove it and place it in a secure location (to be decided). |
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Dust Cleaning of SBox, posted by Manar Amer at Optical room about utilities
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The cleaning was done twice with half an hour interval between the two times
reading on the dust meter was taken after each time, and it was zero averaged over a 10-min
Manar |
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Dust Cleaning of SBox, posted by Manar Amer at Optical room about mechanics | lasers and optics | utilities 6x
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The inside of the cavity was cleaned today. It was very dirty and had big dust particles and fibers inside.
Cleaning was done for everything; wall, floor, fixed mounts, wires (still have some dust difficult to remove), edges.
The dust meter average was measured outside the cavity (2471 p/m3 av 6 min) and inside after cleaning (1424 p/m3 av 10 min). |
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Dust Cleaning of SBox, posted by Manar Amer at Optical room about mechanics | lasers and optics | utilities
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After an overnight where the cavity box was left open, a measurement of the Dust meter was taken:
Outside on the optical table on direct air flux (1701 p/m3 Av 10 min) and
Inside the cavity box (998 p/m3 Av 10 min) |
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Divergence of the CW beam after collimator , posted by Manar Amer at Optical room about lasers and optics
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Closing the series of the telescope for the beam @ 133.33 MHz
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Different cavity modes & Pulse width, posted by Xinyi Lu at Optical room about lasers and optics
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- Last week, we obtained three curves of the variation of different cavity modes with power (Fig. 1). By comparing the gain for similar cavity mode sizes,
we found that the gain always drops with increasing power.
- We measured the pulse width. The pulse width of the seed laser, after CVBG, amplified at 2A was measured by UPD (rise time < 70ps). Code |
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Different cavity modes & Pulse width, posted by Xinyi Lu at Optical room about lasers and optics
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Additional information:
The pulse duration has been performed in RF on a UPD-70-IR2-P photodiode from Alphalas GmbH by carefully deconvoluting the response function
of the photodiode measured directly with the sub-picosecond laser beam. |
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Deposit on S-box mirrors after return from LMA, posted by Loïc Amoudry at Optical room about lasers and optics
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| Cleaning on dirty surface shows something is deposited on the surface. Cleaning displaces and removes part of the deposit. |
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Damaged mirrors test, posted by Alice Renaux at Optical room about lasers and optics
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Today with Dorian we tested three mirrors with which we previously haven't been able to obtain any resonance or optical beating :
- C16111/11 : The mirror looks normal under a microscope, apart from a few inclusions and maybe a small scratch towards the edge. We tested it
with a 161186 M1 mirror and we weren't able to obtain any optical beating on the cavity's mirrors or resonance. |
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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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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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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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D-shape mirrors positionning status, posted by Ronic Chiche at Optical room about mechanics | lasers and optics | detectors and electronics
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summary:
- the motors used to move the D-shape are the Newport Picomotors 8303-V
the sensitivity is roughly 30nm/step |