2 mirror cavity high power experiments, posted by Xinyi Lu at Optical room about lasers and optics 
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Today, Ronic and I recorded some intracavity power and cavity mode size as shown in Fig. 1.
Coupling was calculated using the locking curve of this overcoupled cavity. Pr/Pi = 1-Cgeo*Cimp, Cimp = 1-|1-2T1/RTL|^2
We can see that the effective gain, coupling, and mode size decrease with increasing power. And the beam is constantly moving. |
high-power experiments of 2-mirror cavity, posted by Xinyi Lu at Optical room about lasers and optics
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Today, Ronic, Daniele and I redo the high-power 2-mirror cavity experiments, and the results are shown in the table (Figure 1 and Excel 2 ).
- The intracavity power ~500kW can be obtained at 47W injection, but we then have no increase or even a decrease in intracavity power when
increasing the injection power, and the coupling is decreasing. It looks like the saturation power of the current device. |
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high-power experiments of 2-mirror cavity, posted by Xinyi Lu at Optical room about lasers and optics
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here is a Matlab code to try to optimize the telescope for a hot cavity,
taking into account the thermal lens in the coupling mirror.
from that code, one can deduce using the "Gaussian Beam" software (using the attached xml file) an optimized telescope with 100% geometrical |
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high-power experiments of 2-mirror cavity, posted by Xinyi Lu at Optical room about lasers and optics 6x
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Here's a summary of our experiment last week:
The initial telescope position: 920 mm (f=+250mm) and 1148 mm (f=-150mm) from the amplifier output.
Mon May 6: We moved the concave lens 0.5mm closer to the cavity. |
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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 |
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Menhir 160MHz laser, posted by Alice Renaux at Optical room about lasers and optics
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The Menhir 160MHz has been put back in place on the CELIA amplifier setup. Its output power is measured to be 150-160mW with an attenuator as expected.
Its spectrum is available in "spectre_avant_cvbg.xlsx" and "spectre_avant_cvbg.png".
The pulses are stretched by means of a CVBG. Their spectrum is available in "spectre_apres_cvbg.xlsx" and "spectre_apres_cvbg.png". |
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optical table cleaning, posted by Ronic Chiche at Optical room about utilities
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this morning with Alice and Daniele, we removed all the optics elements and equipments from the SBOX optical table and started to clean it.
the dust meter count 0 on all particle sizes after the cleaning.
we observed a small part of the SBOX which seems to be oxydised (see picture). |
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optical table cleaning, posted by Ronic Chiche at Optical room about utilities
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this afternoon, we checked the dust meter which is at 0 for 1 and 5µm dust particles but ~ 2000-3000 for 0.3µm particles.
we opened the two top panels to let the air flow clean the inside of the vessel.
we observed some other minor oxydised regions (than the one taken in picture) on the external parts of the inox panels but at first sight, nothing |
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optical table cleaning, posted by Ronic Chiche at Optical room about utilities
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now, it seems the table is clean enough (dust meter counts 0 particles) to install a 2 mirrors FP-cavity.
Ronic
Chiche wrote:
this afternoon, we checked the dust meter which is at 0 for 1 and |
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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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Installation of the avalanche photodiode, posted by Ronic Chiche at Optical room about lasers and optics | detectors and electronics
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After installing the 2nd EOM, we had some trouble to be able to lock again.
One possible reason was the very low signal level in transmission, which is important to trigger the locking system (and stop it).
See the Alice post for details, but we were able to measure only once the Finesse of the cavity at around 2600. |