Coupling efficiency improvement, posted by Xinyi Lu at Optical room about lasers and optics 
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- Recently we have focused on improving the coupling efficiency. Without the telescope, the original coupling efficiency was less than 3%.
- I measured the parameters of the incident CW laser using both a HASO wavefront sensor and a CCD. I designed and installed the telescope, but the
coupling efficiency still did not improve. |
Coupling efficiency improvement, posted by Xinyi Lu at Optical room about lasers and optics
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- We got 30% coupling efficiency by installing a set of telescopes, adjusting the polarization and optimizing the alignment. The diameter of the cavity
mode is about 2.1mm.
- Ronic and I successfully locked the optical cavity. Tomorrow we will test the FSR and finesse. |
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Coupling efficiency improvement, posted by Xinyi Lu at Optical room about lasers and optics
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- These days, Ronic, Fatematuj and I measured the beam parameters of the output of the third-stage amplifier.
- We used 2 wedges and reflection filters to reduce the intensity on the CCD.
- We measured multiple points at pump current of 2 A (output power ~10 W). The waist diameter of the output is w_x = 792.26 |
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Coupling efficiency improvement, posted by Xinyi Lu at Optical room about lasers and optics
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Today, Ronic and I installed the new telescope and locked the cavity.
- We locked at the amplifier current of 1 A and obtained 32% of coupling. (see Figure 1)
- The telescope was designed for a current of 2 A (output power ~10 W). To inject this power, we need to add some filters to devices. |
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Coupling efficiency improvement, posted by Xinyi Lu at Optical room about lasers and optics
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- Today, Ronic and I locked at the amplifier current of 2 A and obtained ~60% coupling after optimizing the CEP (see Figure
1).
- The injected power is 10 W at 2 A. We measured only 14 kW inside the cavity, which corresponds to an effective gain of 1,400 and a full gain |
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Cleaning of Mirrors, posted by Xinyi Lu at Optical room about lasers and optics
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Today Daniele, Ronic and I cleaned the mirrors and locked the cavity. However, the finesse was only 13,000 because of the not clean enough environment
and not pure enough alcohol and water.
We will carefully clean the environment, clean the mirrors again with pure alcohol and water and measure the finesse when I return. If it doesn't |
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Cleaning of Mirrors, posted by Xinyi Lu at Optical room about lasers and optics
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- Today we cleaned the environment and put the spin coater and microscope inside the airflow.
- Tomorrow, Daniele and I will clean the mirrors one by one using pure alcohol and water, and measure the finesse each time. If it does not improve,
we will clean them with plasma. |
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Cleaning of Mirrors, posted by Xinyi Lu at Optical room about lasers and optics
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Today, Daniele and I cleaned mirrors one by one using pure water, alcohol, and the spin coater. Here are the measurements of finesse each time:
1. Initial value: 14,076
2. Clean Mirror 2: 20,606 |
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Cleaning of Mirrors, posted by Xinyi Lu at Optical room about lasers and optics
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- Today, Daniele and I cleaned the cavity inside, recleaned the M2 and M4 and their mounts, optimized the locking, and the finesse is now about
25,000.
- Although it's lower than the expected 30,000-40,000, we decided to move on to the next step. In addition, the mount of M4 is |
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Clean Airflow Dust measurements, posted by Manar Amer at Optical room about detectors and electronics | utilities
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The dust meter cap was cleaned using Alcohol, and using the filter white cap the dust count was (0 Av. 10 min)
After the dust counter was hand held in direct airflow, it counted (1581 p/m3 Av. 2 min).
I tested the count also in the SAS, and it counted twice the amount ~ 4500 p/m3 |
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Clean Airflow Dust measurements, posted by Manar Amer at Optical room about detectors and electronics | utilities
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Dust measurement done today on top of the SBox average 10min
Manar
Amer wrote:
The dust meter cap was cleaned using Alcohol, and using the filter white |
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Change of the 3 ULE mirrors by 3 spare ULE mirrors, posted by Loïc Amoudry at Optical room about lasers and optics
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| First finesse measurement 20 266, FSR 133.351 MHz under vacuum |
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Cavity polarization states (Koheras), Finesse of 2 polarization states, posted by Loïc Amoudry at Optical room about lasers and optics
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Measurments of Finesse with the 2 polarization states, let's call them H (higher) and L (lower): 24500 for the H and 23500 for the L.
We checked the polarization states in transmission of the FP cavity after a PBS. The H was stronger in PBS trans and the L stronger in PBS ref.
We measured the power in reflection of the PBS and added a half WP that we aligned with the PBS polarization. Then, to get the maximum power |
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Cavity beam axis moving with power, posted by Ronic Chiche at Optical room about lasers and optics 9x
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how the cavity beam axis is moving during a lock when the cavity is hot ?
could it explain a part of the Transmission / Coupling signal decay ?
we placed 2 Basler camera, one at (30+Z) cm and the other at (85+Z) cm (Z is about 15cm) from the M3 mirror, we recorded the video during a lock |
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Cavity Lock , posted by Manar Amer at Optical room about lasers and optics | detectors and electronics | software
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Start with the cavity lock images attached, taken from last week, at start we have a coupling ~ 5% and started improving on the
alignment .
The image of 00 modes attached corresponds to the coupling seen on the oscilloscope. |
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Cavity Lock , posted by Manar Amer at Optical room about lasers and optics | detectors and electronics | software
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Current setup at SBox for locking the cavity
After spacial matching, the coupling increased to ~ 15 - 20 %
The locking was done for the fundamental mode, tried to improve the coupling with the motors, but the lock is very unstable to be investigated. |
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Cavity Lock , posted by Manar Amer at Optical room about lasers and optics | detectors and electronics | software
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Cavity locked today under vacuum and no airflow, it is stable over a long time
the alignment was improved and an increase of the transmission by 20 % from its original value
unfortunately, data from the oscilloscope was saved, but it was not in the correct format (image) to show. |
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Cavity Lock , posted by Manar Amer at Optical room about lasers and optics | detectors and electronics | software
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Closing the series for the setup
The cavity was only locked @ 133.33 MHz but the Finesse was not measured
The FSR was changed to match the new laser MENHIR 216.6625 MHz |
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CVBG stretching / Fiber Injection , posted by Manar Amer at Optical room about lasers and optics | detectors and electronics | software 7x
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Before injecting into the amplifier, the pulse needs to be stretched using a CVBG, type attached.
the CVBG is to be used at a small angle, the beam shape and spectrum after the PBS is attached.
After measuring the beam profile, a mirror was placed to direct all the power for fiber injection |
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CVBG stretching / Fiber Injection , posted by Manar Amer at Optical room about lasers and optics | detectors and electronics | software
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closing series
Manar
Amer wrote:
Before injecting into the amplifier, the pulse needs to be stretched |