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 |
Laser Menhir reinstallation + CVBG + fiber injection, posted by Ronic Chiche at Optical room about lasers and optics 
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The lab purchased the Menhir laser @ 216MHz.
it has been sent back to Menhir photonics for inspection, and then is now at lab.
it has been reinstalled to the SBOX setup with injection in a CVBG for pulse stretching before amplification. |
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Larger beam size & Spectrum, posted by Xinyi Lu at Optical room about lasers and optics
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- We re-measured the gain before moving the mirror. Gain ~9000 was achieved at 3A, but as the power increased, the gain dropped and was difficult to
optimize. In fact, we found that each day the gain was a little higher than the previous day.
Amp current (A)
Injection power (W)
Circulating |
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Koheras CW laser lock on FP cavity, posted by Ronic Chiche at Optical room about lasers and optics | detectors and electronics
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I locked the Koheras CW on the FP cavity but the lock was pretty noisy and very difficult to acquire.
I tried to produce some modulation sidebands close to 216MHz to measure the Finesse but the power loss was very small so, the signal to extract
the Finesse would be unreadable ! |
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KBox Alignment , posted by Manar Amer at Optical room about lasers and optics 7x
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Starting with the alignment of the KBox using CW Koheras.
The size of the CW output from the collimator at 1 meter from is ~ 2.4 mm, to be adjusted with lenses to match the cavity !!! (attached
image) |
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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. |
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Installation of D-shaped mirror / Alignment, posted by Manar Amer at Optical room about lasers and optics | detectors and electronics
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To prepare for the amplifier. I installed the D-shapped mirrors after cleaning (using aceton and ethanol) between the cavity 2 mirrors.
Before closing, I observed the back reflection from M1 (injection mirror). both the injection and reflection lines were off, due to that there
was an internal reflection hitting the walls of the cavity. |
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Installation of D-shaped mirror / Alignment, posted by Manar Amer at Optical room about lasers and optics | detectors and electronics
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The D-shaped mirrors are installed properly and not cutting the path of the beam.
The cavity has been aligned again and 00 modes beating observed, and external reference points has been placed.
Manar |
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Install new mirrors, posted by Xinyi Lu at Optical room about lasers and optics
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Today, Ronic and I installed the new mirrors and got resonance. We can see the oscillations in this high-finesse case. We haven't carefully
optimized the alignment. Coupling efficiency is about 15% and the cavity can be locked.
Tomorrow we will optimize the alignment and locking, and measure the finesse. |
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Install new mirrors, posted by Xinyi Lu at Optical room about lasers and optics
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- In the last two days, Ronic and I installed new mirrors after cleaning the environment, and locked the cavity.
- We added an AOM to feedback on the high-frequency noise, but the locking condition was still not good enough. We found out that the signal generator
available for this AOM has a long delay time (3 us), which may lead to low feedback bandwidth. So tomorrow we will use another AOM and signal generator |
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Install new mirrors, posted by Xinyi Lu at Optical room about lasers and optics
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- Today, Ronic and I changed the signal generator to a low-noise one (with a delay time of only 0.5 us). Then we moved the D-shaped mirrors, optimized
the alignment and locking. We re-measured the finesse and it is 16,760. It improves but not much.
- Tomorrow, we will clean the environment, open the cavity, and use UV light to see if there is any dust on the surface of the mirrors. |
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Install new mirrors, posted by Xinyi Lu at Optical room about lasers and optics
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Yesterday we checked the mirrors with UV light and there was some dust on the mirrors, especially M2.
Today, Daniele, Ronic and I removed M2 and observed it with a microscope. It was indeed dirty, despite we were careful in installing it before.
After that we cleaned it with alcohol and mirror paper, then with a spin coater and pure water. After cleaning, we observed it again and it was much better |
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Install 2-mirror cavity, posted by Xinyi Lu at Optical room about lasers and optics
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Today, Viktor and I started installing the two-mirror cavity.
- Firstly, we cleaned the environment and the dust counter showed good cleanliness
- After opening the cavity we tried to determine the source of the strange spot with a laser detection card and found that the beam was |
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Install 2-mirror cavity, posted by Xinyi Lu at Optical room about lasers and optics
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Today Viktor and I completed the installation of the two-mirror cavity and managed to lock and measure the finesse.
- The finesse is 36k now (see figure 1). For the designed value of the mirror, the expected finesse is ~50k.
- The diameter of M2 transmission is 1.67 mm,1.65 mm (see figure 2). |
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Injection at the amplifier current of 2 A, posted by Xinyi Lu at Optical room about lasers and optics
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Today, Ronic and I optimized the locking at the amplifier current of 2 A and obtained ~ 21 kW inside the cavity.
- When all the iris open, the injected power is 10 W and the coupling is ~ 40%, corresponding to an effective gain of 2,100 and
a full gain of 5,250. But the coupling may not be the true value because there is a large spot around the output beam. |
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Impacts on mirror's surface, posted by Loïc Amoudry at Optical room about lasers and optics
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All the mirrors show impacts on there surface (some of them do not show deposit). Does it come from experiments or fabrication ? Are these holes
or bumps ? |
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Images of ThomX mirrors , posted by Manar Amer at Optical room about lasers and optics
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Under the microscope,
the spherical mirrors show the deposit of metal dots on the reflecting surface and not on the back of the mirrors
The mirror with fewer spots near the center was used in the setup. |
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Images of ThomX mirrors , posted by Manar Amer at Optical room about lasers and optics
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Mirror images in the previous log showing the metal deposit of the coating of the spherical mirrors
(not sent by mail due to large size of images)
Manar |
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High power experiments (550kW), posted by Xinyi Lu at Optical room about lasers and optics
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- Today we moved the position of the D-shaped mirror at 6A. When motor1 (vertical) is 0.2mm away from the spot, the power in the cavity rises from 457kW
to 483kW. Gain=8407 is similar to that at low power (Gain=8511). So the D-shaped mirror lost some of the gain in the previous experiments. At 4A and 5A
we did not move the D-shaped mirror. (Figure 1) |
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High power experiments (520kW), posted by Xinyi Lu at Optical room about lasers and optics
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Yesterday, Ronic, Xing, Qili and I achieved a more stable 520kW power at 7.5A (71W injection) by optimizing the alignment and locking parameters. (Figure
1)
- The cavity can be stable locked when airflow is on. At 7.5A, the pump temperature is about 28℃. The chiller temperature didn't |