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. |
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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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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Menhir pulsed laser locking, posted by Xinyi Lu at Optical room about lasers and optics
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These days, Ronic, Daniele and I achieved stable cavity locking with the menhir pulsed laser.
- After vacuuming, the current cavity finesse is now about 23,000. The diameter of the cavity mode is w_x=2.2mm, w_y=2.7mm.
- We had to compensate for frequency drift by manually adjusting the cavity length to keep locking. |
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Menhir pulsed laser locking, posted by Xinyi Lu at Optical room about lasers and optics
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Here is a simulation of the relative FP-cavity gain vs the CEP for a Finesse of 23000 and taking into account the Menhir laser optical spectrum and several
CVBG parameters.
I added the commented Matlab code to produce this plot. |
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Menhir pulsed laser locking, posted by Xinyi Lu at Optical room about lasers and optics
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Last week, Ronic and I focused on CEP measurements of the menhir laser.
Measurements without Cavity Locking:
Direct measurement of repetition rate (Frep) with a spectrum analyzer.
Altering the laser pump current from 950mA to 850mA, Frep changed by +28Hz.
Measurement of the variation of carrier-envelope frequency |
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Menhir pulsed laser locking, posted by Xinyi Lu at Optical room about lasers and optics
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here is the code to get this last curve
Xinyi
Lu wrote:
Last week, Ronic and I focused on CEP measurements of |
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Amplified laser injection, posted by Xinyi Lu at Optical room about lasers and optics
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In the last two days, Ronic and I connected the amplifier and locked the cavity.
- We installed an iris on the output to remove a part of the pump.
- We turned on the second stage of the amplifier. When locking, the injected power is 220 mW and the transmitted power after M2 is 26 uW. |
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100W CELIA laser amplifier "how's to" document, posted by Ronic Chiche at Optical room about lasers and optics | software
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1st version of the document.
if some information is not correct or missing, give any comment by replying to this post. |
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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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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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Polarization issue, posted by Xinyi Lu at Optical room about lasers and optics
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These days, Ronic, Aurélien, Fatematuj and I have been doing some tests on polarization issue, trying to see if it is possible to obtain higher
gain under other polarization conditions.
We installed an additional half-wave plate + PBS + PD at the transmission. By rotating the waveplate of the injection laser, we can compare |
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Polarization issue, posted by Xinyi Lu at Optical room about lasers and optics
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just to add some details :
about the S and P polarization frequency shift:
the PZT scan is 10Vpp at 3.1Hz => the slope is 62 V/s because of the triangle shape of the PZT scan. |