unsuccessful telescope design :-(, posted by Ronic Chiche at Optical room about lasers and optics 
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we wanted to calculate the right telescope with 2 spherical lenses.
1) we have the FP cavity mode size which is 0.58mm at the input mirror and 0.7mm at the output mirror.
2) we planned to measure the laser beam at the output of the amplifier working at P=1W (2nd stage ON only). |
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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). |
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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new setup for the 160MHz Menhir oscillator, posted by Ronic Chiche at Optical room about mechanics | lasers and optics | detectors and electronics | software
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from the begining of the week, Xinyi, Aurélien, Viktor and myself started to install a new setup for the Menhir 160MHz oscillator.
the goal is to rich a record power in the FP-cavity.
- the 160MHz Menhir oscillator has been injected in a fiber. |
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new cavity, posted by Alice Renaux at Optical room about lasers and optics
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Yesterday, we changed the M1 mirror to a 161185 Gamma Factory mirror of transmission 460ppm, the cavity
finesse is now 13360.
We managed to lock it today. |
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new cavity, posted by Alice Renaux at Optical room about lasers and optics
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The 2-mirrors cavity has 460ppm of transmission for M1 and 10ppm for M2 which should exhibit a Finesse around 13400.
Today, we managed to lock the NKT laser (with an AOM for fast feedback) onto the cavity, and we made 5 Finesse measurements with the modulation
technic : 14151, 13847, 13968, 14604, 13892 with an average around 14000 => LW = 216MHz/F ~ 16kHz. |
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liPower storage In Cavity, posted by Manar Amer at Optical room about lasers and optics
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After changing the mirror M1 and cleaning the 2 mirrors
They were placed in the cavity box (avoiding touching the mounts to not affect the alignment and placing the mirrors as close to the previous
position) |
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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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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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first data with 3A on the 3rd stage, posted by Ronic Chiche at Optical room about lasers and optics
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Today, at 3A on the 3rd stage, we saw some HOM effects.
the transmissions is about 100mW which corresponds to 30kW inside cavity.
we tried to play with D shape motors but without success. |
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first data with 3A on the 3rd stage, posted by Ronic Chiche at Optical room about lasers and optics
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2 pictures :
typical beam with HOM
typical beam after moving the D-shape motor : no more HOM |
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first attempt to lock, posted by Ronic Chiche at Optical room about mechanics | lasers and optics | detectors and electronics
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With Alice, we installed the EOWaves oscillator to be locked on the FP-cavity (T1 ~ 2500ppm, T2 ~ 10ppm => F ~ 2500)
FSR = 216MHz => LW = 86kHz.
We installed the PDH box, and we got some error signal, but the shape of the transmission signal and error signal is a bit strange... |
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chiller for CELIA amplifier, posted by Aurélien Martens at Optical room about utilities
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The chiller of CELIA amplifier has been moved from the corridor to the changing room in front of PLIC.
It was not functionning well (quick drop of flow below 0.9l/min). After several cleanings of the filter, shorting the water circuit a stable
2.1l/min flow was obtained. Then the water circuit was elongated to go close to the amplifier but not into it. Allowing to get about 1.3l/min stable. Now |
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chiller for CELIA amplifier, posted by Aurélien Martens at Optical room about utilities
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today, temperature of the chiller has been set to 23°C.
measured temperature in the chiller reaches 23°C after approximatively 10 minutes
Aurélien |
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analysis of stored and reflected power, posted by Ronic Chiche at Optical room about lasers and optics 6x
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the 10th of January, we increased the power of the amplifier to study the cavity transmitted and reflected power signals.
analyzing the noise transfer functions of transmitted and reflected power one could deduce the Finesse of the cavity.
the power of this technic (if it is confirmed) does not depend on the decay time of one signal which depends on the speed of the cut off but on |
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analysis of stored and reflected power, posted by Ronic Chiche at Optical room about lasers and optics
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A chart which summarizes the data we have or we can estimate.
in orange, the case 1, where we suppose the initial cold Finesse is the one measured by modulation technique in December 2019 (F=20.8k). |
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analysis of stored and reflected power, posted by Ronic Chiche at Optical room about lasers and optics
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with this Finesse around 22-23k, the technique comparing TRANSMISSION and REFLECTION signals doesn't work, even in taking into account individual
photodiode time responses.
It seems that the cavity is not completely stationnary and the shapes are not comparable easily with just a Low Pass Filter related to the Finesse. |
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amplifier, posted by Huan Wang at Optical room about lasers and optics
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Onefive output power is 24mW now, and 2.41mW(after EOM) injected into fiber,
a injection power monitor added, 99% (2.06mW) injected into amplifier, 1% (16.1uW) monitored with photodiode DET36A/M, which
gives ~500mV DC signal on oscilloscope with 1Mohm impedanc; |