piezo actuation range, posted by Aurélien Martens at Optical room about lasers and optics | detectors and electronics
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A 10V applied on the laser piezo was found to induce a frequecny change of about 5kHz, compatible with expectations from the piezo sensitivity. this
was measured by a freqeuncy analysis of the signal produced by the laser itself on a photodiode det10a
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Finess and coupling measurement, posted by Blanc at Optical room about lasers and optics | detectors and electronics 
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We did the measurement of the Finess and coupling with the NKT, with 2 EOM, without AOM (so the lock signal is noisy), on the burst line.
For the coupling, we have the same value as with the GHz locked on the burst line too, which is around 20 percent.
it seems this low coupling comes from the geometrical coupling as we observed an incoming beam bigger than the cavity mode on the cameras. |
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Setup and measurements, posted by Blanc at Optical room about lasers and optics | detectors and electronics
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To summerize the results of this week :
We made the setup in attachement 5 and align it to have the good mode in the cavity (TEM00).
With the good alignment, we found the lock of the GHz, in attachement 1. We used the motors in the cavity to position very precisely the mirrors |
Phase noise measurement of the Amplitude MIKAN, posted by Ronic Chiche at Optical room about lasers and optics | detectors and electronics
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MIKAN phase noise and RIN measurements:
Ronic
Chiche wrote:
Coupling into a 50-50% fiber coupler using the Thorlabs XYZ table |
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Cameras Calibration, posted by Kevin Dupraz at Optical room about lasers and optics | detectors and electronics
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Kevin
Dupraz wrote:
After installing cameras the actual calibration are : |
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Cameras Calibration, posted by Kevin Dupraz at Optical room about lasers and optics | detectors and electronics
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After check a mistake has been found on the magnification. This seems to be the good calibration (feel free to cross check). The projection of the 2mm
hex is attached
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input and output power of the AOM 50MHz, posted by Blanc at Optical room about lasers and optics | detectors and electronics
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Input power of the AOM :
150mW
output power of the AOM : |
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Différence de fréquence Tangor/Lockline, posted by Blanc at Optical room about lasers and optics | detectors and electronics
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- On a observé que le fondamental du Tangor et celui de la Lockline n'étaient pas situés à la même fréquence.
Avec la différence de tension donnée par le piezo entre les deux et le déplacement du piezo en fonction de la tension appliquée
donnée par sa datasheet (150 V pour 20 µm), on obtient un écart de fréquence de 121 MHz [Image 1]. |
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Alignment using Helium Neon Laser , posted by Manar Amer at Other about lasers and optics
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| 05 April 2021 : A rough alignment of the cavity was done using the Helium Neon Laser. |
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Alignment using Koheras , posted by Manar Amer at Other about lasers and optics 6x
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Following the Helium Neon Alignment + change in the distance between the mirrors to be; M3-M4 = 90.5 mm , M1-M2 = 80.2 mm -→ The alignment
using the Koheras CW laser is done.
Additional components used:
for monitoring beam : Photodiode (power of beam), Beam Profiler (shape, position, power |
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Mode observed and cavity Lock , posted by Manar Amer at Other about lasers and optics
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** Following up from yesterday an observation about the TM00 mode : it has been seen with similar dimensions and its position is the same, this was before
restarting the temperature regulator.
--> after restarting the temp. regulator |
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Theoretical Finesse, Gain and Coupling, posted by Ronic Chiche at Optical room about lasers and optics
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For spherical mirrors M3 and M4 (batch C117I054) the reflectance (R) is around 99.9987% (if T+R=1 => T=13ppm)
For plan mirror M2 (batch C217G054) the reflectance (R) is around 99.9977% (if T+R=1 => T=23ppm)
(1) => For plan mirror M1 (batch C217H023) the reflectance (R) is around 98.96% and transmittance (T) is around 1.14% (T=11400 ppm) |
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Mode observed and cavity Lock , posted by Manar Amer at Other about lasers and optics
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New configuration is made. The new mode observed in NF_Trans is the following :
Manar
Amer wrote:
** Following up from yesterday an observation about the TM00 mode : |
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Polarisation Results of the NKT, posted by Blanc at Optical room about lasers and optics
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I made many tests about polarization and we can see some points thanks to the following figures :
1- The ellipsicity of the NKT is near to 0 (between -0,2 and 0,2) which means the polarization is rectilinear horizontale (attachement 1).
2- The power of the NKT has no influence on the polarization, verticale or horizontale (attachement 2 and 3). |
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Polarisation Results of the NKT, posted by Blanc at Optical room about lasers and optics
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To have the polarisation, we must have 1 value because the laser in entry of the system has 1 polar. Due to that, the graphe of the ellipticity is not
true, it is the mean value on the following table which shows the ellipticity and the polarization.
Blanc |
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Ring light in the cavity, posted by Blanc at Optical room about lasers and optics
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We put a diaphragm in the input beam but it doesn't work to suppress the ring light only but it attenuates the whole transmitted beam (cavity mode
and ring light) viewed on the camera. |
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Polarization Results in transmission, posted by Blanc at Optical room about lasers and optics
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After data processing, I finally find the polarization in transmissin of the FPC. As you can see below, the polarisation is not linear but elliptical.
The four ellipsies are here due to having not enougth parameters to extract with certainty one ellipse. |
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Reflection Line Polarization Measuremet, posted by Manar Amer at Optical room about lasers and optics
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With the help of Ronic the cavity was locked in preparation to measure the polarization of the reflection line when the cavity is locked (measurement
when it is not locked was done before)
the purpose is to compare the two measurements (locked vs not locked) |
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Locking with fast analog loop on AOM, posted by Ronic Chiche at Optical room about lasers and optics
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in addition to the standard locking scheme with the GHz laser PZT,
we added an AOM after the PDH modulation EOM and we drove it with an FM modulated signal generator (FMDev = 2.4MHz) seeded by the error signal.
(we didn't put a 50ohm plug to adapt the error signal coming from the PDH box, otherwise, it is too much smaller) |
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Amplitude GHz oscillator phase noise with PZT effect, posted by Ronic Chiche at Optical room about lasers and optics
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3 phase noise measurements made on the Amplitude GHz oscillator with different PZT configurations :
- black curve: PZT connector is open
- green curve: PZT connector is shorted by 50 ohms |