FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics 
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Note the direction of injection is M1 - M2 - M3 - M4
P1 - S2 - S3 - P4 |
FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics
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The alignment is on hold until next week 17th - 18th Jan
an Alignment attempt will be done when the ring part close to the FP cavity is opened.
Manar |
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FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics
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***** Continuation of the alignment ---- FP Cavity Open --- ****
The cavity was put under outer pressure and was opened for the alignment
The alignment was done using CW koheras infrared laser and the inside mirrors irises |
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FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics
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Yesterday, we did the alignment again using Iris and beam profilers to obtain a more precise result.
at the end of the alignment procedure, we successfully obtained the beating modes.
the geometrical alignment seems good (weak odd modes) but we could need to put a telescope on the Koheras line as the beam size seems quite different |
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FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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Installed and inputs:
CW laser ; power = 101 mW
PDH ;
at output
Low pass filter 50 ohm DC-1.9 MHz
at
input
freq = 8.4 MHz , Ampl = 1.2 V , phase = 160 /
voltage = ~ 6 V
EOM |
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FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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This afternoon, I did some alignment of the injection mirrors with a fast scan on the LaseLock to get a regular transmission photodiode signal.
the coupling increased to 10-15%
I got a first lock of the cavity only with the PZT. |
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FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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This morning with Manar, we installed the AOM+RF amplifier and the associated fast feedback loop.
Now the locking with the Koheras is good with a coupling of 20%.
Tomorrow is dedicated to the measurement of the Finesse.... we will have to add the 2nd EOM. |
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FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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Adding Oscilloscope images
delocked + locked intervals showing the 20% coupling
lock when the housing panels are closed + airflow on .
lock
when the housing panels are closed + air flow at lowest setting
an additional factor to the PZT voltage sensitivity |
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FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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Ending alignment series !!
Manar
Amer wrote:
Adding Oscilloscope images |
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FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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As it can be seen on the first plot, even with a good locking (good reduction of "high" frequencies noise: we had better locking than on the
picture) we still have very low frequency (~ 1Hz) fluctuations
these fluctuations prevent having a good measurement of the Finesse and they need to be understood. |
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Cavity Lock and Finess measurment , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics 6x
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This morning, me and Ronic managed to obtain the FSR and image of the finesse which is to be analyzed.
Adding:
Beam Image at P4 propagation, no lens is added.
Image of the Finesse on Oscilloscope
more information to |
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FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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The fluctuation problem has been solved.
It was simply the new scheme to inject 2 RF frequencies in a single EOM.
It maybe produces some standing waves in the EOM RF input and creates some phase noise. |
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Cavity Lock and Finess measurment , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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to measure the Finesse, instead of having 2x EOM for the PDH and for the modulation sweep, I simply used 2x generators coupled with DC-blocks
to a T connector (SMA) screwed directly on the EOM input. |
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Cavity Lock and Finess measurment , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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After changing the way of injecting modulation for PDH and modulation for FSR scanning (we split the modulations to 2 different EOMs), the locking
is very stable and we can measure the Finesse. |
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Cavity Lock and Finess measurment , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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one thing which could reduce the Finesse is the L-shape metal piece if it is slightly inserted in the FP-cavity mode path.
understanding where this L-shape effectively is is not easy... some pictures are attached.
Manar |
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Cavity beam Image , posted by Manar Amer at ThomX igloo about lasers and optics
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Updated beam image after change on the mode axis.
Taken after P4. |
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Current Installed Setup, posted by Manar Amer at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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| Attached is the current setup in ThomX |
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Alphanov amplifier Beam Profile, posted by Manar Amer at ThomX igloo about lasers and optics 8x
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Today: Manar, Ronic and Aurlien started the study of the beam profile of the alphanov amplifier at high power.
The setup shown in the image shows how the power is reduced by using Anti-reflective mirrors,
pick up 1 : Anti-reflective coating on both sides , pick up 2 : Anti-reflective coating on one side and High |
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Alphanov amplifier Beam Profile, posted by Manar Amer at ThomX igloo about lasers and optics
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Manar
Amer wrote:
Today: Manar, Ronic and Aurlien started the study of the beam profile |
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Alphanov amplifier Beam Profile, posted by Manar Amer at ThomX igloo about lasers and optics 6x
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Adding the fitted beam in 1D in Horizontal and vertical axis.
for 10% to 60%
Manar |