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. |
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 |
Alphanov amplifier beam profile Data , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics 8x
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Adding the schematic of the measurements.,
the 4° Beam Deviation, AR Coating ( B coating)
The 3 data points taken of the beam profile are fitted in Gaussian Beam with taking the beam waist at the output of the compressor box. |
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Alphanov amplifier beam profile Data , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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This Morning with Victor the amplifier was turned on @ 20% amplification (output ~ 9 W ) for approximately 3 hours and no error appeared.
I took data of the beam profile at different points without a lens after the 2 wedges
@ 0% (only pump beam), output ~ 300 mW (taken from previous data) , output after 2 wedges 2.2 uW |
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Amplifier Beam Profile over time , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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This morning, with Ronic, we opened the compressor box to observe if there is any misalignment of the mounts or the CVBG's
a comparison slide between the Beam Profile over time and measurements we have taken, is included.
we noticed
today that the images need a rotation, and I took the assumption we did not rotate last year and did the rotation of the previous images.
Comparing |
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Amplifier Beam Profile over time , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics 10x
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This morning we took data of the beam profile at 4 different points to see the evolution of
the beam shape
divergence
over distance for all amplification percentages
Data plotted for the distance vs radius for all and divergence in rad is extracted and plotted as a variation of amplification power. |
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Amplifier Beam Profile over time , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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Information about today's work is added to logBook !!
Manar
Amer wrote:
This morning we took data of the beam profile at 4 different points |
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Cavity Alighnment , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics 9x
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Last week, with Ronic and Victor we aligned the cavity using CW laser (Koheras)
we have also installed 4 mirrors in the cavity with the best theoretical qualities (serial number and images included)
The
Plan ULE mirror P4 thickness was not compatible with the piezoelectric mount. We had to install a metal spacer behind the mirror |
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CW FP Cavit lock , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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Yesterday morning we locked the cavity on a strange mode in the cavity (we call it mode, but not sure what it is ??)
we also managed to lock on a higher order mode 02
we get an estimated 30% coupling (expected value), and note that we have not installed a telescope yet. |
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CW FP Cavit lock , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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This morning with Daniele and Viktor,
- we confirmed the "potato" mode was well centered on the injected beam and was not due to some misalignment of the injected beam compared
to the cavity axis. |
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FP Finesse measurement using CW, posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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This morning, with Ronic and Daniele, we locked the cavity again (The lock was relatively easy and stable during the reading of the finesse)
We took 2 reading of finesse
1st : @ 33.2808 MHz (what the cavity length was at) : Finesse = |
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PW laser Injection into cavity , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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Yesterday,
we installed the second high power reflecting mirrors at the output of the amplifier.
We aligned and installed a telescope
that has adjustable distance between the 2 lenses of -100 mm, and + 200 mm, with approximate diameter at the injection window of ~ 4.5 mm.
Amplifier |
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PW laser Injection into cavity , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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On Monday with Daniele,
we did full characterization of amplifier beam @ 10% amplification, adjusted the telescope accordingly
and injected into the cavity aligned and improved on the fundamental mode.
On Tuesday with Daniele and Kevin
I
added a low pass filter between 1 - 1.9 MHz on the reflected signal, to reject the oscillator signal (33.33 MHz)
removed the external resistors |
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PW laser Injection into cavity , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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Added Note: the coupling we get is at low power, only preamplifier is on (~ 300 mW)
was done at the end due to excitation of higher order modes.
Wanted to improve the fundamental first, then increase the power. |
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PW laser Injection into cavity , posted by Manar Amer at ThomX igloo about lasers and optics | detectors and electronics
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Today with Ronic and Daniele we attempted to lock the cavity, but the alphanov amplifier did not turn on because of an error in MMD3 (related to the
third stage)
the new error is having the MMD3 error show on the alarm window of the LAL software, and having the Alarms on the line 3 of the alphanov software |
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work with HV voltage on the Laselock, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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presently, the voltage on the laser PZT is 0-10V, but during the several runs we did, this voltage is too low to compensate low frequency fluctuations:
we need to change often the motors position implying a cavity lock loss.
we have to check if running the laser PZT with the HV output of the Laselock is possible without too much additionnal noise. |
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work with HV voltage on the Laselock, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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Yesterday, I checked the 2 output HV channels of the LaseLock : they work properly but the noise is bigger than the low voltage outputs
~ 1mV rms on 0-10V outputs
~ 8 mv rms on 0-100V output |
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Fast feedback loop between laser and FP cavity, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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today, we tried to lock the FP cavity with the Smaract motors ON (with option -LV).
we know the Smaract controllers produce some noise and the lock is very bad or impossible when the controller in ON (whatever the displacement mode
is : closed or open loop, or piezo scan). |
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Fast feedback loop between laser and FP cavity, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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today, after the several unsuccessful attempt yesterday to get an improvement in the lock,
we decided to "rebuild" the error signal electronics block by block and step by step :
the scheme is basically : |