Install 2-mirror cavity, posted by Xinyi Lu at Optical room about lasers and optics 
|
Today Viktor and I completed the installation of the two-mirror cavity and managed to lock and measure the finesse.
- The finesse is 36k now (see figure 1). For the designed value of the mirror, the expected finesse is ~50k.
- The diameter of M2 transmission is 1.67 mm,1.65 mm (see figure 2). |
|
Finesse measurement of 2-mirror cavity, posted by Xinyi Lu at Optical room about lasers and optics
|
- Today Daniele and I cleaned the spherical mirror by wiping it with alcohol, and the finesse increased to 47k in air.
- After vacuuming, the final finesse is about 45k. The enhancement factor is expected to be 23k.
- Then we tuned the cavity length, FSR = 216.666 MHz. Aurélien helped us to install the menhir laser of 216 MHz. |
Fiber injection, spectrum and connection of 2nd stage amplifier, posted by Xinyi Lu at Optical room about lasers and optics
|
Today, Daniele and I injected the laser into the fiber, installed the telescope, connected the second stage of the amplifier, and obtained resonances.
- The output power of the menhir laser @ 216MHz is 150mW, after CVBG is 28mW , 9.6mW injected into the fiber, and 1.6mW via AOM and EOM. This
is not far from the minimum 1mW seed power required by the amplifier. |
|
2 mirror cavity high power experiments, posted by Xinyi Lu at Optical room about lasers and optics
|
Today, Ronic and I recorded some intracavity power and cavity mode size as shown in Fig. 1.
Coupling was calculated using the locking curve of this overcoupled cavity. Pr/Pi = 1-Cgeo*Cimp, Cimp = 1-|1-2T1/RTL|^2
We can see that the effective gain, coupling, and mode size decrease with increasing power. And the beam is constantly moving. |
|
high-power experiments of 2-mirror cavity, posted by Xinyi Lu at Optical room about lasers and optics
|
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. |
|
high-power experiments of 2-mirror cavity, posted by Xinyi Lu at Optical room about lasers and optics
|
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 |
|
high-power experiments of 2-mirror cavity, posted by Xinyi Lu at Optical room about lasers and optics 6x
|
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. |
|
CELIA 100W laser amplifier repair , posted by Ronic Chiche at Optical room about lasers and optics
|
this morning with Alice, we sent the Menhir 160MHz injected in a fiber (with 6mW at the end of a long fiber) into the laser amplifier, to look for leakage
or damage in the first stages of the amplifier (the amplifier is totally off).
first of all, we checked for light scattering around the laser crate with a sensitive optical card => nothing |
|
CELIA 100W laser amplifier repair , posted by Ronic Chiche at Optical room about lasers and optics
|
this afternoon, we saw some electric cables badly connected to their power supply.
we fixed it by soldering them together and screwing the result to the power supply.
(see 1st image) |
|
Menhir 160MHz laser, posted by Alice Renaux at Optical room about lasers and optics
|
The Menhir 160MHz has been put back in place on the CELIA amplifier setup. Its output power is measured to be 150-160mW with an attenuator as expected.
Its spectrum is available in "spectre_avant_cvbg.xlsx" and "spectre_avant_cvbg.png".
The pulses are stretched by means of a CVBG. Their spectrum is available in "spectre_apres_cvbg.xlsx" and "spectre_apres_cvbg.png". |
|
Menhir 216MHz laser, posted by Alice Renaux at Optical room about lasers and optics
|
The Menhir 216MHz laser has been put back in place on the cavity table. Its output power is measured to be 160mW with an attenuator. Its spectrum is
available in "spectre.xlsx" and "spectre.png". The main wavelength is a bit shorter (1028.75nm) and the spectrum a bit narrower (4.73nm)
than expected. |
|
CELIA 100W laser amplifier repair , posted by Ronic Chiche at Optical room about lasers and optics
|
friday morning, we add a zoom call with Jerome Lhermite about the amplifier repair.
he approximately confirmed the amplifier scheme from the Loic thesis.
he suggested to: |
|
2-mirror cavity alignment, posted by Alice Renaux at Optical room about lasers and optics
|
Yesterday and today, I replaced the OEWaves CW laser with the NKT CW laser. Its screen does not display anything, so it has to be operated through the
GraphiK software.
I then re-aligned the cavity with a new adjustment adaptation tool between the mirror mounts and the irises. |
|
2-mirror cavity alignment, posted by Alice Renaux at Optical room about lasers and optics
|
The NKT laser PZT sensitivity is ~0.09pm/V of wavelength variation, which is equivalent to ~ 25MHz/V
So, the full range of the scan is roughly 250MHz (more than a FSR) for 10V.
It seems impossible to get such large resonances unless the Finesse is very low => let's try to change M1 by a spare GammaFactory plan |
|
2-mirror cavity full setup, posted by Alice Renaux at Optical room about lasers and optics
|
Today with Ronic, we changed the FP cavity's mirrors to Layertek (Gamma Factory) mirrors :
- M1 : n°161186 --> fused silica, unknown absorption, unknown diffusion, T1=2500ppm transmission planar mirror ;
- M2 : n°161182 --> fused silica, unknown absorption, unknown diffusion, T2=10ppm transmission, 5m ROC mirror. |
|
Damaged mirrors test, posted by Alice Renaux at Optical room about lasers and optics
|
Today with Dorian we tested three mirrors with which we previously haven't been able to obtain any resonance or optical beating :
- C16111/11 : The mirror looks normal under a microscope, apart from a few inclusions and maybe a small scratch towards the edge. We tested it
with a 161186 M1 mirror and we weren't able to obtain any optical beating on the cavity's mirrors or resonance. |
|
2-mirror cavity locking, posted by Alice Renaux at Optical room about lasers and optics
|
In June, we encountered some problems regarding the transmission and error signals (see images here),
looking as if the laser was switched off before the cavity was filled.
|
|
Successful lock (finally !), posted by Alice Renaux at Optical room about lasers and optics
|
Today, with Ronic, we managed to get a successful lock with the NKT laser by setting up a new PDH box from scratch (photodiode + amplifer + mixer).
Me measured the injected power (5.4mW) and the transmitted power (33µW) after a wedge (92% transmission) and a 7ppm transmission mirror,
so the intracavity power was 5.1W. We have a 950 enhancement factor for a 3100 finesse cavity, so a nominal enhancement factor of 2500. The lock was very |
|
Finesse measurement, posted by Alice Renaux at Optical room about lasers and optics
|
Today, with Ronic, we measured the finesse of the 2-mirror cavity witht the NKT CW laser.
We were able to perfrom the measurement only once, and the results of the measurement are attached to this note. We added sidebands to the laser
spectrum peak thanks to an EOM, and we sweeped the modulation frequency on a 1MHz span around an estimated FSR of 216.63MHz in 10s. We found a 82kHz linewidth, |
|
Finesse measurement, posted by Alice Renaux at Optical room about lasers and optics
|
(Finesse 2651 is consistent with that obtained from the mirrors' transmission coefficients, which is about 3100.)
Alice
Renaux wrote:
Today, with Ronic, we measured the finesse of the 2-mirror cavity |