IOO (Laser Bench)
masayuki.nakano - 23:24, Sunday 05 August 2018 (5714)
The PMC and high power laser works on the first week of August.

[Guiguo, Nakano]

We locked the PMC with the new high power laser!

1. High power laser beam profile re-measurement.

As reported in klog5638, the beam profile of the output laser from the fiber amp. was measured. However, I found that the thermal lens effect of the ND filter put on the measurement path was so large that the result is not reliable. I re-measured the beam profile without an ND filter. The result is attached. The beam waist size and the position is as follows:
Beam waist: 340(30) um for the horizontal axis, 360(30) um for the vertical axis
Beam waist position from the collimator lens: 85(5) cm for the horizontal axis, 85() um for the vertical axis

2. Mode match calculation for the PMC

I calculated the mode matching lenses for the PMC. The result of the jammt is attached.

3. Installation of the FI and the WPs for the high power laser

I installed the Faraday isolator (IO-10-1064-HP, thorlabs) and wave plates. The transmittance of the FI is about 92 % (I forgot the number to bring from the PSL. I would report later), and it is consistent with the datasheet and the experiment in Hongo.

4. Mode matching and the locking the PMC

I installed the mode matching lenses and aligned the PMC. I succeeded to lock the PMC, but the mode matching seems not good. I would work on it next week. And the control loop is not optimized yet. Also, the measurements of the FSR, the gouy phase, and the modulation index of the sidebands have to be done.

 

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To do list

- Mode matching
- Transmittance measurement
- OLG measurement of PMC
- FSR measurement. I guess that we can measure by using the sideband since the EOM is not resonant type and the modulation index seems enough to see the resonance of the sideband.
- Gouy phase measurement.
- Cavity pole measurement. Now we have the AOM and it can be used to measure the cavity pole to cross-check the previous measurement.
- Noise budget. We have the PEMs, and can measure the coherence with those sensors.