NAOJ GW Elog Logbook 3.2
[Aritomi, Yaochin]
We measured squeezing and anti squeezing with new faraday to estimate loss and phase noise.
| green power (mW) | MZ offset | OPO temperature (kOhm) | p pol PLL (BAB) (MHz) | BAB maximum (V) | CC2 demodulation phase (SQZ) (deg) | CC2 demodulation phase (ASQZ) (deg) |
| 0 | 7.18 | 265 | 0.19 | |||
| 20 | 4.1 | 7.17 | 190 | 0.888 | 85 | 165 |
| 25 | 4.19 | 7.16 | 160 | 1.09 | 85 | 165 |
| 30 | 4.29 | 7.18 | 180 | 1.46 | 90 | 160 |
| 35 | 4.38 | 7.18 | 175 | 2.12 | 100 | 155 |
| 40 | 4.5 | 7.19 | 180 | 3.04 | 110 | 155 |
| 45 | 4.58 | 7.19 | 170 | 3.68 | 115 | 150 |
| 50 | 4.68 | 7.19 | 160 | 4.72 | 120 | 150 |
| 55 | 4.78 | 7.2 | 165 | 6.24 | 125 | 145 |
| 60 | 4.88 | 7.2 | 160 | 7.68 | 130 | 140 |
| 65 | 4.98 | 7.2 | 160 | 10.1 |
Attached picture shows the result. Loss is 25.4% and phase noise is 21.4 mrad. Compared with previous measurement, we have 4.5% more loss. We should have 3% more loss from faraday and HWP, but we should have ~3% less loss from dichroic mirror (entry 1613). So this 25.4% loss is higher than we expected. Maybe we have worse visibility after installation of faraday. We'll check visibility tomorrow.
If I remember correctly, after improving reflectivity of dichroic mirror, squeezing level didn't change. It is also better to check the reflectivity of dichroic mirror again.
Good news is that even though we turned on lasers today, we have only 21.4 mrad of phase noise and squeezing spectrum is very flat with new faraday.
