NAOJ GW Elog Logbook 3.2
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NaokiAritomi - 12:22, Sunday 01 September 2019 (1587)
Additional loss measurement
To confirm the result of loss and phase noise, I measured squeezing and anti squeezing with different loss. The way to inject additional loss is to put HWP in squeezing path and rotate the polarization. The loss can be estimated by measuring the visibility. I assumed mode matching is 99% during this measurement.
Visibility parameter
LO: 1.92 V
BAB: 0.156 V (HWP 0deg)
DC offset: 8mV
Visibility: 99% (HWP 0deg)
The result is as follows (attached picture).
| HWP angle (deg) | Vmax (V) | Vmin (V) | V_BAB (V) | Additional loss | squeezing (dB) | anti squeezing (dB) |
| 0 | 3.2 | 1.04 | 0.156 | 0 | 5.45 | 15.13 |
| 10 | 3.06 | 1.18 | 0.116 | 0.256 | 3.29 | 13.9 |
| 20 | 2.8 | 1.44 | 0.061 | 0.609 | 1.43 | 11.19 |
| 30 | 2.48 | 1.78 | 0.021 | 0.862 | 0.29 | 5.04 |
I fitted squeezing level with 3 variables which are injected squeezing and loss and phase noise. The result is injected squeezing = 16.3dB, loss = 25%, phase noise = 23.8 mrad. This is consistent with previous loss and phase noise measurement.
Images attached to this report
