NAOJ GW Elog Logbook 3.2
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NaokiAritomi - 22:17, Thursday 03 October 2019 (1691)
Squeezing and phase noise when filter cavity is locked
[Aritomi, Yuhang]
First we measured squeezing when filter cavity is locked/unlocked (Pic. 1). We expected more squeezing since we improved reflectivity of dichroic mirror by 4%, but squeezing level is still around 6.1dB when filter cavity is unlocked. Squeezing level when filter cavity is locked/unlocked is similar, but phase noise seems suppressed when filter cavity is locked.
Here are some information of this measurement.
| green power (mW) | OPO temperature (kOhm) | p pol PLL (MHz) | Demodulation phase of CC2 (SQZ) (deg) | Demodulation phase of CC2 (ASQZ) (deg) |
| 40 | 7.19 | 165 | 105 | 135 |
CC error signal
CC1: 87.2mVpp
CC2: 144mVpp
Then we measured CC1,2 phase noise when FC is locked/unlocked (Pic. 2,3). CC1 phase noise doesn't change so much, but CC2 phase noise is suppressed at high frequency when filter cavity is locked. One problem is that 70kHz large peak appears when filter cavity is locked. It might come from piezo of main laser.
Images attached to this report
