We measured the power at each port with the power meter for IR beam with the IMC trans power of 1.2W. The configuration can be found in JGW-T1808962-v19. The power is almost consistent with the measurement before with 3W IMC trans power. After we replace the BS with non-polarizing BS from sigma-kk, the reflection is always smaller than transmission. The reflection is around (45±2)%.

[Yuta, Shalika, Kenzaburo, Haoyu]

We measured the noise spectrum of three IR PDs at TMSX.

Gain settings used in the measurement are:

IR PD gain 0 dB, no gain and no filter in the whitening filter.

IR S-pol and P-pol PDs gain: 30 dB, 0 gain in the whitening filter but 3 filter stages are applied.

The current HWP rotation allows most power goes to p-pol.

Fig 1 - Fig 4 show the measurements.

Fig 1: time series data of 3 PDs. Some signal is oscillating in s-pol and p-pol PDs. We think this is caused by the large whitening filter gains.

Fig 2: row spectrum in counts. There are peaks around 60Hz and 120Hz. We think this causes the oscillation.

Fig 3: calibrated spectrum in Volts. The IR PD's spectrum is flat (around 1e-6 V/sqrtHz) above 10Hz, which seems to be the ADC noise.

Fig 4: calibrated spectrum in watts. There is a factor of 2 problem. The real power is roughly 2 times of the value in the plot.

We think 3 filter stages in the whitening filter for s-pol and p-pol PDs are too much. Maybe 1 stage is good.

After this measurement, we turn off all the whitening filters. We need to check this spectrum again in the PRFPMI configuration.

The voltage and power calibrations in Fig 3 and Fig 4 in the last comment were incorrect. The following figures show the correct calibration.

* Fig 1: time series data of 3 PDs showing the DC output. (No change)

* Fig 2: row spectrum in counts. (No change)

* Fig 3: Updated calibration of PDs in voltage.

- Assumption for calibration: the PD output range is ±20V and the ADC is 2^16 bit.

- IR PD setting: no PD gain, no whitening filter gain, 0 filter stage, 0.255 filter bank gain.

- IR S-pol setting: 30 dB PD gain, no whitening filter gain, 3 filter stages, no filter bank gain.

- IR P-pol setting: same as s-pol PD.

(1) IR PD DC output: 4.2 counts / (2^16 counts) * 40 V / 0.255 = 1.0e-2 V

(2) IR S-pol PD DC output: 24 counts / (2^16 counts) * 40 V = 1.5e-2 V

(3) IR P-pol PD DC output: 390 counts / (2^16 counts) * 40 V = 2.4e-1 V

* Fig 4: Updated calibration of PDs in watts.

- PDA100A2 data sheet: Responsivity 0.39 A/W, gain at 0 dB: 1.51e3 V/A, gain at 30 dB: 4.75e4 V/A

(1) IR PD DC power: 1.0e-2 V / (1.51e3 V/A) / (0.39 A/W) = 1.7e-5 W

(2) IR S-pol PD DC power: 1.5e-2 V / (4.75e4 V/A) / (0.39 A/W) = 8.0e-7 W

(3) IR P-pol PD DC power: 2.4e-1 V / (4.75e4 V/A) / (0.39 A/W) = 1.3e-5 W

The rotation of the HWP is put back to 20deg (we forgot to put it back after last measurement).