The OPO pump relative intensity noise was measured at different power level.
1. MZ offset 4.2 (25 mW), DC voltage on oscilloscope 320mV
2. MZ offset 4.4 (35 mW), DC voltage on oscilloscope 441mV
3. MZ offset 4.0 (15 mW), DC voltage on oscilloscope 186mV
As a reference, in LIGO, the SHG RIN is about 3e-6 from 3Hz to 400Hz. Then it gradually increases to 3e-5 at 4kHz. This indicates that the control servo has 1/f slope. (alog45088)
So we have a better RIN at low frequency (limited by PD dark noise). But a worse RIN at kHz region.
Yuhang, Aritomi, Marc
A new PD (PDA36A-EC) is used (gain is chosen as 0dB), firstly DARK NOISE is measured (saved as DARKL.txt and DARKH.txt)
A LA1608-YAG lens (75mm) was always used when the beam is apparently large.
1. Measure Mephisto RIN. It is measured at the location where we pick off main laser for CC PLL LO.
The DC voltage is measured as 2.66, 2.61V and 2.67V (measured before and after spectra measurements). (saved as MAINL.txt and MAINH.txt)
2. Measure homodyne LO RIN. It is measured just after IRMC transmission.
The DC voltage is measured as 800mV, 780mV (measured before and after spectra measurements). (saved as LOL.txt and LOH.txt)
3. Measure SHG generated GR RIN. It is measured before MZ.
The DC voltage is measured as 3.14V, 3.16V, 3.24V (measured before and after spectra measurements). (saved as SHGL.txt and SHGH.txt)
This is an experiment record. An analysis of data will come later.
A comparison of RIN, shot noise and photo detector dark noise is shown in the attached first figure for several locations on the squeezer bench. Other figures show these noises for different single location separately.