ISS loop was not closed by below factors.

1, Actuator of ISS( AOM ) alignment was not good.

2, ISS servo gain was inappropriate.

We made a change these and remeasured open loop gain(below figure) (UGF=63kHz).

 

Next, we measured RIN(below figure) with ISS in-loop PD and ISS out-of-loop PD.

Yellow line is Free run, red line is in-loop, blue line is out-of-loop.

It seems that RIN of in-loop and out-of-loop limited by something noise around 10^-7/rHz.

At this time, main laser power was 3.1 W ,input power of in-loop PD was 3.45 mW and out-of-loop PD was 3.17 mW and koach filter was off.

 

The result of noise budget is this figure. We can not measure the servo noise,so it is not contain elec noise.

   In-loop     : High frequency side is limited by laser noise, low frequency may be limited by elec noise(when servo noise is measured,it will be made clear.).

Out-of-loop : High frequency side is limited by laser noise and low frequency side is limited by elec noise.