Written by Yuta

I calculated the signal amplitudes for Xgreen REFL WFS.
The WFS signal amplitude ratio for SOFT mode and HARD mode is 1:3.8. The Gouy phase separation is 57deg.
Attached figure shows Gouy phase dependence of the WFS signal from both modes. Dots are from Optickle simulation and lines are from analytical calculation.
In my analytical calculation, it assumes high finesse cavity. So, amplitudes are scaled to fit Optickle results in this plot. The ratio of SOFT/HARD or relative Gouy phase does not change. (see Appendix A of T1300497 for more details)

Parameters I used are listed below.

[Parameters]
wavelength: 532 nm
sideband freq: 24.389319 MHz (alog #9708)
modulation depth: 0.1i
input power: 30 mW
power on QPD: 3 mW
cavity length: 3994.4704 m (alog #9626)
ETM RoC: 2241.54 m (alog #9381)
ITM RoC: 1939.52 m
ETM green trans: 38%
ITM green trans: 1%