I vaguely remember that the ALS count (Phase Tracker output) is converted to Hz@532nm by a factor ~20kHz/cnt.
This means the calibration for the IR frequency is 10kHz/cnt.
If this is true 100cnt is 2MHz. Isn't it too big?
Assuming 38.5m for the arm length, FSR is 3.89MHz. (~389cnt)
Our sideband is at integer multiples of 11.03MHz. So...
1xf1 is 0.62MHz (62cnt) away from the carrier
2xf1 is 1.24MHz (124cnt)
3xf1 is 1.86MHz (186cnt)
5xf1=1xf2 is 0.79MHz (79cnt)
10xf1 = 2xf2 is 1.58MHz (158cnt)
15xf1 = 3xf2 is 1.52MHz (152cnt)
So we have to be well with in 62cnt to avoid resonating modulation sidebands.
There maybe some mistake in the factors.
e.g. Phase Tracker calibration is not correct, or CARM ALS OFFSET has factor 2 different calibration from the arm ALS offset. |