This is the coupling efficiency v.s. detuning data for: 3 mode coupling of LG00, LG10, and LG20 (some fractions between them)

Coupling efficiency = observed coupling / max efficiency.
-> Max efficiency is obtained from the cavity parameter: cavity loss, reflection, transmission, etc (read the main text).
-> For this expt, max efficiency = (18.23 pm 0.23)%, also taking the cuvette loss into account.

Detuning is defined w.r.t. to the centre of LG_00 modes. 
-> Higher order modes will have a transverse mode spacing (in this expt ~200 MHz), which makes the resonance frequency lower than that of LG_00 modes.