Patent ID: 7701983

Claim:
A tuning method for controlling a resonant wavelength of a multiple resonator, the method comprising: providing a multiple resonator comprising three or more resonant elements connected in series, wherein a first resonant element has a shorter optical path length than the other resonant elements, and wherein the remaining resonant elements other than the first resonant element have a tunable device associated therewith; and simultaneously changing respective optical path lengths of each of the three or more resonant elements using the tunable devices, such that the multiple resonator resonates at a wavelength where frequencies of the three or more resonant elements with shifted cycles intersect, wherein the optical path lengths of the resonant elements are L 0 , L 1 , L 2 and M 1 >1 and M 2 >1, the optical path lengths are defined as L 1 = M 1 M 1 - 1 ⁢ ⁢ L 0 , ⁢ L 2 = M 2 M 2 - 1 ⁢ ⁢ L 0 , phase amount “P M ” is the changed optical path length standardized by one-wavelength of the optical path length, and the respective phase amount “P M ” of the plurality of resonant elements whose optical path lengths are to be changed are defined as “P M1 ” and “P M2 ”, and the tunable device controls the increase/decrease amount of the phase amount “P M1 ” and “P M2 ” based on a function with a slope of M 2 - 1 M 1 - 1 .