Frequency, clockwise to counter clockwise and even to odd lasing mode switching based on optical feedback mechanism

Analyzing modes in a micro-ring waveguide coupled with a feedback resonator reveals that with appropriate parameters, the quality factors of two neighboring ring modes vary periodically and considerably. The effect occurs upon changing the length of the feedback waveguide, whereas the two resonant frequencies remain almost invariant with length change. On the basis of this property, four methods are theoretically demonstrated to realize laser switching: two for frequency switching, one for clockwise to counterclockwise mode switching, and one for even to odd mode switching. The analysis provides methods for bistable lasing and optical logic device design.