Coupled mode theory

Coupled mode theory (CMT) is a perturbational approach for analyzing the coupling of vibrational systems (mechanical, optical, electrical, etc.) in space or in time. Coupled mode theory allows a wide range of devices and systems to be modeled as one or more coupled resonators. In optics, such systems include laser cavities, photonic crystal slabs, metamaterials, and ring resonators. Coupled mode theory (CMT) is a perturbational approach for analyzing the coupling of vibrational systems (mechanical, optical, electrical, etc.) in space or in time. Coupled mode theory allows a wide range of devices and systems to be modeled as one or more coupled resonators. In optics, such systems include laser cavities, photonic crystal slabs, metamaterials, and ring resonators. Coupled mode theory first arose in the 1950s in the works of Miller on microwave transmission lines, Pierce on electron beams, and Gould on backward wave oscillators. This put in place the mathematical foundations for the modern formulation expressed by H. A. Haus et al. for optical waveguides. In the late 1990s and early 2000s, the field of nanophotonics has revitalized interest in coupled mode theory. Coupled mode theory has been used to account for the Fano resonances in photonic crystal slabs and has also been modified to account for optical resonators with non-orthogonal modes.