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,[1] Pierce on electron beams,[2] and Gould on backward wave oscillators.
[3] This put in place the mathematical foundations for the modern formulation expressed by H. A. Haus et al. for optical waveguides.
[4][5] In the late 1990s and early 2000s, the field of nanophotonics has revitalized interest in coupled mode theory.
[8][9] The oscillatory systems to which coupled mode theory applies are described by second order partial differential equations.