Light confinement and supercontinuum generation switching in photonic-molecule modes of a microstructure fiber

The modes guided in a ring system of microstructure-integrated fibers are shown to have much in common with electron wave functions in a two-dimensional polyatomic cyclic molecule. This photonic-molecule analogy provides, in particular, an illustrative and physically clear model of dispersion properties and the mode structure of an electromagnetic field in microstructure fibers of the considered type. A high degree of light confinement in waveguide modes of such a photonic molecule enhances nonlinear-optical processes, permitting an octave spectral broadening to be achieved for low-energy femtosecond laser pulses.