Resonant splitting in periodic T-shaped photonic waveguides

Resonant splitting phenomena of photons in periodic T-shaped waveguide structure are investigated by the Green’s function method. An interesting resonant phenomenon is found in the transmission spectra. When the T-shaped structure contains n constrictions, there are (n − 1)-fold resonant splitting peaks in the low frequency region. The peaks are induced by low quasi-bound states in which photons are intensively localized in the stubs, while (n − 2)-fold resonant splitting occurs in the high frequency region. These peaks are induced by the high quasi-bound states where the photons are mainly localized in constrictions rather than in stubs. To this kind of quasi-bound state, the stub acts as a potential barrier rather than a well, which is the inverse of the case of the low quasi-bound states corresponding to the (n − 1)-fold splitting peaks. These resonant peaks can be modulated by adjusting the periodic number and geometry of the waveguide structures. The results can be used to develop optical switching d...