Resonant splitting in periodic T-shape photonic waveguides

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Resonant splitting phenomena of photons in periodic T-shape waveguide structure are investigated by the Green's function method. It is found that, except for the (n-1)-fold resonant splitting in the low frequency region, (n-2)-fold resonant splitting occurs in the high frequency region of the transmission spectra. The (n-2)-fold resonant splitting peaks are induced by the high quasi-bound states where the photons are mainly localized in the constrictions rather than in the 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.