We investigate the line shape of the transmission probability in quantum waveguides with resonantly coupled cavities. Resonance and antiresonance features in the vicinity of each quasibound state can be characterized by a zero-pole pair in the complex-energy plane, which leads to asymmetrical transmission peaks. We have found a generalization of the familiar symmetrical Lorentzian line shape. Using several examples, we demonstrate the utility of our proposed line shape to extract the lifetime of the quasibound state by a fit to the data. We also discuss the asymmetrical line shapes in the context of Fano resonances.

• Received 24 June 1993

DOI:https://doi.org/10.1103/PhysRevB.48.8495