Most tunneling effects are investigated using a one-dimensional model, but such an approach fails to explain the phenomena of the propagation of wave in a system with geometric discontinuities. This work studies the tunneling characteristics in a waveguide system that consists of a middle section with a distinct cutoff frequency, which is controlled by the cross-sectional geometry. Unlike in the one-dimensional case, in which only the fundamental mode is considered, in a virtually three-dimensional system, multiple modes have to be taken into consideration. High-order modes (HOMs) modify the amplitude and the phase of the fundamental mode (TE10), thus subsequently affecting the transmission and group delay of a wave. The effect of the high-order evanescent modes is calculated, and the results are compared with the simulated ones using a full-wave solver. Both oversized and undersized waveguides reveal the necessity of considering the HOMs. The underlying physics is manifested using a multiple-reflection model. This study indicates that the high-order evanescent modes are essential to the explanation of the phenomena in a tunneling system with geometrical discontinuities.
2. Hauge, E. H. and J. A. Stovneng, "Tunneling time: A critical review," Rev. Mod. Phys., Vol. 61, No. 4, 917-936, 1989.
3. Solli, D., R. Y. Chiao, and J. M. Hickmann, "Superluminal effects and negative group delays in electronics, and their applications," Phys. Rev. E, Vol. 66, 056601, 2002.
4. Jackson, A. D., A. Lande, and B. Lautrup, "Apparent superluminal behavior in wave propagation," Phys. Rev. A, Vol. 64, 044101, 2001.
5. Winful, H. G., "Nature of superluminal barrier tunneling," Phys. Rev. Lett., Vol. 90, 023901, 2003.
6. Hartman, T. E., "Tunneling of a wave packet," J. Appl. Phys., Vol. 33, No. 12, 3427-3433, 1962.
7. Winful, H. G., "Delay time and the hartman effect in quantum tunneling," Phys. Rev. Lett., Vol. 91, 260401, 2003.
8. Stenner, M. D., D. J. Gauthier, and M. A. Neifeld, "Fast causal information transmission in a medium with a slow group velocity," Phys. Rev. Lett., Vol. 94, 053902, 2005.
9. Wang, L. J., A. Kuzmich, and A. Dogariu, "Gain-assisted superluminal light propagation," Nature, Vol. 406, 277-279, 2000.
10. Cui, C. L., J. K. Jia, J. W. Gao, Y. Xue, G. Wang, and J. H. Wu, "Ultraslow and superluminal light propagation in a four-level atomic system," Phys. Rev. A, Vol. 76, 033815, 2007.
11. Halvorsen, T. G. and J. M. Leinaas, "Superluminal group velocity in a birefringent crystal," Phys. Rev. A, Vol. 77, 023808, 2008.
12. Steinberg, A. M., P. G. Kwiat, and R. Y. Chiao, "Measurement of the single-photon tunneling time," Phys. Rev. Lett., Vol. 71, No. 5, 708-711, 1993.
13. Von Freymann, G., S. John, S. Wong, V. Kitaev, and G. A. Ozin, "Measurement of group velocity dispersion for finite size three-dimensional photonic crystals in the near-infrared spectral region," Appl. Phys. Lett., Vol. 86, 053108, 2005.
14. Vetter, R. M., A. Haibel, and G. Nimtz, "Negative phase time for scattering at quantum wells: A microwave analogy experiment," Phys. Rev. E, Vol. 63, 046701, 2001.
15. Brodowsky, H. M., W. Heitmann, and G. Nimtz, "Comparison of experimental microwave tunneling data with calculations based on Maxwell's equations," Phys. Lett. A, Vol. 222, 125-129, 1996.
16. Winful, H. G., "Group delay, stored energy, and the tunneling of evanescent electromagnetic waves," Phys. Rev. E, Vol. 68, 016615, 2003.
17. Wang, Z. Y. and C. D. Xiong, "Theoretical evidence for the superluminality of evanescent modes," Phys. Rev. A, Vol. 75, 042105, 2007.
18. Chen, X. and C. Xiong, "Electromagnetic simulation of the evanescent mode," Ann. Phys. (Leipzig), Vol. 7, 631, 1998.
19. Pablo, A., L. Barbero, H. E. Hernandez-Figueroa, and E. Recami, "Propagation speed of evanescent modes," Phys. Rev. E, Vol. 62, No. 6, 8628-8635, 2000.
20. Enders, A. and G. Nimtz, "Photonic-tunneling experiments," Phys. Rev. B, Vol. 47, No. 15, 9605-9609, 1993.
21. Enders, A. and G. Nimtz, "Evanescent-mode propagation and quantum tunneling," Phys. Rev. E, Vol. 48, No. 1, 632-634, 1993.
22. Winful, H. G., "The meaning of group delay in barrier tunnelling: A re-examination of superluminal group velocities," New J. Phys., Vol. 8, 101, 2006.
23. Fleming, J. G., S. Y. Lin, I. El-Kady, R. Biswas, and K. M. Ho, "All-metallic three-dimensional photonic crystals with a large infrared bandgap," Nature, Vol. 417, 52-55, 2002.
24. Capmany, J. and D. Novak, "Microwave photonics combines two worlds," Nature Photonic, Vol. 1, 319-330, 2007.
25. Pozar, D. M., Microwave Engineering, Chap. 5, Addison-Welsey, New York, 1990.
26. Gesell, G. A. and I. R. Ciric, "Recurrence modal analysis for multiple waveguide discontinuities and its application to circular structures," IEEE Trans. Microwave Theory Tech., Vol. 41, No. 3, 484-490, 1993.
27. Rozzi, T. E. and W. F. G. Mecklenbrauker, "Wide-band network modeling of interacting inductive irises and steps," IEEE Trans. Microwave Theory Tech., Vol. 23, No. 2, 235-240, 1975.
28. Davies, P. C. W., "Quantum tunneling time," Am. J. Phys., Vol. 73, No. 1, 23-27, 2004.