Study on the Tunneling Mode in a Sub-Wavelength Open-Cavity Resonator Consisting of Single Negative Materials

We have investigated the process which establishes the tunneling mode in a conjugately matched pair consisting of ε-negative (ENG) and μ-negative (MNG) materials in theory and experiment. The one-dimensional conjugately matched pairs is realized by two L-C loaded transmission lines and the dynamical behavior of the transmitted signal along the pair is measured and recorded on an oscilloscope. It is found that the field does not decay to zero in a finite length single negative material and the average power flow is a constant since the phase difference between electric field and magnetic field varies with the position. While for a conjugately matched ENG/MNG pair, the incident field attenuates in ENG material in the first instance and then the fields are rapidly enhanced at the ENG-MNG interface and reach the steady state due to the resonating effect of the structure. It is revealed that there is a combination of travelling wave and reactive standing wave inside the bilayer with the ratio between them varying with the position. It is also proved that the bilayer can also be treated as an open resonator, in which the charging up characteristic time is in proportion to the Q factor of the structure.