We investigate extraordinary terahertz transmission through the H-shaped annular aperture arrays (AAAs) drilled in a thin metal film on a doubly polished p-type silicon wafer by use of the traditional terahertz time domain spectroscopy (THz-TDS). A surprising result is that only odd order resonant modes are observed for the symmetrical structures, but both odd and even order resonant modes can be displayed for the asymmetrical structures. Breaking the symmetry of the H-shaped AAAs by gradual displacing the H-shaped AAAs to the U-shaped AAAs allows an intensity modulation depth of 98.7% of the second order resonance. All the resonant frequencies are insensitive to the details of the shape for the H-shaped annular aperture, but mainly depend on the total circumference in a unit cell. Furthermore, a clear inverse proportion relationship between the resonant frequencies and the total circumference is revealed and confirmed experimentally and numerically. The experimental conclusions are verified by the simulation results well. These characteristics pave an avenue to the quick and accurate construction of the desired operating frequencies for filtering, bio-sensing, optical modulation, and ultrafast switching applications.
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Yan Zhang and Dan Hu
Terahertz resonant transmission based on annular aperture arrays
", Proc. SPIE 8759, Eighth International Symposium on Precision Engineering Measurement and Instrumentation, 87593D (January 31, 2013); doi:10.1117/12.2014582; http://dx.doi.org/10.1117/12.2014582