Resonance and absorption peak of transmission spectrum can be achieved when terahertz pulses transmit
through the split-ring resonators (SRRs). Using the theory of LC oscillating circuit and the model of half wave
resonance, we can account for the phenomenon. We once fabricate metal subwavelength dual-ring structure
which is different from the SRRs and there aren't splits in. The resonance and absorption peak, however, still
appear in the THz frequency range. In this time, we respectively fabricate the dual-ring structure and reverse
dual-ring structure on quartz crystal substrate and silicon. When the metal structure is fabricated on quartz
crystal, Using terahertz time-domain spectroscopy (TDS), we find the characteristic spectra exist as well as time
domain waveform and frequency domain spectra of transmitted terahertz pulses present obviously periodic
variation with rotating the sample round the normal of its surface. However, if silicon is used as substrate, the
phenomena will not appear. In this article, we will analyze the phenomena and obtain the reason resulting in it.
We hold that the metal dual-ring structure in itself can't lead to the variation of the terahertz pulses by changing
the sample's angle due to isotropy of the dual-ring structure in surface of the sample. We think the phenomenon
may originate from quartz crystal substrate.