Study on split-ring-resonator based terahertz sensor and its application to the identification of product oil

Based on the finite-integration-technology method, we calculate the high and low frequency resonant peaks of the split-ring-resonators (SRRs) which served as a terahertz sensor. An equivalent three-SRRs model is introduced to understand the SRR structure at the high frequency resonant absorption peak. At the same time, an equivalent circuit is set up to calculate the high frequency resonant peak. After that, we theoretically study the sensitivity of these two peaks. The results suggest that both of these two resonant peaks show redshift when the permittivity of surrounding medium increase, and the high frequency peak is more sensitive to this permittivity variation than the low one. The SRR sample is fabricated using a surface micromachining process and used to identify gasoline of 93# and 97#. The experiment results show that the redshift of the high frequency resonant peak is larger than that of the low one, and it is in good agreement with theory analysis. This study suggests that the SRR is a good sensor to identify the product oil, and its high frequency resonant peak is more sensitive to the variation of the permittivity than the low one.