Fig. 1. Schematic diagram of the unit structure of dual-band terahertz sensor. (a) Side view of unit structure; (b) metal microstructure unit of sensor A; (c) metal microstructure unit of sensor B

Fig. 2. Reflection and absorption spectra of the sensors when there is no analyte in the microfluidic channel. (a) Sensor A; (b) sensor B

Fig. 3. Electric field and surface current distribution of the sensors at the resonance frequency. (a),(c) Mode A of sensor A; (b),(d) Mode B of sensor A; (e),(g) Mode A of sensor B; (f),(h) Mode B of sensor B

Fig. 4. Refractive index detection characteristics of the sensors. (a) Sensor A; (b) sensor B

Fig. 5. Electric field distribution in the x-z plane of the sensors at the resonant frequency. (a) Mode A of sensor A; (b) Mode B of sensor A; (c) Mode A of sensor B; (d) Mode B of sensor B

Fig. 6. Absorption spectra of the sensors under TE and TM polarized electromagnetic waves. (a) Sensor A; (b) sensor B

Fig. 7. Absorption and frequency shift change of the sensors with incident angle. (a)--(b) Sensor A; (c)--(d) sensor B

Fig. 8. Absorption change of the sensors with the polarization angle. (a) Sensor A; (b) sensor B

Fig. 9. Influence of manufacturing tolerances on sensing performance of the sensors. (a)--(b) Sensor A; (c)--(d) sensor B