High-sensitivity integrated terahertz sensor with large dynamic range based on adjustable high-<i>Q</i> microring resonator

Terahertz (THz) sensors play an essential role in terahertz sensing, and the whispering gallery mode resonator (WGMR) is one of the competitive platforms to enhance sensitivity. The traditional on-chip WGMRs are challenging with sensing degradation resulting from the deviation in practical fabrication. The adjustable THz sensor based on a silicon Mach–Zehnder interferometer-coupled microring resonator (MZI-MRR) is proposed and designed in this work. With the different heating power, the THz-MZI-MRR can be precisely switched between three coupling states with high repeatability. The maximum extinction ratio and Q are adjusted to 51.2 dB and 1322, respectively. The sensing characteristics of three different states are systematically demonstrated for the first time, exhibiting various unique capabilities. By adjusting the coupling state, the sensor maintains fantastic sensing ability in a larger measurement range. The proposed adjustable THz-MZI-MRR is suitable for complex and practical detection scenarios and should promote the prosperity of THz sensing.