Retime-mapping terahertz vernier biosensor for boosting sensitivity based on self-reference waveguide interferometers

The optical vernier effect serves as a potent mechanism for boosting sensitivity and accuracy in the communication band, which is a prominent hotspot in coherent detection. Extending vernier gain to the terahertz window exhibits significant appeal in next-generation wireless communication and high-resolution sensing. Here, a terahertz vernier biosensor is constructed utilizing two overlapping Mach-Zehnder interferometers within a three-channel metallic waveguide. The self-reference feature of the vernier biosensor facilitates a sensitive envelope, and the vernier gain significantly amplifies the detection sensitivity and accuracy from the superposition of slightly detuned terahertz interference spectra mapping within the time-frequency-time domain. An exalting sensitivity of 22.54 THz/RIU is demonstrated at operating frequencies near 0.9 THz and experimentally shows immense sensing performance in detection sensitivity and accuracy of biochemical sample areic mass are 10⁷ GHz/(g/mm²) and 10^-8 g/mm², respectively, presenting an enhancement of > 3000% compared to a single interferometer. Moreover, the sensor is employed to assess the amino acid oxidation characteristic curve analysis in the terahertz range, which assists in identifying specific amino acids. The validation of the vernier effect operating in the terahertz regime demonstrates the development of a rapid and label-free assistance tool for the identification of biochemical samples.