Fig. 1. Schematic of the WGMR for sensing. (a) The structure diagram of the WGMR includes a straight waveguide and a resonator. The inset depicts the cross section of the ridge waveguide. (b) Simulated transmission spectrum of the WGMR for lactose sensing. (c) Simulated transmission spectrum of the WGMR when unloaded. (d) Single-pass coefficient of the WGMR when covered by 1 mm lactose. (e) Normalized electric field distribution of the ridge waveguide. (f) Transmissivity of the WGMR and straight waveguide for different amounts of lactose at 532 GHz.

Fig. 2. Experimental setup diagram. (a) In the experimental setup, THz waves are emitted from the emitter, focused by the lenses and horn antenna to fulfill the coupling into the WGMR, and finally received by the receiver. (b) Photography of the chip. (c) Intensity and phase transmission spectra of the THz-WGMR. The black circles and red curves are experimental and simulated results, respectively.

Fig. 3. Experimental results of the WGMR. (a) Transmission spectra of the WGMR for different amounts of lactose. (b) Transmission spectra of the WGMR for different amounts of glucose. (c) Transmissivity of the mode 1 at 532 GHz and mode 2 at 534 GHz for different lengths of lactose. (d) Transmissivity for different lengths of glucose.

Fig. 4. Experimental results by the straight waveguide. (a) Transmission spectra of the straight waveguide for different amounts of lactose. (b) Transmission spectra of the straight waveguide for different amounts of glucose. (c) Transmissivity at 532 GHz for different lengths of lactose. (d) Transmissivity at 532 GHz for different lengths of glucose.