Fig. 1. Schematic of refractive index sensor based on MZI. (a) Overall structure; (b) section of strip waveguide; (c) section of slot waveguide

Fig. 2. Electric field distribution in waveguide. (a) TE₀₀ mode of strip waveguide; (b) slot mode of slot waveguide

Fig. 3. Relationship between effective refractive index and wavelength under the same interference length and different waveguide sizes. (a) w_Si=800 nm; (b) w_Si=830 nm; (c) w_Si=860 nm; (d) w_Si=890 nm; (e) w_Si=920 nm; (f) w_Si=950 nm

Fig. 4. Characteristic curves of group refractive index under different w_Si conditions. (a) Intersections of curves under different w_Si and curves with w_strip=1000 nm; (b) relationship between G and wavelength at different w_Si

Fig. 5. MZI spectra characteristic diagram. (a) Transmission spectra of SRI varying from 1.0086 to 1.0066; (b) phase accumulation curves of strip waveguide TE₀₀ mode and slot waveguide slot mode when SRI changes from 1.0086 to 1.0066

Fig. 6. SRI sensitivity analysis diagram. (a) Relationship between refractive index sensitivity and wavelength at different w_Si; (b) wavelength shift curves of A, A', B, B', C, and C' with SRI; (c) distance curves of to AA', BB', and CC' with SRI

Fig. 7. Barometric sensitivity analysis diagram. (a) Transmission spectra of barometric relative pressure varying from 0 to -240 kPa; (b) wavelength shift curves of A, A', B, B ', C, C' with SRI and relative pressure

Fig. 8. Fabrication of on-chip gas chambers using PDMS