Fig. 1. Basic principle of electromagnetic induced transparency-like effect. (a) Physical model before EIT-like effect excitation; (b) spectrum before EIT-like effect excitation; (c) physical model after EIT-like effect excitation; (d) spectrum after EIT-like effect excitation

Fig. 2. Schematic diagram of double ring cavity coupling

Fig. 3. Theoretical model of EIT-like effect excited by double ring cavity

Fig. 4. Simulation results of EIT-like effect with double ring cavity excitation. (a) Transmission spectrum of M1; (b) transmission spectrum of M2; (c) FDTD simulation model of double-ring cavity structure; (d) electric-field distribution at λ=1578.66 nm; (e) electric-field distribution at λ=1578.66 nm

Fig. 5. Changes in electric field distribution after varying distance between two cavities. (a) Schematic diagram (from opaque to transparent); (b) changes in electric field distribution at d=0, 0.2, 0.4, 0.6 μm

Fig. 6. EIT-like transmission spectra of double ring cavity structures. (a) Theoretical result at d=0 μm; (b) theoretical resultat d=0.2 μm; (c) theoretical resultat d=0.4 μm; (d) theoretical resultat d=0.6 μm; (e) simulation resultat d=0 μm; (f) simulation resultat d=0.2 μm; (g) simulation resultat d=0.4 μm; (h) simulation resultat d=0.6 μm

Fig. 7. EIT-like transmission spectra corresponding to different gases after varying distance between two cavities. (a) Transmission spectra of different gases at d=0 μm; (b) wavelength shifts and Q variations of different gases at d=0 μm; (c) transmission spectra of different gases at d=0.2 μm; (d) wavelength shifts and Q variations of different gases at d=0.2 μm

Fig. 8. EIT-like transmission spectra after varying distance between two cavities. (a) Transmission spectra of different gases at d=0.4 μm; (b) wavelength shifts and Q variations of different gases at d=0.4 μm; (c) transmission spectra of different gases at d=0.6 μm; (d) wavelength shifts and Q variations of different gases at d=0.6 μm

Fig. 9. Wavelengths for different distances of double-ring cavities