Fig. 1. (a) Schematic of the GeOI MRR for mid-IR range. (b) Magnified images of the ring part. (c) Electric field distribution and neff of the bus waveguide when Wbus was 1.2 μm.

Fig. 2. (a) 3D FDTD simulation for the transmission of the GeOI MRR by varying the G at λ=4.2  μm. (b) Extracted Q factor and ER for the result of (a). (c) Electric field distribution of the GeOI MRR with the indicated dimension in the graph at λ=4.2  μm.

Fig. 3. (a) OM image of the GeOI MRR. (b) SEM image of the GeOI MRR with R of 50 μm. (c) Magnified image of the gap between the bus and ring waveguides.

Fig. 4. (a) Propagation loss measurement of the GeOI waveguides at 4.2 μm λ using the cutback method. (b) Transmission spectrum of the GeOI straight-line waveguide. Inset: simulation of propagation loss with radiation and FCA loss for the GeOI waveguide at a 4.2 μm wavelength. (c) Transmission spectra of the GeOI MRRs with 0.2 μm, 0.5 μm, and 1.0 μm G at 4.18 μm to 4.22 μm λ with 63.5 μm of R for evaluation of the resonant characteristic. (d) Normalized transmission of the MRR (G=0.5  μm) by the transmission of the straight-line waveguide in (b). (e) At 4.2 μm λ, the measurement for high-resolution resonance to estimate the QL of the MRR with an R of 63.5 μm.

Fig. 5. (a) OM image of the racetrack MRR. Inset: magnified image of the coupling region. (b) 3D FDTD simulation for the transmission of the GeOI racetrack MRRs by varying the Lc at λ=4.2  μm. (c) Transmission spectra for the racetrack MRRs at 4.18 μm to 4.22 μm λ. (d) Normalized transmission of the racetrack MRR (Lc=20  μm) by the transmission of the straight-line waveguide. (e) Characterization of QL for the racetrack-type GeOI MRR at 4.2 μm λ.

Fig. 6. QL benchmark for the available mid-IR platform-based MRRs.