Fig. 1. Proposed TFLN EO modulator with backside holes on a silicon substrate using the CLTW electrode. (a) Three-dimensional views of the whole device and the cross-section at the modulation section. (b) Cross-sectional view of the misaligned device, showing all its structural parameters.

Fig. 2. (a) Simulated RF mode profile at the microwave frequency of 100 GHz. (b) Simulated TE optical mode profile and static electrical field distribution. V_πL = 2.10 V·cm can be extracted. Simulated frequency-dependent results of (c) microwave loss α_m, (d) microwave effective index n_m, and (e) characteristic impedance Z_c. The red dashed line in (d) corresponds to the optical group index n_g.

Fig. 3. (a) Effects of the width r of backside holes on Z_c and n_m at 100 GHz. The optimal points (r = 55 µm) adopted in the experiments are marked as yellow stars. The blue triangles are n_m extracted from experiments. (b) Effects of the misalignment s of backside holes on Z_c and n_m when r = 55 µm.

Fig. 4. (a) Top view of partial electrode. Backside view of the device focusing on (b) the electrode and (c) surface of chip backside. (d) Image of the whole fabricated device.

Fig. 5. Normalized optical transmission of the fabricated MZM as a function of the applied voltage. The V_π value is also marked. The inset shows the measured transmissions in a logarithmic scale showing the insertion loss and extinction ratio of the device.

Fig. 6. (a) Measured EE reflection S₁₁ and transmission S₁₂. (b) Measured and simulated EO transmission S₂₁. Extracted (c) microwave loss α_m and (d) microwave effective index n_m.

Fig. 7. High-speed data transmissions using the fabricated EO MZM. Measured optical eye diagrams for the OOK format at data rates of (a) 80 Gb/s and (b) 100 Gb/s. Measured optical eye diagrams for the PAM-4 format at data rates of (c) 40 Gbaud (80 Gb/s) and (d) 56 Gbaud (112 Gb/s).