Fig. 1. Schematic of the proposed modulator with perfectly vertical coupling to an SMF. (a) 3D view of the entire structure. (b) Top view of the MZI structure. Cross-sectional 2D view of (c) the modulation section and (d) the coupling interface.

Fig. 2. Simulated results for the proposed modulator. (a) Microwave loss and (b) EO S21 response with varying thickness h_c2 of the SiO₂ layer between the modulator and the UV adhesive. (c) Distributions of the optical and electrical fields at the modulation section. (d) Calculated microwave index, with the red dashed line indicating the optical mode’s group index.

Fig. 3. Fabrication process flow for the proposed modulator: (a)–(d) Steps involved in fabricating the standard TFLN modulator, and (e)–(h) the process of bonding to a quartz substrate using UV adhesive.

Fig. 4. Optical and scanning electron microscope images of the fabricated device. (a) Entire device, (b)–(c) grating coupler, and (d) enlarged view of the modulation region. The output grating coupler is not shown.

Fig. 5. Measured static response of the proposed modulator. (a) Fiber-to-fiber loss, (b) normalized optical transmission during a 100-kHz voltage scan for V_π measurement, and (c) static ER.

Fig. 6. (a) Measured electrical–electrical (EE) response of the proposed modulator. Extracted (b) microwave loss, (c) characteristic impedance, and (d) microwave index from the EE response.

Fig. 7. (a) Measured EO S₂₁ response. (b) BERs for 80 and 100 Gbit/s OOK transmission at different received optical powers. (c)–(d) Eye diagrams for the corresponding modulation signals.

Fig. 8. Schematic configuration of parallel multichannel optical transmitters featuring a perfectly vertical packaged multicore fiber interface based on the proposed modulator.