Fig. 4: Device characterizations.

a Experimental setup using a Vector Network Analyzer (VNA) to drive ferroelectric nematic liquid crystals (FN-LC) Mach-Zehnder Modulator (MZM) in push-pull configuration. A DC voltage (V_DC) is used to bias the MZM at its quadrature point and perform the alignment step (i.e., Fig. 3a, b) (see Methods). b MZM schematic showing two 500 μm-long electro-optic phase shifters (EOPS) and mode converters equipped with grating coupler and photonic wire bond optical I/O channels. The alignment has been performed unipolarly, as evidenced by the green arrows (i.e., S is grounded, while V_align and  −V_align applied to G₁ and G₂ electrodes, respectively.) This configuration ensures that the FN-LC is aligned in the same direction in both arms. During RF operation, the signal is applied bipolarly to achieve push-pull performance, as the blue arrows show (i.e., it excites S, with G₁ and G₂ grounded). The proposed EOPS incorporates both slow and fast phase shift mechanisms compared to the conventional approach, shown in c, in which a power-inefficient and slow effect (e.g., thermo-optic) biased by V_b is required in conjunction with a fast EOPS for advanced modulation schemes. d The measured ∣S₂₁∣ values of the undoped finger-loaded strip (FLS) device and the simulations of a doped FLS superimposed over those of a doped slot waveguide (data obtained from ref. ⁵⁷ with permission under Creative Commons license CC BY 4.0). The V_πL values derived from the ∣S₂₁∣ data as a function of frequency are also displayed. e The power spectral density of a double-sideband modulated optical signal (at a carrier frequency f_c) utilizing a sinusoidal signal (at f_m) to drive the MZM. Optical amplitude difference of the carrier-1st and 1st-2nd harmonics, denoted by Δy₁ and Δy₂ can be used to estimate V_π (Supplementary Note 4).