Fig. 2: Device fabrication and resonator characterization.

a Optical microscope image of the fabricated device, comprising a PhC input coupler, a 2.5 mm-long EO modulation section, and a high-reflectivity PhC reflector. b SEM images of the PhC reflector and EO modulation section. The PhC corrugation and the waveguide width are adiabatically engineered to minimize optical losses. c Measured resonant reflectance spectrum (blue). Resonant minima are marked by black dots, and the dark blue line indicates the calculated reflectance of the PhC reflector. d Experimentally extracted Q-factor distributions—intrinsic (purple), coupling (blue), and loaded (dark green). The solid purple line indicates the simulated coupling Q-factor. Inset: Reflection spectrum of a representative resonant mode (blue) with a reference Mach–Zehnder interferometer (MZI) signal (black). e Experimentally extracted integrated dispersion (\({D}_{\mathrm{int}}\)) with respective to the resonant mode at 1550 nm. f Extracted second-order dispersion (\({D}_{2}\)) from the polynomial fitting of \({D}_{\mathrm{int}}\) (solid blue line in (e)) as a function of the mode number \(\mu\). A zero-dispersion point is observed near 1560 nm, which distinguishes anomalous (\({D}_{2} > 0\)) and normal (\({D}_{2} < 0\)) dispersion regimes.