Fig. 1. (a) Simulation of waveguide cross-section with the fundamental TE0 mode. (b) Optical micrograph of the fabricated AlScN micro-ring modulator. (c) SEM image of the AlScN waveguide cross-section. (d) Measured transmission spectra of spiral waveguides of different lengths. The optical transmission is normalized to 0-dBm launched optical power and additional losses in the measurement optical link. (e) Waveguide total insertion loss versus waveguide length. The slope of the linear fit indicates the waveguide propagation loss in dB/cm at 1550 nm.

Fig. 2. Measured transmission spectrum of (a) an add-drop and (c) an all-pass MRR. (b), (d) Normalized resonance profiles fitted according to the Lorentzian function to extract Q values. The blue dots represent the measured values and the red line is the fitted curve. (e) Measured resonance shift under different applied voltages. (f) DC characterization of the EO micro-ring modulator. The red squares correspond to the resonance peak shifts at applied voltages of 0 V, 10 V, 20 V, and 30 V. The blue line represents the linear fit to the experimental data. A highly linear relationship between the resonance shift and the applied voltage is observed.

Fig. 3. (a) Schematic of the measurement setup characterizing the high-frequency EO response. Optical transmission spectra of (b) device A and (c) device B are measured at different RF frequencies. The measurements at 12 GHz are used to extract the effective in-device EO coefficient.

Fig. 4. (a) Measured half-wave voltage-length products at high frequencies. (b) Optical sideband power of device A versus various modulation frequencies and applied voltages. All measurement results are averages of multiple measurements, with error bars included.

Fig. 5. Fabrication process of the AlScN micro-ring modulator.

Fig. 6. (a) Cross-sectional view of the numerically calculated electric field distribution. The dominating effective electric field contributing to modulation is the out-of-plane component Ez. (b) Numerically calculated effective electric field within the waveguide and optical absorption as functions of deposited oxide cladding thickness (tox).

Fig. 7. Relationship between the EO coefficient of AlScN and Sc concentration predicted by first-principles calculations.

Fig. 8. (a) Calculated and measured EO response of the AlScN micro-ring modulator for different Vpp. (b) Calculated EO response of the AlScN micro-ring modulator for different detuning wavelengths.