Fig. 1. Schematic diagram of the proposed GADC structure

Fig. 2. Dispersion of the q-TE modes calculated as functions of the waveguide width w at 1 550 nm wavelength for different etching depths of h_e（=150 nm，170 nm，200 nm）

Fig. 3. Transmission spectra of the TMW of the GADC for the E${}_{\mathrm{11}\mathrm{T}}^z$ mode at different period number N of the LPWG

Fig. 4. Simulated propagation dynamics of the designed GADC at 1 550 nm wavelength

Fig. 5. Photograph of the fabricated GADC chip

Fig. 6. Normalized transmission spectra of our typical fabricated GADC when broadband light at fundamental mode was launched into the TMW and the SMW，respectively

Fig. 7. Output near-field patterns taken at the output of the TMW and the SMW of our typical fabricated GADC

Fig. 8. Photograph of the packaged GADC chip

Fig. 9. Normalized transmission spectra of the TMW of our typical fabricated GADC measured at different tuning voltages and variation of the center wavelength with the tuning voltage

Fig. 10. Normalized transmission spectra of the SMW of our typical fabricated GADC measured at different tuning voltages and variation of the center wavelength with the tuning voltage

Fig. 11. Normalized transmission spectra of the TMW of our typical fabricated GADC measured at different temperature and variation of the center wavelength with the ambient temperature