Ultrabroadband and Flattened Dispersion in Aluminum Nitride Slot Waveguides

Aluminum nitride (AlN) is an emerging platform for a wide range of on-chip applications. One promising feature is that both the second- and third-order nonlinearities are available in crystalline AlN waveguides. We design an AlN slot waveguide with a flat and low dispersion over an ultrawide spectral range from near-infrared to mid-infrared. A dual-slot structure is designed and the flattened group velocity dispersion within -13 and +11 ps/(nm·km) over 2000-nm-wide bandwidth with three zero dispersion wavelengths is achieved. The impacts of the structural parameters are analyzed in detail and the phase-matching condition in four-wave mixing process is investigated as well. A 3-dB conversion bandwidth of 1200 nm and -28-dB conversion efficiency are predicted in a 1-cm-long horizontal dual-slot AlN waveguide with the pump power of 2 W.