Dispersion engineering in asymmetric dual-width Si3N4 waveguide with high confinement based on super-mode theory

Abstract

Highly dispersive components enable ultrafast optical pulse processing by photonic integrated circuits. This paper presents an asymmetric dual-width silicon nitride (Si3N4) waveguide with high confinement for large dispersion at 1550-nm wavelength. The proposed structure is based on two strip waveguides with different widths. A mode interaction between the two strip waveguide modes is utilized to achieve large dispersion at the desired wavelength. Dispersion engineering of the asymmetric dual-width Si3N4 waveguide based on the super-mode theory overcomes the limitations of traditional dispersion engineering methods. Numerical investigation of the dispersion is performed. Depending on which of the two super-modes is excited in this device, the dispersion is either normal or anomalous, with values of −648 ps/(nm⋅km) and 595 ps/(nm⋅km), respectively. The resonance wavelength of the super-mode can be fine-tuned by varying the width and height of the strip waveguide. The gap between the two strip waveguides is also utilized to tune the value of dispersion. Such a structure should find applications in nonlinear photonic integrated circuits for ultrafast optical pulse processing.