Shortcut to adiabaticity in bent waveguide couplers with a sign flip of the phase mismatch.

Abstract

Bending the axis of a waveguide coupler can result in phase mismatch between the evanescently coupled waveguides. Using a bent waveguide coupler, we realize a shortcut to adiabatic light transfer between waveguides with a sign flip of the phase mismatch. Counterdiabatic driving with unitary transformation cancels non-adiabatic coupling in the waveguide coupler so that light evolution follows the adiabatic modes at short lengths. The counterdiabatic driving protocol is implemented in the waveguide coupler by engineering the waveguide spacing and axis bending profile. The bent waveguide coupler is compact and robust against parameter variations.