Optimization of adiabaticity in coupled-waveguide devices using shortcuts to adiabaticity

Conventional strategies to design adiabatic coupledwaveguide devices focus on optimizing the system adiabaticity but can only guarantee 100% efficiency at specific lengths. We establish a simple technique allowing the optimization of device adiabaticity and ensuring 100% coupling/conversion efficiency at any physically realizable length. Specifically, we use the shortcuts-to-adiabaticity technique to represent the system state precisely and engineer the system evolution to be as close to the adiabatic state as possible. Smooth parameters are derived for coupledwaveguide devices, which feature good robustness against wavelength and fabrication variations at the same time. The proposed device is verified with beam propagation simulations.