Shortcut to adiabatic light transfer in waveguide couplers with a sign flip in the phase mismatch

TL;DR

This paper introduces a shortcut to adiabaticity method for designing shorter, robust, and achromatic waveguide couplers with a phase mismatch sign flip, enabling efficient optical switching and beam splitting.

Contribution

It presents a novel design for waveguide couplers using counterdiabatic shortcut to adiabaticity, reducing device length and enhancing robustness without increasing coupling strength.

Findings

Achromatic optical switch for two waveguides

Equal superposition beam splitter for three waveguides

Operation robustness against parameter variations

Abstract

Employing counterdiabatic shortcut to adiabaticity (STA), we design shorter and robust achromatic two- and three- waveguide couplers. We assume that the phase mismatch between the waveguides has a sign flip at maximum coupling, while the coupling between the waveguides has a smooth spatial shape. We show that the presented coupler operates as a complete achromatic optical switch for two coupled waveguides and as an equal superposition beam splitter for three coupled waveguides. An important feature of our devices is that they do not require larger coupling strength as compared to previous designs, which make them easier to realize in an experimental setting. Additionally, we show that the presented waveguide couplers operate at a shorter device length and are robust against variations in the coupling strength and the phase mismatch.