Active coupling control in densely packed subwavelength waveguides via dark mode

TL;DR

This paper presents a novel active coupling control method in densely packed subwavelength waveguides using dark mode and adiabatic elimination, enabling efficient, lossless manipulation for integrated photonics applications.

Contribution

It introduces a unique scheme based on dark mode and adiabatic elimination for active, lossless coupling control in densely packed waveguides, advancing integrated photonics technology.

Findings

Successful experimental demonstration of active coupling control

Tuning mode index via dark mode leaves signal unaffected

Potential for ultra-dense integrated nano-photonics applications

Abstract

The ever growing need for energy-efficient and fast communications is driving the development of highly integrated photonic circuits where controlling light at the nanoscale becomes the most critical aspect of information transfer . Directional couplers, two interacting optical waveguides placed in close proximity, are important building blocks in these integrated photonics circuits and have been employed as optical modulators and switches for high speed communication, data processing and integrated quantum operations. However, active control over the coupling between closely packed waveguides is highly desirable and yet remains a critical barrier towards ultra small footprint devices. A general approach to achieve active control in waveguide systems is to exploit optical nonlinearities enabled by a strong control pulse. However these devices suffer from the nonlinear absorption induced by the intense control pulse as the signal and its control propagate in the same waveguide. Here we experimentally demonstrate a unique scheme based on adiabatic elimination (AE) concept that effectively manipulates the coupling between densely packed waveguides. We demonstrate active coupling control between two closely packed waveguides by tuning the mode index of an in-between decoupled waveguide. This is achieved via a dark mode and thus leaves the signal unaffected by the induced losses. Such a scheme is a promising candidate for ultra-dense integrated nano-photonics such as on-chip ultrafast modulators and tunable filters for optical communication and quantum computing.