Nonreciprocal transmission in a photonic-crystal Fano structure enabled by symmetry breaking

TL;DR

This paper presents a compact photonic-crystal device that achieves efficient, low-power nonreciprocal light transmission using Fano resonance and symmetry breaking, suitable for high-speed photonic circuits.

Contribution

It introduces a novel photonic-crystal structure combining Fano resonance and symmetry breaking for nonreciprocal transmission at ultra-low power levels.

Findings

Demonstrated nonreciprocal operation at 10 Gbit/s

Achieved low energy consumption of 4.5 fJ/bit

Utilized ultrafast carrier dynamics for nonlinearity

Abstract

Nanostructures that feature nonreciprocal light transmission are highly desirable building blocks for realizing photonic integrated circuits. Here, a simple and ultra-compact photonic-crystal structure, where a waveguide is coupled to a single nanocavity, is proposed and experimentally demonstrated, showing very efficient optical diode functionality. The key novelty of the structure is the use of a Fano resonance in combination with spatial symmetry breaking and cavity enhanced material nonlinearities to realize non-reciprocal propagation effects at ultra-low power and with a good wavelength tunability. The nonlinearity of the device relies on ultrafast carrier dynamics, rather than the thermal effects usually considered, allowing the demonstration of nonreciprocal operation at a bit-rate of 10 Gbit/s with a low energy consumption of 4.5 fJ/bit.