Distortionless pulse transmission in valley photonic crystal slab waveguide

TL;DR

This paper demonstrates distortionless pulse transmission in a valley photonic crystal waveguide with sharp bends, using robust edge states to achieve high-fidelity optical signal transmission in microwave regimes.

Contribution

The study experimentally shows distortionless pulse transmission in a sharply bended valley photonic crystal waveguide, confirming the robustness of edge states for optical signal integrity.

Findings

Gaussian pulse transmitted without distortion

Full width at half maximum changed slightly

Confined edge states confirmed without out-of-plane radiation

Abstract

Valley photonic crystal is one type of photonic topological insulator, whose realization only needs P-symmetry breaking. The domain wall between two valley-contrasting photonic crystals support robust edge states which can wrap around sharp corners without backscattering. Using the robust edge states, one can achieve the pulse transmission. Here, using time-domain measurement in the microwave regime, we show distortionless pulse transmission in a sharply bended waveguide. An Omega-shaped waveguide with four 120-degree bends is constructed with the domain wall between two valley photonic crystal slabs. Experimental results show the progress of Gaussian pulse transmission without distortion, and the full width at half maximum of the output signal was changed slightly in the Omega-shaped waveguide. By measuring steady state electric field distribution, we also confirmed the confined edge states without out-of-plane radiation which benefits from the dispersion below the light line. Our work provides a way for high-fidelity optical pulse signal transmission and develop high-performance optical elements such as photonic circuits or optical delay lines.