Optically tunable topological photonic crystal

TL;DR

This paper introduces a method for dynamically tuning silicon-based topological photonic crystals using all-optical free-carrier excitation, enabling fast, reversible control of transmission properties at telecommunication wavelengths.

Contribution

It presents a novel approach for optical tunability in topological photonic structures through all-optical free-carrier excitation, which was not previously demonstrated.

Findings

Achieved up to 20 nm blue-shift in transmission spectrum.

Realized approximately 85% reduction in transmission.

Switching times on the order of nanoseconds.

Abstract

Topological photonic insulators pave the way toward efficient integrated photonic devices with minimized scattering losses. Optical properties of the majority of topological structures proposed to date are fixed by design such that no changes to their performance can be made once the device has been fabricated. However, tunability is important for many applications, including modulators, switches, or optical buffers. Therefore, we propose a straightforward way for the dynamic control of transmission in a silicon-based topological photonic crystal enabled by all-optical free-carrier excitation allowing for fast refractive-index modulation. The changes in both real and imaginary parts of refractive index cause up to 20 nm blue-shift of the transmission spectrum and approximately 85% reduction in transmission. With the control mechanism used here, switching times of the order of nanoseconds can be achieved. The structures proposed here are compatible with the standard semiconductor industry fabrication process and operate at telecommunication wavelengths.