Experimental demonstration of silicon-based topological photonic crystal slab at near infrared frequencies and its dynamic tunability (Conference Presentation)

Abstract

Topological insulators are materials that behave as insulators in their interior but support boundary conducting states due the non-trivial topological order. These edge states are robust to defects and imperfections, allowing lossless energy transport along the surface. Topological insulators were first discovered in field of electronics, but recently photonic analogues of these systems were realized. Most of experimentally demonstrated photonic topological insulators to date are bulky, incompatible with current semiconductor fabrication process or operate in microwave frequency range. In this work, we show silicon photonic-crystal-based Valley-Hall topological insulator operating at telecommunication wavelengths. Light propagation along the trapezoidally-shaped path with four 120 degrees turns is demonstrated and compared with propagation along the straight line. Nearly the same transmittance values for both cases confirm robust light transport in such Valley-Hall topological photonic crystal. In the second part of this talk, we discuss the possibility of dynamic tuning of the proposed topological insulator by modulation of the refractive index of silicon. The modulation is facilitated by shining focused ultraviolet pulsed light onto silicon photonic crystal slab. Ultraviolet light illumination causes formation of electron-hole pairs, excitation of free-carriers and results into decrease of refractive index with estimated modulation on the order of 0.1. Due to the index change, spectral position of the bandgap and the edge states shift allowing their dynamic control. Proposed concept can find applications in communication field for fast all-optical switching and control over light propagation.