Topological edge state assisted dynamically tunable microwave propagations in photonic crystals

Abstract

Topological photonics has emerged as a cutting-edge and intriguing field that permits electromagnetic waves to transmit with minimal losses even when they come in contact with sharp turns or imperfections or defects. In this study, we validate a strategy to realize dynamically amplitude tunable light propagation in a topological waveguide based on a three-dimensional printed valley Hall photonic crystal structure operating in the microwave frequency region. Here, tunable light propagation is facilitated by inserting an active defect in the form of a semiconductor (silicon) material slab across the domain boundary of the topological waveguide. In this configuration, dynamic variation of transmission amplitude is realized via photoexcitation of the semiconductor defect using an external laser of wavelength, $\lambda \,\sim \,510{ }$ nm. This results in active amplitude tunability of $ \sim \, - 10{ }$ dB in topological wave propagation under a photoexcitation of 100 mW. Our demonstrated route can lead to the design of dynamically controlled topological photonic devices such as optical modulators, switches, optical buffers, etc which are important for the development of 6G communication systems.

Keywords

• topological insulators
• dynamically tunable
• electromagnetic waves
• photonic crystals