Dynamic tuning of anisotropy-induced bound states in the continuum in liquid crystal waveguides

Bound states in the continuum (BICs) are radiationless localized states, embedded within the spectrum of radiative modes, which exhibit unique properties that enable a wide range of phenomena and potential applications. However, in conventional systems—such as photonic crystal structures—the conditions for BIC existence are typically fixed during fabrication, as they depend on the geometry and material parameters of the device. This constitutes an important limitation for tunable or reconfigurable systems. We address this challenge by investigating anisotropy-induced BICs in specially designed waveguides incorporating a liquid crystal (LC) core. We experimentally observe the occurrence of anisotropy-induced interference BICs, a type of BIC whose existence loci in the parameter space depend on the LC optic axis orientation. Then, by applying a voltage across the structure that reorients the LC optic axis, we show the dynamic tuning of different BICs in and out of resonance.