Spatiotemporal Lineshape Tailoring in BIC-Mediated Reconfigurable Metamaterials

The bound state in the continuum (BIC) is a unique nonradiating eigenstate that possesses rich physics and has attracted intensive attention in the field of optics and photonics. Actively tailoring BICs in a designable fashion is highly desired for diversified photonic devices. However, to date, most BIC-assisted works have been limited to showing passive control in a fixed structure configuration without tuning the spectral responses. Here, a new scheme to construct a coupled photon cavity for spatiotemporal lineshape tailoring, in which a nonradiating BIC is embedded in the electromagnetic induced transparency (EIT) window, is proposed. This approach uses the phase transition of VO2 inclusions to induce spatial symmetry breaking, leading to the formation of a quasi-BIC coupled EIT state. As an extra dimension for dynamic tuning, a layer with a transient photoconductivity much shorter than the photon lifetime is introduced to ultrafast switch the leaky modes for both EIT- and quasi-BIC-coupled EIT cavities. As the symmetry-protected BIC and coupling effect are quite common in optical metasurfaces, this proposal provides a general paradigm to active steer spatiotemporal spectrum across multiple dimensions, which is thus believed to promote active metadevices for potential applications in modulators, sensors, filters, and dynamic imaging.