Transient guided-mode resonance metasurfaces with phase-transition materials

We investigate transient, optically induced metasurface effects in a planar thin-film multilayer based on a phase-transition material. Illumination of a properly designed multilayer with two obliquely-incident and phase-coherent pulsed pumps induces a transient and reversible temperature pattern in the phase-transition layer. The deep periodic modulation of the refractive index, caused by the interfering pumps, produces a transient Fano-like spectral feature associated with a guided-mode resonance. A coupled opto-thermal model is employed to analyze the temporal dynamics of the transient metasurface and to evaluate its speed and modulation capabilities. Using a near-infrared pump pulse with peak intensity on the order of $100\text{ MW/cm}^2$ and duration of a few picoseconds, we find that the characteristic time scale of the transient metasurface is on the order of nanoseconds. Our results indicate that inducing transient metasurface effects in films of phase-transition materials can lead to new opportunities for dynamic control of Q-factor in photonic resonances, and for light modulation and switching.