Transient guided-mode resonance metasurfaces with phase-transition materials

We investigate transient, photo-thermally induced meta -surface 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 spec-tral 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 near -infrared pump pulses with peak intensities of the order of 100 MW/cm2 and duration of a few picoseconds, we find that the characteristic time scale of the transient metasurface is of the order of nanoseconds. Our results indicate that induc-ing transient metasurface effects in films of phase-transition materials can lead to new opportunities for dynamic control of quality (Q)-factor in photonic resonances, and for light modulation and switching. (c) 2023 Optica Publishing Group