Optically Reconfigurable Spherical Ge‐Sb‐Te Nanoparticles with Reversible Switching

Tunable and ultracompact optical elements are highly important for the development of advanced nanophotonics. Such elements significantly expand the capabilities of photonic circuits and devices. Phase changing materials based on Ge‐Sb‐Te composition are very promising for tunable nanophotonic elements. This family of materials is excellent for the creation of tunable optical elements, since it has a non‐volatile reversible phase transition and exhibits a strong modulation of the dielectric permittivity in broad spectral range. In this work, fabrication of Ge‐Sb‐Te nanoparticles by laser ablation as well as strong and repeatable changing of their optical properties by fs‐laser irradiation are demonstrated. Beside the control of linear optical response, switchable second harmonic generation from Ge‐Sb‐Te nanoparticles over two orders of magnitude after the phase change is also demonstrated.