Ecofriendly Perovskites with Giant Self-Defocusing Optical Response

摘要

The full optical control of light using sustainable green technologies is oneof the incipient challenges of the Photonics community. There are, however,few optical materials able to provide a significant nonlinear refractive indexchange under small enough intensities (< 1 GW cm~(?2)), and, more importantly,allowing the external control of the magnitude and sign of their nonlinearresponse. This manuscript demonstrates that Cs_2SnI_6 lead-free nanocrystals(NCs) present an extraordinary self-defocusing response not yet observed upto now in any material. Despite its complex structural form, these NCs arefully characterized here, both experimentally and theoretically, revealing agiant negative refractive change Δn = ?0.05 under proper illumination conditions.The nonlinear response is tuned with the intensity, concentration ofNCs in the solvent, and propagation distance leading to a crossover wherethe media transforms to self-focusing with Δn = +0.002. These results canprovide fascinating opportunities in sensing and light–matter interactions fora future ecofriendly photonic technology.