Strong Stimulated Mie Scattering From Plasmonic CuS Nanocrystals in Toluene or Pentane

We report here strong stimulated Mie scattering (SMS) from a grating formed by optically redistributed plasmonic CuS nanocrystals (NCs), which exhibit a strong near-infrared localized surface plasmon resonance. We demonstrate that CuS NCs dispersed in a solvent, such as toluene or pentane, interact strongly with light due to their large polarizability that arises from their high concentration of free charge carriers. The NCs redistribute in the intensity grating that is formed by the interference of forward pump light with backward Mie scattered light. This alignment generates a Bragg grating of CuS NCs, which produces efficient reflection to the plasmonically enhanced backward Mie scattering. We report SMS from CuS NCs suspended in toluene at varying concentrations, pumped by ~816-nm and ~10-ns laser pulses. At the optimum concentration and for a 2-cm cuvette length, the reflectivity (energy transfer efficiency from the input pump to the backward SMS) reached 29%, and the pump energy threshold was 4.8 times lower than that of stimulated Brillouin scattering in pure toluene. The time delay of the backward SMS pulse observed at lower pump energy levels is consistent with reflection from a grating formed by spatial redistribution due to drift mobility of nanoparticles. Changing the solvent from toluene to pentane that has lower viscosity, reduced the delay time, which is also consistent with the nanoparticle redistribution model. The temporal behavior, spectral line shape, and far-field distribution of the backward SMS are presented.