Optical fabrication and arrangement control of nanoparticles in superfluid helium

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We successfully fabricated single-crystalline semiconductor microspheres that have surfaces with atomic-level smoothness. These microspheres were formed by performing laser ablation in superfluid helium to create and moderately cool a melt of the anisotropic semiconductor material. This novel method provides cooling conditions that are exceptionally suited for the fabrication of single-crystalline microspheres.We also successfully demonstrated optical manipulation of semiconductor nanoparticles, CuCl, ZnO, and CdSe in superfluid helium that shows low temperature, negligibly small viscosity, and high thermal conductivity. In the manipulation process we can simultaneously sort the size of the particles, because the radiation force is strongly dependent on the resonant condition of the confined excitons in the particles, which is determined by the size. In other words, we succeeded in the selection of the energy levels of the semiconductor nanoparticles.