Synthesis of Fluorescent Eu-Doped InVO4 Nanocrystals by Using In(OH)3 Templates with Controlled Morphologies.

In this study, In(OH)3 nanocrystals with three morphologies including rods, cubes and spheres were synthesized through a hydrothermal method. The morphology and crystalline were manipulated by controlling the growth speed and the addition of ascorbic acid. The InVO4 nanocrystals were obtained by a process sacrificing In(OH)3 templates. The phase transformation of rods and cubes generated size-controllable products, whereas that of nanospheres formed hollow micro-spheres. InVO4 nanocrystals display a brilliant yellow emission band with the peak at 517 nm. Intriguingly, luminescent rare-earth Eu ions with red emission could be doped into InVO4 nanocrystals during the phase transformation. Excitation and the emission spectra indicated an excitation energy transfer from the vanadate to the rare-earth ions.

Phonon blockade in a nanomechanical resonator quadratically coupled to a two-level system.

We investigate phonon statistics in a nanomechanical resonator (NAMR), which is quadratically coupled to a two-level system, by driving the NAMR and two-level system simultaneously. We find that unconventional phonon blockade (UCPNB), i.e., strong phonon antibunching effect based on quantum interference, can be observed when driven fields are weak. By increasing the strengths of the driving fields, we show the crossover from the UCPNB to the conventional phonon blockade (CPNB), which is induced by the strong nonlinear interaction of the system. Moreover, under the strong coupling condition for CPNB, quantum interference effect can also be used to enhanced the phonon blockade by optimizing the phase difference of the two external driving fields.

Tunable phonon blockade in quadratically coupled optomechanical systems.

We theoretically investigate the phonon statistics of a quadratically coupled optomechanical system, in which an effective second-order nonlinear interaction between an optical mode and a mechanical mode is induced by a strong optical driving field on two-phonon red-sideband resonance. We show that strong phonon antibunching can be observed even if the strength of the effective second-order nonlinear interaction is much weaker than the decay rates of the system, by driving the optical and mechanical modes with weak driving fields respectively. Moreover, the phonon statistics can be dynamically controlled by tuning the strengths and the phase difference of the weak driving fields. The scheme proposed here can be used to realize tunable single-phonon sources with quadratically optomechanical coupling.