Magnetic Field Control of the Quantum Chaotic Dynamics of Hydrogen Analogues in an Anisotropic Crystal Field

We report magnetic field control of the quantum chaotic dynamics of hydrogen analogues in an anisotropic solid state environment. The chaoticity of the system dynamics was quantified by means of energy level statistics. We analyzed the magnetic field dependence of the statistical distribution of the impurity energy levels and found a smooth transition between the Poisson limit and the Wigner limit, i.e. transition between regular Poisson and fully chaotic Wigner dynamics. Effect of the crystal field anisotropy on the quantum chaotic dynamics, which manifests itself in characteristic transitions between regularity and chaos for different field orientations, was demonstrated.Comment: 4 pages, 4 figure

Direct Observationof DegenerateTwo-Photon Absorption and Its Saturation in WS2 and MoS2 Monolayer and Few-Layer Films

The optical nonlinearity of WS2, MoS2 monolayer and few-layer films was investigated using the Z-scan technique with femtosecond pulses from the visible to the near infrared. The dependence of nonlinear absorption of the WS2 and MoS2 films on layer number and excitation wavelength was studied systematically. WS2 with 1~3 layers exhibits a giant two-photon absorption (TPA) coefficient. Saturation of TPA for WS2 with 1~3 layers and MoS2 with 25~27 layers was observed. The giant nonlinearity of WS2 and MoS2 is attributed to two dimensional confinement, a giant exciton effect and the band edge resonance of TPA

Whispering gallery modes in indium oxide hexagonal microcavities

We report on the use of In₂O₃nanowires with hexagonal cross section as optical whispering gallery resonators. The single-crystal In₂O₃nanowires were fabricated by an in situ thermal oxidation method. Whispering gallery modes(WGMs) in the visible spectral range were directly observed at room temperature. Due to the slight tapering of the nanowires, the energies and orders of the WGMs were modulated when excitations were scanned along the c-axis (length) of the nanowires. The experimental results were explained and fitted well with a plane wave interference model and Cauchy dispersion formula for refractive indices.The work is funded by the NSFC 973 projects and STCSM of China Grant Nos. 2004CB619004 and 2006CB921506. The authors thank the Australian Government Department of Innovation, Industry, Science and Research for funding this collaborative research under the International Science Linkages China Program

Single-crystalline hexagonal ZnO microtube optical resonators

High quality ZnO microtubes with hexagonal cross sections, fabricated via an oxidation-sublimation process, are studied as novel optical resonators. Whispering gallery modes, Fabry-Pérot modes, and an additional set of modes with different polarization