Strong P-band emission and third harmonic generation from ZnO nanorods

We report the room-temperature photoluminescence (PL) and broadband nonlinear optical (NLO) responses from high-quality ZnO nanorods grown by hydrothermal deposition. Based on the PL measurements, we find that the optical quality of ZnO nanorods critically depends on the packing and alignment of the rod structures. Our ZnO nanorods exhibit very strong third harmonic generation with suppressed second harmonic generation when the fundamental wavelength is varied in the range of 1060–2120 nm. Our results imply that ZnO nanostructures can potentially be utilized for various optoelectronic applications involving third-order NLO processes.     

Numerical analysis of waveguide-enhanced optical bistability

We present the results of a simulation study of a multilayer structure for which strongly enhanced (resonant) electric fields are produced at the surface of, and in the interior of, a planar waveguide which is evanescently coupled to an incoming beam in a prism geometry. The resulting field enhancements can far exceed those associated with the well-known surface plasmon resonance in a typical silver film excited in the conventional attenuated total reflection geometry. Simulations are performed for optical bistability for the case of a typical YAG laser beam coupled to a zinc oxide (ZnO) waveguide, demonstrating that the effect should occur for reasonable values of the parameters involved.     

Magnetic field investigation of the acoustic impedance resonance near 2Δ(T) in 3He-A

The acoustic impedance resonance near 2Δ(T) in ³He-A has been studied in magnetic fields up to H = 0.72 T with H?q?. It now appears that the resonance reported by Meisel et al. is independent of ?, q? orientation and satisfies ω(T) = a_ξΔ(T), where Δ(T) is the maximum in the weak coupling axial state gap and a_ξ = 1.8.     

Self-assembled growth of nanostructural Ge islands on bromine-passivated Si(111) surfaces at room temperature

We have deposited relatively thick (∼60 nm) Ge layers on Br-passivated Si(111) substrates by thermal evaporation under high vacuum conditions at room temperature. Ge has grown in a layer-plus-island mode although it is different from the Stranski-Krastanov growth mode observed in epitaxial growth. Both the islands and the layer are nanocrystalline. This appears to be a consequence of reduction of surface free energy of the Si(111) substrate by Br-passivation. The size distribution of the Ge nanoislands has been determined. The Br-Si(111) substrates were prepared by a liquid treatment, which may not produce exactly reproducible surfaces. Nevertheless, some basic features of the nanostructural island growth are reasonably reproducible, while there are variations in the details of the island size distribution.     

Absence of de Haas-van Alphen spin splitting zeros in Au(Fe) at 0.5 K

It is found that the dHvA spin splitting zeros for the neck oscillations in pure Au are absent in a Au (100 ppm Fe) dilute alloy, due to conduction electron - impurity moment exchange interaction. An apparent decrease of the conduction electron scattering rate, with decreasing temperature (down to ～ 0.48 K), is observed for orbits on the belly region of the Fermi surface but not for neck orbits.     

Direct study of the proximity effect in the normal layer inside of the stacked SINIS device

We have observed a striking anisotropy in the electrical transport of layered multiterminal SINIS structures [where S, I, and N denote a superconductor (Nb), an insulator (AlOx), and a normal metal (Al), respectively]. We find that the lateral conductivity of the N layer is dissipative, but a superconducting current can flow normal to the structure, suggesting a direct Josephson coupling between the external S electrodes. A small coherent contribution to the lateral conductivity of the N layer is observed near zero voltage.