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The propagation of surface water wave pulses over a topographical bottom with randomly arranged cylindrical steps is investigated by multiple scattering theory. It is shown that the waves within a certain frequency range can be localized due to the strong multiple scattering process. In the localized state, the wave intensity decreases exponentially as the transmitted distance increases. By making use of this effect, some components contained in the pulse can be filtered or inhibited by the cylinder ensemble and trapped for a relatively long period of time until dissipation. [ABSTRACT FROM AUTHOR]

We show some properties of the acoustic propagation in two-dimensional sonic crystals, formed by parallel rigid cylinders placed in air. The transmission through slabs of sonic crystals and the associated band structures are considered. It is shown that within partial band gaps, the waves tend to be collimated or guided into the direction in which the propagation is allowed. Such a feature also prevails in the situations in which deaf bands appear. We show that within the partial band gaps, a stable imaging effect can be obtained for flat sonic crystal slabs, in analogy to the cases with photonic crystals. [ABSTRACT FROM AUTHOR]

We synthesis uniform Au-CdS core-shell hetero-nanorods and demonstrate the effective plasmon-exciton interaction induced optical nonlinear enhancement in metal-semiconductor hetero-nanostructures. After growing CdS semiconductor shell onto the Au nanorods, the longitudinal plasmon resonance exhibits considerable red-shift with enlarged absorption intensity. Nonlinear absorption responses transform from saturable absorption to reverse saturable absorption, and effective nonlinear absorption coefficient β is increased from -7.7 to +22.2 cm/GW. The observed behaviors indicate strong plasmon-exciton interaction and great local field enhancement. [ABSTRACT FROM AUTHOR]

The localization caused by multiple scattering of lightwaves provides a mode for random laser action. It is shown that once the gain surpasses a certain threshold, photons are driven to localized modes, which greatly suppresses the energy loss and leads to laser emission. Concurrent with the localization of the random laser, unique collective behaviors of the localized modes appear, as distinguished from the other modes, which reveals the “invisible” microcavities of random lasers. [ABSTRACT FROM AUTHOR]

We report a hollow type piezoelectric micromotor made of a PZT ceramic/metal composite cylinder with sizes of only 3.6 mm in diameter and 3.0 mm in length aiming at medical endoscope application. The hollow piezoelectric stator of the micromotor, acting as a nut, can excite E02-mode traveling wave along its circumferential direction, and a hollow rotor with a fine lens inside, acting as a screw, is driven to produce a spiral motion along its axis direction inside the hollow stator via the traveling wave. The features of the developed micromotors are its hollow, fine structure and submicrometer step resolution, ensuring that the optical path passes in a narrow and limited space and that the optical focal length is tuned precisely inside the endoscope, which is meaningful in medical diagnosis. [ABSTRACT FROM AUTHOR]

In this experiment, a flip-chip light-emitting diode with photonic crystal was fabricated at the interface of p-GaN and Ag reflector via nanospheres lithography technique. In this structure, photonic crystal could couple with the guide-light efficiently by reason of the little distance between photonic crystal and active region. The light output power of light emitting diode with embedded photonic crystal was 1.42 times larger than that of planar flip-chip light-emitting diode. Moreover, the embedded photonic crystal structure makes the far-field divergence angle decreased by 18° without spectra shift. The three-dimensional finite difference time domain simulation results show that photonic crystal could improve the light extraction, and enhance the light absorption caused by Ag reflector simultaneously, because of the roughed surface. The depth of photonic crystal is the key parameter affecting the light extraction and absorption. Light extraction efficiency increases with the depth photonic crystal structure rapidly, and reaches the maximum at the depth 80 nm, beyond which light extraction decrease drastically. [ABSTRACT FROM AUTHOR]