We show that short-pulse laser-induced classical ripples on dielectrics, semiconductors, and conductors exhibit a prominent "non-classical" characteristic-in normal incidence the periods are definitely smaller than laser wavelengths, which indicates that the simplified scattering model should be revised. Taking into account the surface plasmons (SPs), we consider that the ripples result from the initial direct SP-laser interference and the subsequent grating-assisted SP-laser coupling. With the model, the period-decreasing phenomenon originates in the admixture of the field-distribution effect and the grating-coupling effect. Further, we propose an approach for obtaining the dielectric constant, electron density, and electron collision time of the high-excited surface. With the derived parameters, the numerical simulations are in good agreement with the experimental results. On the other hand, our results confirm that the surface irradiated by short-pulse laser with damage-threshold fluence should behave metallic, no matter for metal, semiconductor, or dielectric, and the short-pulse laser-induced subwavelength structures should be ascribed to a phenomenon of nano-optics.

Utilizing the coupled piezoelectric and semiconducting dual properties of ZnO, we demonstrate a piezoelectric field effect transistor (PE-FET) that is composed of a ZnO nanowire (NW) (or nanobelt) bridging across two Ohmic contacts, in which the source to drain current is controlled by the bending of the NW. A possible mechanism for the PE-FET is suggested to be associated with the carrier trapping effect and the creation of a charge depletion zone under elastic deformatioin. This PE-FET has been applied as a force/pressure sensor for measuring forces in the nanonewton range and even smaller with the use of smaller NWs. An almost linear relationship between the bending force and the conductance was found at small bending regions, demonstrating the principle of nanowire-based nanoforce and nanopressure sensors.

Fabrication of nanoscale biosensors based on nanowires (NWs), [1][2][3][4][5] nanotubes (NTs), [6][7][8][9] and other nanomaterials [10] has recently attracted enormous attention. In comparison to nanoparticles, 1D NWs and NTs have higher sensitivity because of depletion or accumulation of charge carriers at the surface that is caused by binding of charged biological macromolecules at the surface, and affects the entire cross-sectional conduction pathway.[4] Among all 1D nanomaterials, Si NWs and carbon NTs are the most studied materials as biosensors.Functionalized Si NWs and carbon NTs have been demonstrated for detecting proteins, [2] DNA and DNA sequence variations, [4] and cancer markers. [3] However, the biocompatibility and biodegradability of these nanostructures remain to be studied. For example, carbon NTs injected into human blood vessels might accumulate and occlude capillaries in the human brain, which could cause serious damage or be fatal. Being a key functional material with versatile properties, such as dual semiconducting and piezoelectric properties, ZnO has important applications in optoelectronic devices, sensors, lasers, transducers, and photovoltaic devices. [11][12][13] In addition, the morphology [12,[14][15][16][17][18] and the dopant concentration [19] of ZnO nanostructures can be well controlled by tuning the growth conditions, which further broadens their applications. ZnO nanoparticles are believed to be nontoxic, biosafe, and possibly biocompatible, and have been used in many applications in our daily life, such as drug carriers and cosmetics. However, no literature is available on the biodegradability and biocompatibility of ZnO nanowires or nanobelts, which is crucial for the application of ZnO nanostructure for biosensing.In this paper, we present the first study on biodegradability and biocompatibility of ZnO wires. We have conducted a systematic study on the etching and dissolving behavior of ZnO NWs in various solutions with moderate pH values, including deionized water, ammonia, NaOH solution, and horse blood serum. The result shows that ZnO can be dissolved by deionized water (pH ≈ 4.5-5.0), ammonia (pH ≈ 7.0-7.1, 8.7-9.0) and NaOH solution (pH ≈ 7.0-7.1, 8.7-9.0). The study of the interaction of ZnO wires with horse blood serum shows that the ZnO wires can survive in the fluid for a few hours before they eventually degrade into mineral ions. The results of this study are of great significance. First, biosensors made of ZnO nonmaterial have a certain time to perform a device function. Secondly, once completing the corresponding service, the ZnO wires can eventually dissolve into ions that can be completely absorbed by the body and become part of the nutrition. The biodegradability and biocompatibility of ZnO NWs would allow their use for in vivo biosensing and biodetection.Synthesized by a vapor-solid growth process, [12] the ZnO wires used in our study grew along the [0001] direction with a hexagonal cross section and were of high crystalline quality. We studied the dissolv...

Hyperbolic media have attracted much attention in the photonics community due to their ability to confine light to arbitrarily small volumes and their potential applications to super-resolution technologies. The two-dimensional counterparts of these media can be achieved with hyperbolic metasurfaces that support in-plane hyperbolic guided modes upon nanopatterning, which, however, poses notable fabrication challenges and limits the achievable confinement. We show that thin flakes of a van der Waals crystal, α-MoO3, can support naturally in-plane hyperbolic polariton guided modes at mid-infrared frequencies without the need for patterning. This is possible because α-MoO3 is a biaxial hyperbolic crystal with three different Reststrahlen bands, each corresponding to a different crystalline axis. These findings can pave the way toward a new paradigm to manipulate and confine light in planar photonic devices.

Strong light-matter coupling manifested by Rabi splitting has attracted tremendous attention due to its fundamental importance in cavity quantum-electrodynamics research and great potentials in quantum information applications. A prerequisite for practical applications of the strong coupling in future optoelectronic devices is an all-solid-state system exhibiting room-temperature Rabi splitting with active control. Here we realized such a system in heterostructure consisted of monolayer WS and an individual plasmonic gold nanorod. By taking advantages of the small mode volume of the nanorod and large transition dipole moment of the WS exciton, giant Rabi splitting energies of 91-133 meV can be achieved at ambient conditions, which only involve a small number of excitons. The strong light-matter coupling can be dynamically tuned either by electrostatic gating or temperature scanning. These findings can pave the way toward active nanophotonic devices operating at room temperature.