Optical computing has been pursued for decades as a potential strategy for advancing beyond the fundamental performance limitations of semiconductor-based electronic devices, but feasible on-chip integrated logic units and cascade devices have not been reported. Here we demonstrate that a plasmonic binary NOR gate, a 'universal logic gate', can be realized through cascaded OR and NOT gates in four-terminal plasmonic nanowire networks. This finding provides a path for the development of novel nanophotonic on-chip processor architectures for future optical computing technologies.

We show that the local electric field distribution of propagating plasmons along silver nanowires can be imaged by coating the nanowires with a layer of quantum dots, held off the surface of the nanowire by a nanoscale dielectric spacer layer. In simple networks of silver nanowires with two optical inputs, control of the optical polarization and phase of the input fields directs the guided waves to a specific nanowire output. The QD-luminescent images of these structures reveal that a complete family of phase-dependent, interferometric logic functions can be performed on these simple networks. These results show the potential for plasmonic waveguides to support compact interferometric logic operations.

GPS displacement vectors show that the crust in east Tibet is being squeezed in an easterly direction by the northward motion of the Indian plate, and the Sichuan Basin is resisting this stream and redirecting it mainly towards Indochina. The Longmen Shan, containing the steepest rise to the high plateau anywhere in Tibet, results from the strong interaction between the east Tibetan escape flow and the rigid Yangtze block (Sichuan Basin), but the kinematics and dynamics of this interaction are still the subject of some debates. We herein present results from a dense passive-source seismic profile from the Sichuan Basin into eastern Tibet in order to study the deep structure of this collision zone. Using P and S receiver function

[1] We analyse receiver functions from 29 broad-band seismographs along a 380-km profile across the Longmenshan (LMS) fault belt to determine crustal structure beneath the east Tibetan margin and Sichuan basin. The Moho deepens from about 50 km under Songpan -Ganzi in east Tibet to about 60 km beneath the LMS and then shallows to about 35 km under the western Sichuan basin. The average crustal Vp/Vs ratios vary in the range 1.75 -1.88 under Songpan -Ganzi in east Tibet, 1.8 -2.0 under the LMS, and decrease systematically across the NW part of the Sichuan basin to less than 1.70. A negative phase arrival above the Moho under SongpanGanzi and Sichuan basin is interpreted as a PS conversion from the top of a low-velocity layer in the lower crust. The very high crustal Vp/Vs ratio and negative polarity PS conversion at the top of lower crust in east Tibet are inferred to be seismic signatures of a low-viscosity channel in the eastern margin of the Tibetan plateau. The lateral variation of Moho topography, crustal Vp/Vs ratio and negative polarity PS conversion at the top of the lower crust along the profile seem consistent with a model of lower crust flow or tectonic escape. Citation:

No abstract

We perform a finite-frequency tomographic inversion to image 3D velocity structures beneath southern and central Tibet using teleseismic body-wave data recorded by the TIBET-31N passive seismic array as well as waveforms from previous temporary seismic arrays. High-velocity bodies dip ~40° northward beneath the Himalaya and the Lhasa Terrane. We interpret these high-velocity anomalies as subducting Indian Continental Lithosphere (ICL). The ICL appears to extend further north in central Tibet than in eastern Tibet, reaching 350 km depth at ~31°N along 85°E but at ~30°N along 91°E. Low P-and S-wave velocity anomalies extend from the lower crust to ≥180 km depth beneath the Tangra Yum Co Rift, Yadong-Gulu Rift, and the Cona Rift, suggesting that rifting in southern Tibet may involve the entire lithosphere. The anomaly beneath Tangra Yum Co Rift extends down to about 180 km, whereas the anomalies west of the Yadong-Gulu Rift and east of the Cona Rift extend to more than 300 km depth. The low-velocity upper mantle west of the Yadong-Gulu Rift extends furthest north and appears to connect with the extensive upper-mantle low-velocity region beneath central Tibet. Thus the northward-subducting Indian Plate is fragmented along north-south breaks that permit or induce asthenospheric upwellings indistinguishable from the upper mantle of northern Tibet.

Surface plasmons, the quanta of the collective oscillations of free electrons at metal surface, can be easily tuned by changing the surrounding dielectric materials, which is well known for metal nanoparticles and metal surfaces, but less is known for one-dimensional metal nanowires. Here, we find an extremely large tunability of surface plasmons on Ag nanowires with a beat period of the near-field distribution pattern increasing by 90 nm per nanometer of Al 2 O 3 coating, or by 16 μm per refractive index unit change in the surrounding medium. Such high sensitivity is crucial to directly control the optical signal distribution for various routing and demultiplexing functions in plasmonic circuits and may pave the way to the development of on-chip ultrasensitive biosensing.he miniaturization of optical devices to the scale compatible with modern nanoelectronic circuits demands the ability to manipulate light at the subwavelength scale. Recently, plasmonics has been a rapidly emerging field that offers various means to manipulate light at the nanometer scale using surface plasmons (SPs) (1-10). SPs can strongly confine electromagnetic fields near metal-dielectric interface to overcome the conventional diffraction limit of dielectric optics. Therefore, SP-based nanophotonic devices are promising to build densely on-chip integrated circuits for next-generation information technology (11,12). The scaling down of photonic circuits may find applications in quantum information processing as well (13,14). It is known that the properties of SPs can be strongly affected by the surrounding dielectric materials, e.g., the refractive index of the surrounding material determines the dispersion relations and resonance energies of SPs (15). Although the sensitivity of localized SPs on various metal nanostructures to local dielectric environments has been well studied, less is known for the cases of propagating SPs in plasmonic circuits. It is a challenge to develop advanced plasmonic modulation schemes for designing simple, robust metal-dielectric heteronanostructures suitable for highperformance on-chip plasmonic circuits.Plasmonic waveguide is one of the key elements for the plasmonic circuits. Different nanostructures have been investigated as waveguides (16)(17)(18)(19)(20)(21)(22)(23)(24). Chemically synthesized crystalline silver nanowires (Ag NWs) can support propagating SPs (25-28) with lower losses than lithographically defined NW waveguides (29), and can be easily manipulated to construct complex optical devices (30-33), which make them ideal candidates for proofof-principle studies of plasmonic circuits. Metal NWs of diameters of tens to hundreds of nanometers and lengths of several to tens of micrometers are mesoscopic systems, which show many novel and valuable properties and may potentially be used in many fields. To investigate the SP propagating properties in metal NWs, both near-field optical microscopy and quantum dots (QDs) fluorescence imaging where QDs are used as local field reporters were applied to produc...

A series of novel ionic liquids, 2-aminoethanol tetrafluoroborate ([MEA]and 2-[2-hydroxyethyl(methyl)amino] ethanol sulfate ([MDEA][SO 4 ]), were synthesized and characterized for carbon dioxide capture in this work. Densities and viscosities of ionic liquids (1-butyl-3-methylimidazolium tetrafluoroborate, [MEA][BF 4 ], [MDEA][BF 4 ], [MDEA][Cl], [MDEA][PO 4 ], and [MDEA][SO 4 ]), amines + ionic liquids + H 2 O, ionic liquids + H 2 O, and amines + H 2 O were measured at temperatures ranging from (303.15 to 343.15) K at different mass fractions. These 16 different absorbents were prepared by mixing two or three compounds of 2-aminoethanol (MEA), 2-[2-hydroxyethyl(methyl)amino] ethanol (MDEA), 2-[bis(2hydroxyethyl)amino] ethanol (TEA), ionic liquids, and water. The carbon dioxide capture rate and carbon dioxide capture capacity in the 16 different absorbents were measured at 303.15 K and 1.50 MPa. The experimental results showed that the viscosities of these absorbents are less than 17.00 mPa • s at 303.15 K. Among these absorbents, the MDEA + [MDEA][Cl] + H 2 O + piperazine system shows the best performance on carbon dioxide capture.