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Y. R. Shen

Bio: Y. R. Shen is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: Liquid crystal & Monolayer. The author has an hindex of 98, co-authored 476 publications receiving 37313 citations. Previous affiliations of Y. R. Shen include University of Paris & Harvard University.


Papers
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Journal ArticleDOI
TL;DR: Phase-sensitive sum-frequency spectroscopy provides correct characterization of vibrational resonances of water-vapor interfaces and allows better identification of interfacial water species contributing to different parts of the spectra.
Abstract: Phase-sensitive sum-frequency spectroscopy provides correct characterization of vibrational resonances of water-vapor interfaces and allows better identification of interfacial water species contributing to different parts of the spectra. Iodine ions emerging at an interface create a surface field that tends to reorient the more loosely bonded water molecules below the topmost layer.

297 citations

Journal ArticleDOI
TL;DR: Optical second harmonic and sum-frequency generation has been proven to be a very versitile probe for surface and interface studies as mentioned in this paper, and a brief account is given on how the technique was developed and numerous applications found in our laboratory.

289 citations

Journal ArticleDOI
TL;DR: In this article, optical second-harmonic generation was used to study the local field enhancement due to surface roughness on various materials ranging from the alkalis to a semiconductor, and the results were used to predict some rather substantial enhancements for surface Raman scattering for a number of substrate materials.
Abstract: Optical second-harmonic generation was used to study the local-field enhancement due to surface roughness on various materials ranging from the alkalis to a semiconductor. The roughness morphology was standardized by evaporating each material onto the same chemically etched glass slide, having microstructures hundreds to thousands of angstroms in size. With the laser excitation at 1.06 ..mu..m, the observed second-harmonic enhancements for different materials varied from 27 to 1 x 10/sup -3/ times that of silver. They were in fair agreement with a simple model calculation assuming that the rough surface is composed of a distribution of noninteracting hemispheroids on a plane. The results are used to predict some rather substantial enhancements for surface Raman scattering for a number of substrate materials.

282 citations

Journal Article
TL;DR: Agranovich et al. as mentioned in this paper discussed linear and nonlinear optical wave propagation in a left-handed medium (LHM) or medium of negative refraction (NRM) using the approach of characterizing the medium response totally by a generalized electric polarization (with a dielectric r permittivity e ( ω, k ) that can be decomposed into a curl and a non-curl part.
Abstract: Linear and Nonlinear Wave Propagation in Negative Refraction Meta-Materials V. M. Agranovich 1,2) , Y. R. Shen 3) , R. H. Baughman 1) , A. A. Zakhidov 1) UTD-NanoTech Institute,The University of Texas at Dallas, Richardson TX, 75083-0688 USA Institute of Spectroscopy, Russian Academy of Sciences, Troitsk, Moscow obl. 142190, Russia Physics Department, University of California, Berkeley, CA 94720 USA ABSTRACT We discuss linear and nonlinear optical wave propagation in a left-handed medium (LHM) or medium of negative refraction (NRM). We use the approach of characterizing the medium response totally by a generalized electric polarization (with a dielectric r permittivity e ( ω , k ) ) that can be decomposed into a curl and a non-curl part. The description has a one-to-one correspondence with the usual approach characterizing the LHM response with a dielectric permittivity e <0 and a magnetic permeability μ <0. The latter approach is less physically transparent in the optical frequency region because the usual definition of magnetization loses its physical meaning. Linear wave propagation in LHM or NRM is characterized by negative refraction and negative group velocity that could be clearly manifested by ultra-short pulse propagation in such a medium. Nonlinear optical effects in LHM can be predicted from the same calculations adopted for ordinary media using our general approach. I. Introduction. Over 30 years ago, Veselago [1] suggested that electromagnetic wave propagation in an isotropic medium with negative dielectric permittivity, e ( ω ) < 0 and negative magnetic permeability μ ( ω ) < 0 can exhibit very unusual properties. Since in such r r r media, the wave vector k , the electric field E , and the magnetic field H of a wave form a left-handed orthogonal set, in contrast to the right- handed orthogonal set in an ordinary medium, they are sometimes labeled as left-handed meta-materials (LHM), as opposite to the ordinary right-handed media (RHM). Among the many interesting properties of wave propagation in such media are the appearances of a Pointing vector in the direction

276 citations

Journal ArticleDOI
TL;DR: By folding exfoliated MoS2 monolayers-MoS2 bilayers with different stacking orders, this work provides an effective and versatile means to engineer transition-metal dichalcogenide materials with desirable electronic and optical properties.
Abstract: Folding MoS2 monolayers to obtain bilayers with different stacking orders results in enhanced valley- and spin-polarizations compared with natural Bernal-stacked bilayers.

268 citations


Cited by
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01 May 1993
TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.
Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

29,323 citations

Journal ArticleDOI
TL;DR: A review of gold nanoparticles can be found in this article, where the most stable metal nanoparticles, called gold colloids (AuNPs), have been used for catalysis and biology applications.
Abstract: Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

11,752 citations

Journal ArticleDOI
TL;DR: In this paper, the authors describe recent progress in the theory of nanoparticle optical properties, particularly methods for solving Maxwell's equations for light scattering from particles of arbitrary shape in a complex environment.
Abstract: The optical properties of metal nanoparticles have long been of interest in physical chemistry, starting with Faraday's investigations of colloidal gold in the middle 1800s. More recently, new lithographic techniques as well as improvements to classical wet chemistry methods have made it possible to synthesize noble metal nanoparticles with a wide range of sizes, shapes, and dielectric environments. In this feature article, we describe recent progress in the theory of nanoparticle optical properties, particularly methods for solving Maxwell's equations for light scattering from particles of arbitrary shape in a complex environment. Included is a description of the qualitative features of dipole and quadrupole plasmon resonances for spherical particles; a discussion of analytical and numerical methods for calculating extinction and scattering cross-sections, local fields, and other optical properties for nonspherical particles; and a survey of applications to problems of recent interest involving triangula...

9,086 citations

Journal ArticleDOI
Ulrike Diebold1
TL;DR: Titanium dioxide is the most investigated single-crystalline system in the surface science of metal oxides, and the literature on rutile (1.1) and anatase surfaces is reviewed in this paper.

7,056 citations

Journal ArticleDOI
TL;DR: Graphene has high mobility and optical transparency, in addition to flexibility, robustness and environmental stability as discussed by the authors, and its true potential lies in photonics and optoelectronics, where the combination of its unique optical and electronic properties can be fully exploited, even in the absence of a bandgap, and the linear dispersion of the Dirac electrons enables ultrawideband tunability.
Abstract: The richness of optical and electronic properties of graphene attracts enormous interest. Graphene has high mobility and optical transparency, in addition to flexibility, robustness and environmental stability. So far, the main focus has been on fundamental physics and electronic devices. However, we believe its true potential lies in photonics and optoelectronics, where the combination of its unique optical and electronic properties can be fully exploited, even in the absence of a bandgap, and the linear dispersion of the Dirac electrons enables ultrawideband tunability. The rise of graphene in photonics and optoelectronics is shown by several recent results, ranging from solar cells and light-emitting devices to touch screens, photodetectors and ultrafast lasers. Here we review the state-of-the-art in this emerging field.

6,863 citations