Stimulated Brillouin Scattering Enhancement Factor Improvement in a 11.6-GHz-Linewidth 1.5-kW Yb-Doped Fiber Amplifier

The stimulated Brillouin scattering （SBS） threshold enhancement factor in a pure white noise linewidth broad- ening Yb-doped fiber amplifier （YDFA） with a short large mode area fiber is theoretically and experimentally studied. We demonstrate a 1064.08nm, 11.6 GHz finewidth, 1.5 k W output power YDFA with an SBS threshold enhancement of -57 （26 W SBS threshold with single frequency seed）. The output beam is near-diffraction lim- ited with a beam quality factor elM2 = 1.15 and a slope efficiency of up to 87%. No SBS or stimulated Raman scattering effects are observed in the whole power range. Further power sealing is limited by the available pump power in our system.

Near-Field Scattering Enhancement of Perylene Based Aggregates for Random Lasing

Strong near-field scattering enhancement (NFSE) of polyhedral oligomeric silsesquioxanes(POSS) nanoparticles (NPs) aggregates is found through physical simulation. An aggregation of N,N′-di-[3-(isobutyl polyhedral oligomeric silsesquioxanes) propyl] perylene diimide(DPP) which possesses POSS as scatteres experimentally performs strong NFSE, which confirms the physical simulation results. Moreover, coherent random laser is triggered from the DPP aggregates in carbon disulfide. It is the NFSE of POSS NPs connected to both ends of DPP through covalent bonds and the NFSE of their aggregation thanks to DPP’s aggregation that is responsible for the coherent random laser. So, this work develops a method to improve weak scattering of system through construction of molecules, and opens a road to a variety of novel interdisciplinary investigations, involving molecular designing for disordered photonics.

Raman scattering enhancement characteristic of NbCl_5-and Nb_20_5-doped silica fibers

Two kinds of Nb-doped silica fibers, an NbCl5-doped fiber and an Nb205-doped fiber, are fabricated and char- acterized in this Letter. First, the refractive index profiles of both fibers are obtained, and then their Raman spectra are measured with 785 nm exciting light. The Nb-doped fibers＇ Raman spectra are compared with a conventional GeO2-doped single-mode silica fiber that is prepared with the same method and under the same conditions. As a result, the Raman gain coefficients of the Nb-doped silica fiber core are obtained. The exper- imental results show that Nb2O5 doping can enhance the Raman scattering intensity of the optical fibers.

Surface Enhanced Raman Scattering on Self-assembled Nano Silver Film Prepared by Electrolysis Method

We demonstrate surface enhanced Raman scattering （SERS） detection of self-assembled nano silver film using a low-cost electrolysis strategy at a proper voltage and silver nitrate concentration in electrolyte. The concentration dependence of SERS from crystal violet （CV） molecules adsorbed to silver film was systematically studied. Importantly, the SERS surface enhancement factor of such nano silver film was 603, which was measured by a portable Raman spectrometer. The minimum concentration of detectable CV molecules can be as low as 10^-11 mol/L. The nano silver film prepared by this electrolysis method is an active, stable, cost-effective, and reusable SERS substrate.

Green synthesis of MIL⁃101/Au composite particles and their sensitivity to Raman detection of thiram

Metal⁃organic framework(MOF)MIL⁃101 and surface plasmon polariton(SPP)supported gold nanoparti⁃cles(Au NPs)hybrid systems were developed as a highly sensitive and reproducible surface⁃enhanced Raman scat⁃tering(SERS)detection platform,in which a green electrostatic self⁃assembly technology was adopted to construct the substrate.In an aqueous solution,the electronegativity of the particles can be used to prepare the composite sub⁃strate without any surface modifier.Due to the enrichment capacity of MIL⁃101 and the electromagnetic enhance⁃ment from Au NPs,the well⁃designed MIL⁃101/Au composites possessed ultrahigh sensitivity with the detection limit of Rhodamine 6G(R6G)as low as 10^(-10) mol·L^(-1).Meanwhile,the substrate exhibits high stability,excellent reproduc⁃ibility,and recyclability.Additionally,the novel substrate can be explored for direct capture,and sensitively detect pesticide residues such as thiram.

EFFECT OF SOLVENT ON SURFACE ENHANCED RAMAN SCATTERING SPECTRA OF COLLOIDAL SILVER

The effect of solvent on surface enhanced Raman scattering [SERS) of colloidal silver has been studied. Experiments show that the intensity of SERS is related to the polarity and molecular constitution of the solvent. The influence of solvent is due to the change of the adsorption quantity and adsorption intensity.

Surface-enhanced Raman scattering properties of highly ordered self-assemblies of gold nanorods with different aspect ratios

Gold nanorods with aspect ratios of from 1 （particles） to 31.6 were synthesized by the seed-mediated method and packed in a highly ordered structure on a large scale on silicon substrates through capillary force induced self-assembly behaviour during solvent evaporation. The gold nanorod surface exhibits a strong enhancing effect on Raman scattering spectroscopy. The enhancement of Raman scattering for two model molecules （2-naphthalenethiol and rhodamine 6C） is about 5-6 orders of magnitude. By changing the aspect ratio of the Au nanorods, we found that the enhancement factors decreased with the increase of aspect ratios. The observed Raman scattering enhancement is strong and should be ascribed to the surface plasmon coupling between closely packed nanorods, which may result in huge local electromagnetic field enhancements in those confined junctions.

TiO_2/Ag composite nanowires for a recyclable surface enhanced Raman scattering substrate

Multifunctional TiO2/Ag composite nanowires are fabricated with a hydrothermal method by precipitating Ag nanoparticles （NPs） on the surfaces of TiO2 nanowires. This hierarchical one-dimensional （1D） nanostructure can be used as a surface enhanced Raman scattering （SERS） substrate with high sensitivity, for detecting the rhodamine 6G （R6G） in a wide range of low concentrations （from 1 × 10 6 M to 1 × 10-12 M）. In addition, the substrate can be self-cleaned under the irradiation of ultraviolet （UV） light due to the superior photocatalytic capacity of the TiO2/Ag composite nanostructure, making the recycled use of SERS substrates closer to reality. With both the evident SERS performance and high efficiency of photocatalytic capacity, such TiOz/Ag composite nanowires demonstrate considerable potential in the chemical sensing of organic pollutants.

Cascade correlation-enhanced Raman scattering in atomic vapors

A new Raman process can be used to realize efficient Raman frequency conversion by coherent feedback at low light intensity [Chen B, Zhang K, Bian C L, Qiu C, Yuan C H, Chen L Q, Ou Z Y, and Zhang W P 2013 Opt. Express 21, 10490]. We present a theoretical model to describe this enhanced Raman process, termed as cascade correlation-enhanced Raman scattering, which is a Raman process injected by a seeded light field. It is correlated with the initially prepared atomic spin excitation and driven by the quasi-standing-wave pump fields, and the processes are repeated until the Stokes intensities are saturated. Such an enhanced Raman scattering may find applications in quantum information, nonlinear optics, and optical metrology due to its simplicity.

STUDY ON PHOTO-INDUCED ORIENTATION OF A NOVEL PHOTO-ALIGNMENT FILM WITH SURFACE ENHANCED RAMAN SCATTERING (SERS) SPECTROSCOPY

Surface enhanced Raman scattering (SERS) spectroscopy was first utilized to study the photo-orientation behaviour of the photoreactive groups on a novel photo-alignment film surface and elucidate the generation mechanism of pretilt angle. The novel photo-alignment film was prepared by spin-coating a solution of ladderlike polysiloxane (LPS) bearing dual photoreactive group on an ITO surface and by irradiation with linear-polarized ultraviolet (LPUV) light A Si—H terminal compound (M) containing an identical photosensitive part has been used to fabricate a model film for SERS investigation.

Monitoring the penetration and accumulation of gold nanoparticles in rat skin ex vivo using surface-enhanced Raman scattering spectroscopy

Contamination by accidental cutaneous contact with the commercial products and the air pol-hutants raised a considerable health and safety issue.This study aimed to trace the dynamics of the 20 nm gold nanopartide(GNP)penetration and accumulation in rat skin tissues using a surface-enhanced Raman scattering(SERS)techmique.After the topical application of GNPs on rat skin surface,the SERS spectra were recorded for every 15 pum to an overall depth of 75 pum from skin surface for 150 min.The processes of GNP penetration in rat skin were accompanied by aggregation of GNPs,which affected SERS spectra.The results revealed that 20 nm GNPs can penetrate through stratum corneum layer,viable epidermis layer,and then into dermis layer.This study demonstrated for the first time the potential of SERS spectroscopy to monitor the penetration and accumulation of GNPs in rat skin.

SURFACE ENHANCED RAMAN SCATTERING OF C_(60) FILMS ON VARIOUS ACTIVE SUBSTRATES

In this paper,we report the study of surface-enhanced Raman Scattering of C_(60)films on roughed Ag,Cu and glass surface.The experiment results indicate that the C_(60)films on Ag substrate possess large enhance effect.An explanation of the enhancement with roughed glass surface is proposed based on waveguide Raman Scattering.

THE OBSERVATION OF ENHANCED RAMAN SCATTERING OF GASEOUS MOLECULES BY Hg MICRODROPLETS

ABSTRACT The Raman intensitics of gas molecules were found to be enormously enhanced in the presence of Hg-microdroplets.The enhancement factor for the molecules studied was found to be over 20.

Controllable Electrochemical Synthesis of Silver Dendritic Nanostructures and Their SERS Properties

Ag dendritic nanostructures were synthesized on fluorine-doped tin oxide covered glass sub- strates by the electrodeposition method. Results demonstrate that the size, diameter, crys- tallinity, and branch density of the Ag dendrites can be controlled by the applied potential, the surfactants and the concentration of AgNO3. Three kinds of typical silver dendrites were applied as substrates of the surface enhanced Raman scattering （SERS） and one of them was able to clearly detect rhodamine 6G concentrations up to 0.1 nmol/L. The differences of the SERS spectra at these Ag dendrites confirmed that the shapes and interparticle spacings have great effect on Raman enhancement, especially the interparticle spacings.

In-situ growth of silver nanostructure on quartz glass substrates

Silver nanostructure compact aggregates on the surface of quartz glass substrates were synthesized by small gold seeds with the assistance of poly vinypyrrolidone (PVP) and irradiation of fluorescent lamp. The formation mechanism of silver nanostructure was proposed. The results show that both the PVP and the light irradiation are the keys to in-situ growth of silver nanostructure on quartz glass substrates. The silver nanostructure of the substrates which finally grow up to 150 nm after 20 h irradiation exhibits irregular shape, and some of nanoparticles stack to form bilayer. A new broad band appears in the absorption spectra of the substrates due to the interparticle dipole?dipole coupling of surface plasmon resonance response of the triangular silver nanoplate particles, which red shifts 600?800 nm as the particles grow up. The substrates have an emission band centered at 400 nm on their fluorescence spectra, and the fluorescence intensity shrinks as the average size of the silver nanostructure increases. The strongest SERS signal of SERS-active substrate is fabricated after 16 h.

Construction of Au@Metal-organic framework for sensitive determination of creatinine in urine

Creatinine level in urine is an important biomarker for renal function diseases,such as renal failure,glomerulonephritis,and chronic nephritis.The Au@MIL-101(Fe)was prepared by in situ growth of Au nanoparticles in MIL-101(Fe)as a selective SERS substrate.The Au@MIL-101(Fe)offers the great local surface plasmon resonance(SPR)effect due to gold nanoparticles aggre-gation inside metal-organic frameworks.The framework structure could enrich trace target samples and drag them into SPR hot spots.The optimal Au@MIL-101(Fe)composite substrate is used for analyzing creatinine in urine and the limit of detection is down to 0.1μmol/L and a linear relationship is ranging from 1μmol/L to 100μmol/L.

THE RING OPENING REACTION OF AN EPOXY COMPOUND ON THE TOP OF CHEMISORBED CYSTAMINE STUDIED BY THE SERS TECHNIQUE

Metal foils for Raman scattering were prepared by HNO_3 etching method. These foils werefound to exhibit a strong SERS effect and excellent thermal stability. SERS spectra of cystaminehave been taken to illustrate the usefulness of this sample preparation method in the studies ofchemisorption. The ring opening reactions of an epoxy compound have been observed on the topof chemisorbed cystamine on silver foils.

Influence of local environment on the intensity of the localized surface plasmon polariton of Ag nanoparticles

A combined Ag nanoparticle with an insulating or conductive layer structure has been designed tor molecular detection using surface enhanced Raman scattering microscopy. Optical absorption studies revealed localized surface plasmon resonance, which shows regular red shift with increasing environmental dielectric constant. With the combined structure of surface enhanced Raman scattering substrates and rhodamine 6C as a test molecule, the results in this paper show that the absorption has a linear relationship with the local electromagnetic field for insulating substrates, and the electrical property of the substrate has a non-negligible effect on the intensity of the local electromagnetic field and hence the Raman enhancement.

Preparation of SiO_2@Au nanorod array as novel surface enhanced Raman substrate for trace pollutants detection

An effective surface enhanced Raman scattering（SERS） substrate is designed and fabricated by synthesis of Si O2 nanorods array via glancing angle deposition, followed by coating Au nanoparticles onto Si O2 surface in order to create numerous ＂hot spots＂. The detecting sensitivity of such substrate could be optimized by simply adjusting the deposition time of Au. Thus, it can be used for detection of Rhodamine 6G at concentration as low as 10^-9M. Furthermore, our SERS substrate is applied to detect 5 μg/g polychlorinated biphenyls in soil sample, which proves its potential for trace environmental pollutants detection.

STUDY ON THE CONCENTRATION DEPENDENCE OF ORIENTATION OF POLYSTYRENE ON SILVER BY THE SERS TECHNIQUE

Polystyrene films were adsorbed onto a silver surface from dichloromethane solutions with concentrations of 0.1 to 12 wt%, and then studied by the surface enhanced Raman technique. A critical concentration for coil interpenetration was observed.