共查询到20条相似文献,搜索用时 15 毫秒
1.
We investigate the third-order nonlinear optical properties of six novel fullerene derivatives under picosecond laser excitation by Z-scan technique. The experimental results reveal that all the derivatives have very large nonlinear absorption coefficient under 532 nm pulses excitation and great third-order nonlinear refraction index under 1064 nm pulses excitation. The molecular second hyperpolarizabilities are obtained from the experimental results. 相似文献
2.
Lei Gao Yanyan Huang 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(2):165-171
The effective linear and nonlinear optical properties of metal/dielectric composite media, in which ellipsoidal metal inclusions
are distributed in shape, are investigated. The shape distribution function P(L
x, L
y) is assumed to be 2Δ-2θ(L
x - 1/3 + Δ/3)θ(L
y - 1/3 + Δ/3)θ(2/3 + Δ/3 - L
x - L
y), where θ( . . . ) is the Heaviside function, Δ is the shape variance and Li are the depolarization factors of the ellipsoidal inclusions along i-symmetric axes (i = x, y). Within the spectral representation, we adopt Maxwell-Garnett type approximation to study the effect of shape variance Δ
on the effective nonlinear optical properties. Numerical results show that both the effective linear optical absorption α
∼ ωIm() and the modulus of the effective third-order optical nonlinearity enhancement |χ(3)
e|/χ(3)
1 exhibit the nonmonotonic behavior with Δ. Moreover, with increasing Δ, the optical absorption and the nonlinearity enhancement
bands become broad, accompanied with the decrease of their peaks. The adjustment of Δ from 0 to 1 allows us to examine the
crossover behavior from no separation to large separation between optical absorption and nonlinearity enhancement peaks. As
Δ → 0, i.e., the ellipsoidal shape deviates slightly from the spherical one, the dependence of |χ(3)
e|/χ(3)
1 on Δ becomes strong first and then weak with increasing the imaginary part of inclusions' dielectric constant. In the dilute
limit, the exact formula for the effective optical nonlinearity is derived, and the present approximation characterizes the
exact results better than old mean field one does.
Received 10 December 2002 Published online 4 June 2003
RID="a"
ID="a"e-mail: lgaophys@pub.sz.jsinfo.net 相似文献
3.
Spontaneous thermal expansion of nematic elastomers 总被引:1,自引:0,他引:1
We study the monodomain (single-crystal) nematic elastomer materials, all side-chain siloxane polymers with the same mesogenic
groups and crosslinking density, but differing in the type of crosslinking. Increasing the proportion of long di-functional
segments of main-chain nematic polymer, acting as network crosslinking, results in dramatic changes in the uniaxial equilibrium
thermal expansion on cooling from the isotropic phase. At higher concentration of main chains their behaviour dominates the
elastomer properties. At low concentration of main-chain material, we detect two distinct transitions at different temperatures,
one attributed to the main-chain, the other to the side-chain component. The effective uniaxial anisotropy of nematic rubber,
r(T) = / proportional to the effective nematic order parameter Q(T), is given by an average of the two components and thus reflects the two-transition nature of thermal expansion. The experimental
data is compared with the theoretical model of ideal nematic elastomers; applications in high-amplitude thermal actuators
are discussed in the end.
Received 25 June 2001 and Received in final form 29 September 2001 相似文献
4.
The third-order nonlinear optical properties of two fullerene derivatives under picosecond laser excitation have been investigated by Z-scan technique. The experimental results reveal that all the derivatives have very large nonlinear absorption coefficient under 532 nm pulses excitation and great third-order nonlinear refraction index under 1064 nm pulses excitation. The molecular second hyperpolarizabilities have been obtained from the experimental results. 相似文献
5.
We report on the ultrafast third-order optical nonlinearity in multilayer Au/TiO2 composite films fabricated on quartz substrates by pulsed laser deposition technique. The linear optical properties of the films are determined and optical absorption peaks due to surface plasmon resonance of Au particles are observed at about 590hm. The third-order optical nonlinearities of the films are investigated by z-scan method using a femtosecond laser (50 fs) at the wavelength of 800 nm. The sample showed fast nonlinear optical responses with nonlinear absorption coefficient and nonlinear refractive index being -3.66 × 10^-10 m/W and -2.95 × 10^-17 m^2/W, respectively. The results also show that the nonlinear optical effects increase with the increasing Au concentration in the composite films. 相似文献
6.
M. Dubiel S. Brunsch W. Seifert H. Hofmeister G.L. Tan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):229-232
Ag particles of 3.9 and 5.1 nm mean size in silicate glasses were produced by ion exchange and subsequent annealing at 480
and 600 °C. These thermal treatments may induce stresses in matrix and particles in addition to the well known effect of surface atoms
because of the thermal expansion mismatch of both materials. Structural characterisation of the particles by high-resolution
electron microscopy revealed a size-dependent lattice dilatation quite opposite to the so far observed lattice contraction
of similar metal/glass composites. This result, confirmed by X-ray absorption spectroscopy at the Ag K-edge, is discussed
in terms of an Ag-Ag bond length increase near the particle surface. The temperature-dependent EXAFS spectra (10-300 K) indicate
an increased thermal expansion coefficient of the particles with an increased mean particle size calculated on the basis of
an anharmonic Einstein model. With that the bond length increase can be explained. The results can be interpreted by a combination
of both the particle size effects and the influence of the surrounding matrix.
Received 30 November 2000 相似文献
7.
H. Kuzmany W. Plank M. Hulman Ch. Kramberger A. Grüneis Th. Pichler H. Peterlik H. Kataura Y. Achiba 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(3):307-320
We report on the evaluation of the distribution of diameters for nanotube samples with a wide variation of mean diameters.
Such results were obtained from a detailed analysis of the radial breathing mode Raman response and compared to results obtained
from an evaluation of optical spectra and X-ray diffraction pattern. The evaluation of the Raman data needs a well refined
analysis as the experimental analysis exhibits a rather complicated and oscillating relation between response and exciting
laser. Both, an exact calculation where the density of states was considered explicitly and an approximate calculation were
applied. Both models used for the analysis are able to explain several unexpected results from the experiment such as the
oscillating behavior of the spectral moments, unusual discontinuities in the first moments of the Raman response for excitation
in the IR, a fine structure for the response in optics and Raman, and an up shift of the RBM frequency as compared to qualified
ab initio calculations. In detail the first moment and the variance of the spectra were used for the evaluation of the diameter distribution.
To obtain good results between experimental and theoretical oscillation pattern the transition energy between the first two
van Hove singularities had to be scaled up which is considered as a result from coulomb interaction of the electrons in the
tubular material. On the other hand the analysis does not only allow to determine the mean value and the width of the diameter
distribution but yields also a value for the average bundle diameters or, alternatively, the strength of the tube-tube interaction.
The model used for the analysis of the Raman data is also appropriate to analyze the optical response, at least for the spectral
range from 0.5 eV to 3.5 eV. The fine structure in the response for the transitions between the three lowest van Hove singularities
is well reproduced and the mean tube diameters and their distribution is obtained in very good agreement with the results
from the Raman analysis. From the X-ray analysis the same mean values and comparable distributions for the tube diameters
were received whereas the bundle diameters could not be retained with high precision in this case.
Received 18 February 2001 and Received in final form 3 April 2001 相似文献
8.
P.L. Christiansen Y.B. Gaididei F.G. Mertens S.F. Mingaleev 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(4):545-553
We investigate the properties of nonlinear excitations in different types of soliton carrying systems with long-range dispersive interactions. We show that length-scale competition in such systems, universally results in a multi-component structure of nonlinear excitations
which may lead to a new type of multistability: coexistence of different nonlinear excitations at the same value of the spectral parameter (i.e., velocity in the case of anharmonic lattices or frequency in nonlinear Schr?dinger models).
Received 31 August 2000 and Received in final form 14 December 2000 相似文献
9.
10.
Gorce JP Bovey D McDonald PJ Palasz P Taylor D Keddie JL 《The European physical journal. E, Soft matter》2002,8(4):421-429
We present a systematic study of the vertical uniformity of water distribution during the drying of waterborne colloidal films,
testing the predictions of a Peclet number Pe defined for this system. Pe indicates the relative contributions of water evaporation and Brownian diffusion in determining the concentration profile
in the vertical direction (i.e. normal to the substrate). When Pe < 1, the water concentration in films cast from an alkyd emulsion is found via magnetic-resonance profiling to be uniform with depth, which is consistent with expectations. When Pe > 1, a gradient in the water concentration develops, with less water near the interface with air. The water profiles reveal
that the alkyd particles do not coalesce immediately upon contact in close-packing. At later times, a concentrated surface
layer develops, but particles are not coalesced in this layer to form a continuous “skin”, but rather the structure is likely
to be that of a biliquid foam.
Received 20 March 2002 and Received in final form 12 June 2002 相似文献
11.
The effect of oxidation on the structure of nickel nanoparticles 总被引:1,自引:0,他引:1
B. Rellinghaus S. Stappert E.F. Wassermann H. Sauer B. Spliethoff 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):249-252
The structural properties of nickel nanoparticles which are prepared by means of DC sputtering in argon and subsequently oxidized
in ambient air are reported. Ex situ structural and chemical investigations utilizing (high resolution) transmission electron microscopy and electron energy loss
spectroscopy reveal that the particles consist of a metallic core surrounded by an oxide shell. The lattice constant of the
nickel core is found to increase significantly with decreasing particle size. This widening of the nickel lattice is attributed
to an interfacial stress that originates from the lattice mismatch between nickel and nickel oxide.
Received 21 December 2000 相似文献
12.
R. Lazzari I. Simonsen D. Bedeaux J. Vlieger J. Jupille 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(2):267-284
The light scattering by three-dimensional clusters supported by a substrate is modelled by representing clusters by truncated
spheroids whose polarizability is calculated via a multipolar development of the potential in the quasi-static limit. The determination of the mean island radius, density
and aspect ratio from the optical response is examined. The strong influence of both the particle-substrate interaction and
the particle shape on the optical behaviour is demonstrated, showing the limits of effective medium and dipolar theories.
The Surface Differential Reflectance spectra of silver on MgO(100) and titanium or aluminium on α-Al2O3(0001) surfaces have then been modelled by using the above model, illustrating the capability of optical means to deal with
various metals, including those belonging to transition series. In all cases, it is highlighted that the aspect ratio is central
in modelling the optical response of supported particles.
Received 5 June 2000 and Received in final form 31 July 2001 相似文献
13.
Vicari L 《The European physical journal. E, Soft matter》2002,9(4):335-340
We present a new pump probe laser beams configuration for the nonlinear optical characterization of microemulsions. We detect
the variation of the on-axis optical intensity of the probe beam as generated by the concentration profile induced in an optically
thin film of microemulsion by the pump beam. A mathematical model has been introduced to describe the phenomenon. The technique
allows the determination of both Kerr-like optical nonlinearity and time constants and, therefore, it gives information both
on cluster dimension and their shape. We discuss its application to WAD (water/AOT/decane, where AOT denotes sodium-bis-di-ethyl-sulfosuccinate)
with the application of a strong electric field of optical source. Comparison between theoretical predictions and experimental
results confirms the presence of giant optical nonlinearity in the absence of turbidity divergence. Chainlike shape of clusters,
of the kind already reported with the application of strong electric field, could justify this result.
Received 26 October 2002
RID="a"
ID="a"e-mail: vicari@na.infn.it 相似文献
14.
G. Bour A. Reinholdt A. Stepanov C. Keutgen U. Kreibig 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):219-223
We studied the effect of hydrogen in yttrium nanoparticles on a quartz substrate, using optical spectroscopy and electrical
resistance measurements. Pulsed laser deposition is used to obtain the Y clusters in an UHV environment. We show, that these
clusters are highly sensitive to monoatomic H1 produced from ambient hydrogen gas pressures, ranging from 10-5 to 50 mbar with our experimental arrangement. The changes of optical and electrical properties due to the chemical reaction
within the particles are sufficient to consider this material as a possible sensor for low concentrations of hydrogen.
Received 29 November 2000 相似文献
15.
InP nanocrystals synthesized by refluxing and annealing of organic solvent are determined from XRD measurements to have an averse granularity of 25 nm. The nonlinear optical properties of the InP nanocrystals studied by using laser Z-scan technique with 50 ps pulses at 532nm are found to reveal strong nonlinear optical properties and two-photon absorption phenomenon. Also, the nonlinear absorption coeffcient, the nonlinear refractive index and the third-order nonlinear optical susceptibility are determined by experiments, in which the nonlinear refractive index is three orders of magnitude larger than that of bulk InP. 相似文献
16.
17.
S. Franke-Arnold S.M. Barnett G. Huyet C. Sailliot 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):373-383
We analyse the coherence properties of two particles trapped in a one-dimensional harmonic potential. This simple model allows
us to derive analytic expressions for the first and second order coherence functions. We investigate their properties depending
on the particle nature and the temperature of the quantum gas. We find that at zero temperature non-interacting bosons and
fermions show very different correlations, while they coincide for higher temperatures. We observe atom bunching for bosons
and atom anti-bunching for fermions. When the effect of s-wave scattering between bosons is taken into account, we find that the range of coherence is enhanced or reduced for repulsive
or attractive potentials, respectively. Strongly repelling bosons become in some way more “fermion-like" and show anti-bunching.
Their first order coherence function, however, differs from that for fermions.
Received 19 September 2002 Published online 4 February 2003 相似文献
18.
E.J.S. Fonseca E.A. Gouveia J.M. Hickmann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(1):75-78
We propose a new technique to perform measurements of nonlinearities in optical waveguides based on the variation of an optical
pulse chirp. This technique is analogous to the z-scan technique in the time domain. We analyze the new experimental method analytically and numerically, obtaining an useful
expression relating the nonlinearity with a peak-valley structure. Practical ways to implement the technique are discussed.
Received 13 March 2001 相似文献
19.
C. Egami Y. Suzuki O. Sugihara N. Okamoto H. Fujimura K. Nakagawa H. Fujiwara 《Applied physics. B, Lasers and optics》1997,64(4):471-478
We investigated the trans–cis photoisomerization of an azo dye in a rigid matrix and the resulting third-order resonant optical
nonlinearity by means of the simple theoretical prediction of a two-energy-level system, thin-layer chromatography and H-NMR
studies. A methylorange (MO), a methylred (MR), congored (CR) or a Disperse Red 1 (DR1) doped polyvinyl alcohol (PVA) or silica
film was used as nonlinear optical material. The existence of equi-absorbing points, or isosbestic points in the absorbance
spectrum change and the remarkable stationary transmittance to be independent of the action beam intensity enabled us to confirm
the photoisomerization even in a rigid matrix. Then, we measured the third-order resonant optical nonlinearity of dichroism
through the polarization absorbance spectrum measurement and determined the characteristic optical parameters of the photoisomerization
in the film such as the quantum yields φT, φC, the thermal reaction constant K and the photoisomerization time constant by fitting the theoretical curve of the two-energy-level system to the observed
temporal transmittance change after the action beam exposure of the MO/PVA film. The quantum yields were φˉT=0.36 and φˉC=0.38, respectively. The photoisomerization time constant of MO embedded in the PVA film was a few seconds. The thermal reaction
constant K depended on the excitation beam intensity.
Received: 20 June 1996/Revised version: 4 October 1996 相似文献
20.
Importance of lattice contraction in surface plasmon resonance shift for free and embedded silver particles 总被引:3,自引:0,他引:3
W. Cai H. Hofmeister M. Dubiel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(2):245-253
The size evolution of the surface plasmon resonance was investigated for free and embedded silver particles between about
2 to 10 nm in size. The crystal lattice of such particles as analyzed by high resolution electron microscopy show linear contraction
with reciprocal particle size. Based on this, a model was presented by combining the lattice contraction of particles and
the free path effect of electrons to predict the size evolution of the resonance. The results reveal a contribution of the
lattice contraction to the resonance shift according to a roughly linear relation that changes slightly with particle radius
(> 1.0 nm) and surrounding media. This surface plasmon resonance shift proceeds linearly with reciprocal size for Ag particles
in vacuum and argon, but for Ag particles embedded in glass it appears to be independent of the radius down to nearly 1 nm.
All predictions are quantitatively compared to previously reported experimental data and a good agreement is obtained. An
unusual red-shift observed for Ag particles in glass may be attributed to a thermal expansion mismatch induced lattice dilatation.
Received 26 July 2000 and Received in final form 14 September 2000 相似文献