共查询到20条相似文献,搜索用时 15 毫秒
1.
Using DCM dye grains and light of different wavelengths generated by two CW laser diodes that oscillate in the near-infrared
wavelength region, visible light emission from dye grains due to near-infrared excitation based on a nonadiabatic, nondegenerate
excitation process was observed for the first time. Unlike sum-frequency generation with nonlinear polarization, the difference
in polarization angles of the two beams did not affect the emitted light intensity. Optical sampling based on this nonadiabatic,
nondegenerate excitation principle was demonstrated for the first time. The optical pulse shape in the wavelength band of
λ=1250–1350 nm, which is close to the wavelength range used for optical fiber communications, was measured with a temporal
resolution of 0.8–1.1 ps. 相似文献
2.
Y. Lin M.H. Hong W.J. Wang Y.Z. Law T.C. Chong 《Applied Physics A: Materials Science & Processing》2005,80(3):461-465
We report direct laser writing of lithography patterns with a feature width of 20±5 nm on thin photoresist film by combining a double-frequency femtosecond laser and a near-field scanning optical microscope. The obtained feature size is much smaller than the laser wavelength () and the aperture diameter (d) with a resolution of /20 and d/2, respectively. The lithography patterns were analyzed with an atomic force microscope and a scanning electron microscope. The effects of laser energy and writing speed on the feature size were investigated. The underlying physical mechanism was also discussed. PACS 07.79.Fc; 07.79.Lh; 42.70.Jk; 68.37.Hk; 81.16.Nd 相似文献
3.
T. Miyanishi T. Sakai N. N. Nedyalkov M. Obara 《Applied Physics A: Materials Science & Processing》2009,96(4):843-850
Nanohole fabrication process with gold nanoparticles irradiated by femtosecond laser at different incident angles is investigated.
Nanoparticles with diameter of 200 nm and laser irradiation with center wavelength of 800 nm are used in the present study.
The analysis of the electromagnetic field distribution in the near-field zone of the particle is made by simulations based
on finite-differential time domain (FDTD) method. It is shown that when gold nanoparticle is irradiated by laser pulse surface
plasmon excitation can be induced, and associated with it, high-intensity near field is produced in a limited area around
the particle. It is found that the change of the irradiation conditions by means of irradiation from various incident directions
gives a possibility of laser nanoprocessing with tunable characteristics. Our results show that enhanced optical intensity
is able to be induced on the substrate surface regardless of incident direction of the laser due to the image charge interaction with the substrate. Furthermore, the use of p-polarized
laser irradiation at a certain angle gives a minimum of the spatial dimensions of the enhanced zone on the substrate which
is about two times smaller than that obtained at normal incidence. 相似文献
4.
H.-L. Lee W.-J. Chang Y.-C. Yang S.-S. Chu 《Applied physics. B, Lasers and optics》2009,97(3):653-659
The Timoshenko beam theory, including the effects of rotary inertia and shear deformation, is used to analyze the resonant
frequency of lateral vibration of scanning near-field optical microscope (SNOM) tapered probe with a laser-induced thermal
effect. In the analysis, the thermal effect can be considered as an axial force and is dependent of temperature distribution
of the probe. The Rayleigh–Ritz method is used to solve the vibration problem of the probe. According to the analysis, the
frequencies of the first three vibration modes increase when the thermal effect is taken into account. The effects of shear
deformation and rotary inertia on the frequency ratio of a Timoshenko beam to an Euler beam increase when the mode number
increases and the contact stiffness decreases. In addition, the frequency of mode 1 increases with increasing taper angle
and coating thickness of the probe. Comparison of the frequency of a SNOM probe coated with Al, Ag, or Au, the highest is
with Al coating, and the lowest is with Au coating. 相似文献
5.
M. K. Hossain Y. Kitahama G. G. Huang T. Kaneko Y. Ozaki 《Applied physics. B, Lasers and optics》2008,93(1):165-170
In this study, surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS) characteristics of gold nanoaggregates
with different morphologies are examined to elucidate the correlation between SPR and SERS of the object. Nanoaggregates,
defined as random aggregates (hereafter RA), elongated aggregates (hereafter EA) and two-dimensional layered aggregates (hereafter
2DLA) are fabricated by immobilizing colloidal gold nanoparticles on glass substrates. The color variation observed in the
RA and EA samples indicates the variation in localized SPR excitations excited on the samples. The RA sample mostly shows
a broadened and shifted SPR peak centered at 570 nm in addition to another peak in the longer wavelength region (∼700 nm),
whereas in the EA sample a weak blue-shifted peak is observed near 450 nm in addition to a broadened peak centered at 570 nm
covering a trail for another one near 700 nm. In the case of the 2DLA sample, more than one SPR peaks are observed in the
longer wavelength region. The SERS observation confirms million times higher enhancement at least in Raman intensity using
the gold nanoaggregates adsorbed by dye molecules. The EA sample of gold nanoparticles shows ∼5 times higher enhancement in
Raman signal compared to that of the RA and 2DLA sample. 相似文献
6.
Fresnel zone plates (FZPs) were fabricated in order to evaluate the performance of nonadiabatic photolithography by exploiting the localized nature of optical near fields. This novel photolithography scheme could realize FZPs with structures smaller than the wavelength of the light source used for exposure. The FZP for 325-nm-wavelength UV light could focus the incident light to a spot size of 590 nm. An FZP for focusing soft X-rays was also fabricated and, compared to conventional adiabatic photolithography, showed higher-contrast zones over the whole area of the FZP. This method exhibits a high dynamic range and good spatial resolution, and it was free from artifacts due to the interference of the residual propagating exposure light transmitted through the aperture of the photomask. 相似文献
7.
Photoassociation inside an optical dipole trap: absolute rate coefficients and Franck–Condon factors
We present quantitative measurements of the photoassociation of cesium molecules inside a far-detuned optical dipole trap. A model of the trap-depletion dynamics is derived which allows us to extract absolute photoassociation rate coefficients for the initial single-photon photoassociation step from measured trap-loss spectra. The sensitivity of this approach is demonstrated by measuring the Franck–Condon modulation of the weak photoassociation transitions into the low-vibrational levels of the outer well of the Og- state that correlates to the 6s+6p3/2 asymptote. The measurements are compared to theoretical predictions. In a magneto-optical trap, these transitions have previously only been observed indirectly through ionization of ground-state molecules. PACS 34.50.Rk; 33.70.Ca; 32.80.Pj 相似文献
8.
F. Muñoz J. Rogan G. García M. Ramírez J. A. Valdivia R. Ramírez M. Kiwi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,61(1):87-93
Collision processes between a single gold atom and a gold cluster are investigated by means of ab initio
techniques. The targets we consider are minimum energy 13 gold atom clusters. The kinetic energy of the
projectile and its impact parameter are chosen within a range such that the three regimes we are mainly
interested in studying (fusion, scattering and fragmentation) are realized. The results of the collision
processes are treated using density functional theory molecular dynamics (DFT-MD), analyzed in detail, and
compared with previous work, which was carried out using phenomenological potentials and classical molecular
dynamics. The differences between classical MD and DFT-MD are quite significant. 相似文献
9.
This paper reports that KI doped with Ce3+ or double doped with Tb3+ and Ce3+ were prepared by the Bridgman-Stockbarger method and characterized by optical absorption photoluminescence (PL), thermoluminescence (TL), photostimulated emission (PSL) and TL emission. The optical absorption measurement indicates that F and V1, V2 centers are formed in the crystals during the γ irradiation process. It was attempted to incorporate a broad band of Ce3+ activator into the narrow band emission of Tb3+ in the KI host without the reduction of emission intensity. Ce3+-co-doped KI and Tb crystals showed a broad band emission due to the d-f transition of Ce3+ and a reduction in the intensity of emission peaks due to the 5D3-7Fj (j=3,4,5,6) transition of Tb3+, when they were excited at 240 nm.These results supported that an effective energy transfer occurs from Tb3+ to Ce3+ in the KI host. Co-doping Ce3+ ions greatly intensified the excitation peak at 260 nm for the emission at 393 nm of Tb3+, which means that more lattice defects, involved in the energy absorption and transfer to Tb3+, are formed by the Ce3+ co-doping. The integrated light intensity is an order of magnitude higher as compared to the undoped samples for similar doses of irradiation and heating rates. The defects generated by irradiation were monitored by optical absorption and TSL Trap parameters for the TL process are calculated and presented. 相似文献
10.
M. Okida Y. Hayashi T. Omatsu J. Hamazaki R. Morita 《Applied physics. B, Lasers and optics》2009,95(1):69-73
We directly produced for the first time a high-power 1.06 μm vortex mode from a diode-pumped Nd:GdVO4 bounce amplifier. A maximum output of 17.8 W was achieved for a pump power of 55 W. The corresponding optical efficiency
from the diode to the output was above 30%. 相似文献
11.
A. Bolshakova I. Boyko G. Chelkov D. Dedovitch A. Elagin D. Emelyanov M. Gostkin A. Guskov Z. Kroumchtein Yu. Nefedov K. Nikolaev A. Zhemchugov F. Dydak J. Wotschack A. De Min V. Ammosov V. Gapienko V. Koreshev A. Semak Yu. Sviridov E. Usenko V. Zaets 《The European Physical Journal C - Particles and Fields》2010,70(3):543-553
We report on the comparison of production characteristics of secondary protons and charged pions in the interactions of protons and charged pions with momentum between 3 GeV/c and 15 GeV/c with beryllium, copper, and tantalum nuclei, with simulations by the FLUKA program and the Geant4 tool kit. Overall production cross-sections are reasonably well reproduced, within factors of two. In more detail, there are areas with poor agreement that are unsatisfactory and call for modelling improvements. Overall, the current FLUKA simulation fares better than the current Geant4 simulation. 相似文献
12.
N. Venkatram D. Narayana Rao L. Giribabu S. Venugopal Rao 《Applied physics. B, Lasers and optics》2008,91(1):149-156
We report our results on the nonlinear optical and optical limiting properties of two alkoxy phthalocyanines namely 2,3,9,10,16,17,23,24-octakis-(heptyloxy)
phthalocyanine and 2,3,9,10,16,17,23,24-octakis-(heptyloxy) phthalocyanine zinc(II) studied at a wavelength of 532 nm using
6 ns pulses. Using the standard Z-scan technique we observed that both the phthalocyanines exhibited negative nonlinearity
as revealed by the signature of closed aperture data. The magnitude of the nonlinear refractive index n2 evaluated from the closed aperture data was ∼ 1.61×10-11 cm2/W for the free-base phthalocyanine and ∼ 1.56×10-11 cm2/W for the metallic phthalocyanine. Open aperture Z-scan data indicates strong nonlinear absorption in both the phthalocyanines
with measured nonlinear coefficients of ∼ 1650 cm/GW and ∼ 1850 cm/GW respectively. We also report optical limiting properties
of these phthalocyanines with limiting thresholds (I1/2) of ∼ 0.5 J/cm2. Our studies suggest that these phthalocyanines are one of the best molecules for nonlinear optical applications studied
recently.
PACS 42.65.-k; 42.70.Jk, 42.65.Jx 相似文献
13.
Ekaterina Ponizovskaya Lars Thylen Alexander Bratkovsky Ying Fu 《Applied Physics A: Materials Science & Processing》2009,95(4):1029-1032
We study numerically and analytically a binary mixture of quantum dots exhibiting gain and loss. For a mixture of gain quantum
dots and silver nanoparticles, we find conditions when the composite shows negative dielectric constant operation and lossless operation. The composites of this kind may be used for dense integration of photonic components as well as modulation and
switching in optical interconnect systems
L. Thylen is also at Dept of Microelectronics and Applied Physics, Royal Institute of Technology (KTH), 164 40 Kista, Sweden. 相似文献
14.
The effects of dust temperature and the dust charge variation in a dusty plasma with vortex—like ion distribution 下载免费PDF全文
By considering both the dust temperature and the dust charge variation in dusty plasma with vortex-like ion distribution, we obtained a modified Korteweg-de Vries equation. It indicates that the effect of dust charge variation can cause the one-dimensional soliton amplitude to become larger, and the dust temperature can cause the soliton amplitude to become larger as well. Moreover, as the dust temperature increases, the soliton amplitude will increase. 相似文献
15.
16.
The transient microbending loss and refractive index changes in a double-coated optical fiber subjected to thermal loading
with stress-dependent interlayer thermal contact resistance is investigated. The effects of interlayer thermal resistance
on the transient microbending loss and refractive index changes of the optical fiber are analyzed and discussed. The results
show that the stress-dependent interlayer thermal contact resistance will increase the lateral pressure induced by the transient
thermal loading in the double-coated optical fiber and, thus, the microbending loss. Similarly, the interlayer thermal contact
resistance will increase the transient thermal loading induced refractive index changes in the beginning of loading. 相似文献
17.
Asmahani Awang S.K. Ghoshal M.R. Sahar M. Reza Dousti Raja J. Amjad Fakhra Nawaz 《Current Applied Physics》2013,13(8):1813-1818
Glasses with composition 70TeO2–20ZnO–10Na2O–0.5Er2O3–(x)Au are synthesized by melt-quenching technique. Their spectroscopic and optical characterizations are made. The presence of gold nanoparticles (Au NPs) with average size ~9 nm is confirmed from TEM micrograph. The value of Edir is found to lie between 3.082 and 3.073 eV, while Eindir lies within 2.765 to 2.724 eV. The observed visible up-conversion (UC) emission under 779 nm excitation wavelength exhibits two bands centered at 546 nm (green) and 637 nm (red) in all samples. The glass with 0.4 mol% Au NPs shows dominant enhancement in the UC emission intensity of the order of 3.5 times for the green band (4S3/2 → 4I15/2) and a weaker enhancement for the red (4F9/2 → 4I15/2) band. The optical properties of the system are affirmed to depend strongly on the Au concentration in the dielectric medium. The absorption spectra consist of six bands attributed to absorption from ground state (4I15/2) to 4I13/2, 4I11/2, 4I9/2, 4F9/2, 2H11/2, and 4F7/2 excited states. The structural reveals that the types of bonding and difference in electro-negativity can be manipulated by the presence of metallic NPs in glass matrix. Judd–Ofelt analysis asserts the increase in Ω2 and Ω6 parameters with the addition of Au NPs and the enhancement of green and red emissions. The enhancement is mainly attributed to large plasmonic effect of Au NPs. The proposed glasses can be nominated as potential materials for solid state laser developments. 相似文献
18.
The morphology of pentacene organic thin films deposited on SiO2 and Au(111) surfaces using organic molecular beam deposition (OMBD) has been characterized by a multi-technique approach.
Among the techniques applied were X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron
microscopy (SEM) and thermal desorption spectroscopy (TDS). Our rather detailed studies reveal that on both substrates the
growth is strongly influenced by dewetting and islanding phenomena, yielding very rough surfaces. Surprisingly, substantial
changes in the morphology were observed also after deposition on room-temperature samples on a time scale of several hours.
The rather extensive set of in situ XPS data was analyzed in the framework of a simple model, which allows us to derive rather
detailed information on the roughness parameters. 相似文献
19.
We are presenting a new low-cost Single Sideband (SSB) modulated Radio-over Fiber (RoF) communication system for millimeter (mm)-wave multiband wireless communication at the frequencies of 40 GHz, 80 GHz and 120 GHz. Its principle lies in the Carrier Suppressed modulation through a nested dual electrode Mach–Zehnder Modulator (MZM) and product modulator based baseband signal decomposition. In this novel method, the optical signal is decomposed into different SSB signals using a power splitter and product modulators at the base station. This proposed method uses a different technique for a baseband signal decomposition from the existing method. The proposed signal decomposition technique has reduced the nonlinearities due to the FBGs. The proposed method is compared with the existing method in terms of BER, data rate and OSNR. The simulation results disclose that our proposed scheme outperforms the existing methods at a higher data rate of 80 Gbps with a minimum BER and privileged Q factor. 相似文献
20.
Dependence of bimodal size distribution on temperature and optical properties of InAs quantum dots grown on vicinal GaAs (100) substrates by using MOCVD 下载免费PDF全文
Self-assembled InAs quantum dots (QDs) are grown on vicinal GaAs (100)
substrates by using metal-organic chemical vapour deposition (MOCVD). An
abnormal temperature dependence of bimodal size distribution of InAs quantum
dots is found. As the temperature increases, the density of the small dots
grows larger while the density of the large dots turns smaller, which is
contrary to the evolution of QDs on exact GaAs (100) substrates. This trend
is explained by taking into account the presence of multiatomic steps on the
substrates. The optical properties of InAs QDs on vicinal GaAs(100)
substrates are also studied by photoluminescence (PL) . It is found that
dots on a vicinal substrate have a longer emission wavelength, a narrower PL
line width and a much larger PL intensity. 相似文献