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1.
Second-harmonic generation (SHG) in atmospheric-pressure air is experimentally studied using single focused linear-polarized
Ti:sapphire intense femtosecond laser pulses at 810 nm. The efficiency of SHG is found to reach a maximum at the optical breakdown
threshold of ≈2.9×1014 W/cm2. The spectral distribution and polarization property of the second harmonic are investigated. The contribution to SHG from
electric-field-induced third-order mixing plays the main role even after the optical breakdown had occurred.
Received: 23 May 2000 / Published online: 16 August 2000 相似文献
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M.F. Plass C. Popov B. Ivanov S. Mändl M. Jelinek L.M. Zambov W. Kulisch 《Applied Physics A: Materials Science & Processing》2001,72(1):21-27
Amorphous nitrogen-rich carbon nitride (CNx) films have been prepared by inductively coupled plasma chemical vapour deposition (ICP-CVD) utilizing transport reactions
from a solid carbon source. The nitrogen atomic fraction N/(C+N) is about 1 or even higher as detected by various surface
and bulk sensitive methods. An investigation of the chemical bonding structure showed that the films are composed of >C=N
units with a small fraction of C≡N groups. Based on these findings, several structural units derived from cis- and trans-conjugated
carbon–nitrogen chains are proposed. The optical properties of the CNx films were studied by transmission spectroscopy and spectral ellipsometry; the optical Tauc gap was determined to 2.1±0.05 eV.
The photoluminescence characteristics were measured at three different excitation wavelengths (476, 488 and 515 nm) and revealed
two individual contributions. These data are interpreted in terms of the different structural units comprising the nitrogen-rich
CNx films.
Received: 14 July 2000 / Accepted:17 July 2000 / Published online: 22 November 2000 相似文献
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P.G. Kevrekidis B.A. Malomed Z. Musslimani 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(3):421-436
A model including two nonlinear chains with linear and nonlinear couplings between them, and opposite signs of the discrete
diffraction inside the chains, is introduced. In the case of the cubic [ χ(3)] nonlinearity, the model finds two different interpretations in terms of optical waveguide arrays, based on the diffraction-management
concept. A continuum limit of the model is tantamount to a dual-core nonlinear optical fiber with opposite signs of dispersions
in the two cores. Simultaneously, the system is equivalent to a formal discretization of the standard model of nonlinear optical
fibers equipped with the Bragg grating. A straightforward discrete second-harmonic-generation [ χ(2)] model, with opposite signs of the diffraction at the fundamental and second harmonics, is introduced too. Starting from
the anti-continuum (AC) limit, soliton solutions in the χ(3) model are found, both above the phonon band and inside the gap. Solitons above the gap may be stable as long as they exist,
but in the transition to the continuum limit they inevitably disappear. On the contrary, solitons inside the gap persist all
the way up to the continuum limit. In the zero-mismatch case, they lose their stability long before reaching the continuum
limit, but finite mismatch can have a stabilizing effect on them. A special procedure is developed to find discrete counterparts
of the Bragg-grating gap solitons. It is concluded that they exist at all the values of the coupling constant, but are stable
only in the AC and continuum limits. Solitons are also found in the χ(2) model. They start as stable solutions, but then lose their stability. Direct numerical simulations in the cases of instability
reveal a variety of scenarios, including spontaneous transformation of the solitons into breather-like states, destruction
of one of the components (in favor of the other), and symmetry-breaking effects. Quasi-periodic, as well as more complex,
time dependences of the soliton amplitudes are also observed as a result of the instability development.
Received 14 September 2002 / Received in final form 4 February 2003 Published online 24 April 2003
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ID="a"e-mail: malomed@eng.tau.ac.il 相似文献
6.
Nonlinear optical response of Ge nanocrystals in silica matrix with excitation of femtosecond pulses
H.P. Li C.H. Kam Y.L. Lam Y.X. Jie W. Ji A.T.S. Wee C.H.A. Huan 《Applied physics. B, Lasers and optics》2001,72(5):611-615
We report an investigation of third-order optical nonlinearities in Ge nanocrystals (∼6 nm radius) embedded in silica matrix
using the Z-scan and pump-probe techniques with femtosecond laser pulses at 780-nm wavelength. The nanocrystallite Ge samples
were prepared using magnetron co-sputtering and post-thermal annealing at 800 °C. The nonlinear absorption coefficient and
refractive index of the Ge nanocrystals were determined to be in the range from 1.8×10-7 to 6.8×10-7 cm/W and 1.5×10-12 to 8.0×10-12 cm2/W, respectively, which are proportional to the Ge atomic fraction in the matrix. Relaxation of the nonlinear response was
found to have two characteristic time constants, 1.8 ps and 65 ps. The mechanisms responsible for the observed nonlinear response
are discussed.
Received: 21 August 2000 / Revised version: 17 January 2001 / Published online: 30 March 2001 相似文献
7.
New materials for optical cooling 总被引:3,自引:0,他引:3
Well-characterized solid-state laser materials are evaluated for performance in optical refrigeration as well as radiation-balanced
laser systems. New figures-of-merit are developed and applied to ytterbium-doped materials. Superior performance is predicted
for high-cross-section tungstate materials. Photothermal deflection experiments on samples of Yb3+-doped KGd(WO4)2 confirm anti-Stokes fluorescence cooling. This is the first observation of optical cooling in a crystal.
Received: 1 February 2000 / Revised version: 15 June 2000 / Published online: 13 September 2000 相似文献
8.
Efficient and compact intracavity-frequency-doubled Nd:GdVO4/KTP laser end-pumped by a fiber-coupled laser diode 总被引:2,自引:0,他引:2
D.Y. Shen H.R. Yang J.G. Liu S.C. Tam Y.L. Lam W.J. Xie J.H. Gu K. Ueda 《Applied physics. B, Lasers and optics》2001,72(3):263-266
A compact and efficient diode-pumped intracavity-frequency-doubled Nd:GdVO4/KTP green laser is demonstrated with a flat–flat cavity design. With a 1.3 at. % Nd3+-doped GdVO4 crystal and pumped at the weak-absorption peak of 806 nm, the second-harmonic output power at 532 nm was measured to be 1.95 W
at an incident pump power of 8.4 W, corresponding to an optical conversion efficiency of 23.2%. The output characteristic
at the fundamental wavelength of 1.063 μm was investigated with two different pump wavelengths. More than 4.5-W output power
was generated when the laser was pumped at 806.2 nm.
Received: 26 July 2000 / Revised version: 18 September 2000 / Published online: 7 February 2001 相似文献
9.
Propagation of light through localized coupled-cavity modes in one-dimensional photonic band-gap structures 总被引:2,自引:0,他引:2
M. Bayindir S. Tanriseven E. Ozbay 《Applied Physics A: Materials Science & Processing》2001,72(1):117-119
We report on the observation of a new type of propagation mechanism through evanescent coupled optical cavity modes in one-dimensional
photonic crystals. The crystal is fabricated from alternating silicon-oxide/silicon-nitride pairs with silicon-oxide cavity
layers. We achieved nearly full transmission throughout the guiding band of the periodic coupled cavities within the photonic
band gap. The tight-binding (TB) parameter κ is determined from experimental results, and the dispersion relation, group velocity
and photon lifetime corresponding to the coupled-cavity structures are analyzed within the TB approximation. The measurements
are in good agreement with transfer-matrix-method simulations and predictions of the TB photon picture.
Received: 21 August 2000 / Revised version: 22 August 2000 / Published online: 9 November 2000 相似文献
10.
C. Li J. Boyaval M. Warenghem P. Carette 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(3):449-456
We report operation of a Nd3+-doped fiber-laser using a cholesteric liquid crystal acting as a narrow band reflector. The aim of this work is to apply
to a fiber-laser the particular optical properties of an helical structure, whatever is the medium exhibiting this structure,
either a liquid crystal or either any other material. The advantage of the use of these mediums in the design of fiber-lasers
is that they can favourably take the place, in an easy and compact way, of several optical elements such as a polarizer and
a quarter-wave plate at one and the same time. This technology promises to design rugged compact low cost tunable coherent
sources the lasing range of which can easily be adjusted. We emphasize here the particular part played by the cholesteric
liquid crystal-glass interface in the laser action of the fiber.
Received 21 October 1999 and Received in final form 7 February 2000 相似文献
11.
Th. Cabioc'h S. Camelio L. Henrard Ph. Lambin 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(3):535-540
Concentric-shell fullerenes, also called carbon onions, produced by carbon ion implantation into silver thin films, and subsequently
deposited on a silica substrate, were studied by optical transmission spectroscopy in the wavelength range 0.2 - 1.2 μm. In
this interval, the strongest absorption is due to the π-plasmon of sp2-like carbon. The position of the plasmon absorption band clearly evolved from 265 nm at low fluence to 230 nm at high implantation
fluences. A simulation of the optical spectra based on dielectric models of the concentric-shell fullerenes layer allowed
us to identify the first peak as due to disordered graphite and the latter to the carbon onions. The concentration of residual
graphite and the filling fraction of the carbon onions produced at high fluences could be estimated by fitting the optical
spectra with computed transmittance curves.
Received 13 July 2000 相似文献
12.
Sol-gel-derived pyroelectric barium strontium titanate thin films for infrared detector applications 总被引:3,自引:0,他引:3
J.-G. Cheng J. Tang A.-J. Zhang X.-J. Meng J.-H. Chu 《Applied Physics A: Materials Science & Processing》2000,71(6):667-670
Quality pyroelectric Ba0.8Sr0.2TiO3 films have been successfully fabricated by a sol-gel processing using a highly diluted precursor solution. The remnant polarization
of the films decreases with the temperature increasing, which results in a large pyroelectric coefficient at room temperature.
Infrared response measured using a 500-K chopped blackbody at room temperature exhibits a typical pyroelectric response waveform.
Frequency dependence of the infrared response measurement for a pixel with area of 2.5×10-3 cm2 showed that the maximum response output voltage of 3.2 mV was obtained at 6 Hz. Better infrared response can be expected
by the improvement in thermal isolation of the pixels and electrode materials.
Received: 26 April 2000 / Accepted: 9 May 2000 / Published online: 9 August 2000 相似文献
13.
C.J. da Silva M.T. de Araujo E.A. Gouveia A.S. Gouveia-Neto 《Applied physics. B, Lasers and optics》2000,70(2):185-188
The temperature effect upon infrared-to-visible frequency upconversion fluorescence emission in Yb3+-sensitized Er3+-doped germanosilicate optical fibers excited with cw radiation at 1.064 μm is investigated. The experimental results revealed
an eightfold enhancement in the visible upconversion emission intensity as the fiber temperature was increased from 17 °C
to 180 °C. The fluorescence emission enhancement is attributed to the temperature-dependent multiphonon-assisted anti-Stokes
excitation process of the ytterbium sensitizer. A theoretical approach that takes into account a sensitizer absorption cross-section,
which depends on the phonon occupation number, has proven to agree very well with the experimental data
Received: 6 April 1999 / Revised version: 27 August 1999 / Published online: 27 January 2000 相似文献
14.
G. Toci M. Vannini R. Salimbeni M.A. Dubinskii E. Giorgetti 《Applied physics. B, Lasers and optics》2000,71(6):907-910
We report the results of the first measurements of the non-linear Kerr refractive index, n2, for LiBaF3 and LiLuF4 crystal hosts, known as prospective UV-emitting tunable laser media when doped with Ce3+ ions. These n2 values (2.7×10-16 and 1.5×10-16 cm2/W at 532 nm, respectively), obtained using the well-established Z-scan technique, are important for the characterization
of new optical materials particularly in relation to their potential ultrafast applications.
Received: 6 June 2000 / Published online: 5 October 2000 相似文献
15.
P.M. Visser G. Grynberg 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(3):403-413
A probed optical lattice is modelled as a driven anharmonic oscillator with noise. For specific values of the probe intensity
and detuning, atoms are forced in bistable solutions. The friction and fluctuations that arise from laser cooling, determine
the equilibrium between these two modes of vibration. The distribution determines the absorption spectrum and the transient
emission spectrum that is emitted by the optical lattice after the probe has been switched off.
Received 23 May 2000 and Received in final form 17 August 2000 相似文献
16.
E. Chappel M.D. Núñez-Regueiro F. Dupont G. Chouteau C. Darie A. Sulpice 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(4):609-614
Magnetisation measurements up to 23 T and submillimeter wave ESR in the frequency region 48-380 GHz have been performed on
NaNiO2 powders at low temperature. Also typical spectra above the Néel temperature are shown. At 4 K the magnetisation shows a spin-flop transition at 1.8 T and saturation at 10 T. /Ni confirms the low spin state of the Ni3+ ions. The susceptibility exhibits a maximum at K with and K. NaNiO2 is an A-type antiferromagnet: we derive K and K for the interactions between Ni ions within and between adjacent layers, respectively. The AFMR spectra yield an energy
gap of 52.5 GHz, in agreement with the spin-flop value derived from the magnetisation. The anisotropy of the g factor observed at 100 K with can be attributed to the Jahn-Teller effect for Ni3+ ions in the low spin state, which stabilises the occupation. We finally comment on the isomorphic controversial Li1-xNi1+xO2 compound.
Received 9 March 2000 and Received in final form 13 July 2000. 相似文献
17.
R.M. Xie H.B. Fu X.H. Ji Z.H. Chen J.N. Yao 《Applied Physics A: Materials Science & Processing》2002,74(2):239-242
4,4′-dibromobiphenyl nanocrystals with different sizes in the range from 20 nm to 300 nm were prepared by the reprecipitation
method. It was found that their absorption peaks experienced a red shift while the size of the nanocrystals increased. Through
analyzing these spectra of the nanocrystals with different sizes, it is suggested that this size-dependent optical property
is contributed by two factors, the size effect and the J-aggregate formation.
Received: 28 August 2000 / Accepted: 2 March 2001 / Published online: 23 May 2001 相似文献
18.
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
19.
Effect of thermal undulations on the bending elasticity and spontaneous curvature of fluid membranes
We amplify previous arguments why mean curvature should be used as measure of integration in calculating the effective bending
rigidity of fluid membranes subjected to a weak background curvature. The stiffening of the membrane by its fluctuations,
recently derived for spherical shapes, is recovered for cylindrical curvature. Employing curvilinear coordinates, we then
discuss stiffening for arbitrary shapes, confirm that the elastic modulus of Gaussian curvature is not renormalized in the
presence of fluctuations, and show for the first time that any spontaneous curvature also remains unchanged.
Received 19 April 1999 and in Received in final form 7 January 2000 相似文献
20.
T. Döppner S. Teuber M. Schumacher J. Tiggesbäumker K.H. Meiwes-Broer 《Applied physics. B, Lasers and optics》2000,71(3):357-360
Clusters of heavy metal atoms in strong femtosecond laser-light fields undergo multi-ionization with the loss of hundreds
of electrons. The cross section largely exceeds that of corresponding isolated atoms, which leads in the case of PbN to a complete ionization of the 4f shell with a light intensity of 1.2×1015 W/cm2. Experimental investigations on Pb and Pt clusters with variable pulse widths and, for the first time, with the pump&probe
technique give insight into the dynamics of the coupling of electromagnetic radiation into the clusters. Both approaches support
the picture according to which, after an initial charging, the clusters expand due to Coulomb forces. This expansion is accompanied
by a reduction of the electron density and at the same time by an increase of the optical sensitivity. Once the plasmon energy
of the diluted nanoplasma approaches the photon energy, the charging efficiency increases significantly. The experimental
observations are confirmed by random-phase approximation (RPA) calculations of the optical response, including molecular-dynamics
simulations of the expanding systems.
Received: 11 November 1999 / Published online: 13 July 2000 相似文献