共查询到20条相似文献,搜索用时 31 毫秒
1.
C. Keller J. Schmiedmayer A. Zeilinger T. Nonn S. Dürr G. Rempe 《Applied physics. B, Lasers and optics》1999,69(4):303-309
We report experiments on the diffraction of atoms from a standing light wave in the channeling regime, characterized by long
interaction time and large potential height. The observed far-field diffraction patterns depend specifically on the way in
which the potential is switched on and off. For fast switching, the evolution is non-adiabatic and many diffraction orders
are populated. For slow switching, however, the evolution is adiabatic and the number of populated diffraction orders decreases
dramatically. The experiments are performed in two different setups employing rubidium and argon atoms, respectively. In one
of the setups, we study the dependence of the diffraction pattern on the interaction time, in the other setup that on the
incidence angle.
Received: 30 November 1998 / Revised version: 5 July 1999 / Published online: 8 September 1999 相似文献
2.
We report on the observation of a multiple-pattern stability region in a photorefractive single-feedback system. Whereas hexagonal
patterns are predominant for feedback with positive diffraction length we show that a variety of stable non-hexagonal patterns
are generated for certain negative diffraction lengths. For the same values of the control parameters square, rectangular,
or squeezed hexagonal patterns are found alternating in time. Besides these pure states, we found a number of different mixed-pattern
states. We review the linear stability analysis for this system and show that the special shape of the threshold curves in
the investigated parameter region gives a first explanation for the occurrence of a multiple-pattern region.
Received: 22 June 1999 / Revised version: 30 August 1999 / Published online: 3 November 1999 相似文献
3.
V. Turco Liveri M. Rossi G. D’Arrigo D. Manno G. Micocci 《Applied Physics A: Materials Science & Processing》1999,69(4):369-373
ZnS nanoparticles were synthetized using water-containing AOT reversed micelles as nanoreactors and characterized by UV-Vis
spectrophotometry, HRTEM (high-resolution transmission electron microscopy), SAED (selected-area electron diffraction), and
digital image processing. The experimental data evidence a slow growing process of fractal-like ZnS nanoparticles’ coupled
with a change of their photophysical properties. Both these processes are well described by power laws. The nanoparticles
size is mainly controlled by the micellar size. After evaporation of the organic solvent, it has been found that the deposit
is constituted by smaller and more stable ZnS nanoparticles bathed in a surfactant matrix.
Received: 20 April 1999 / Accepted: 23 April 1999 / Published online: 8 September 1999 相似文献
4.
M. Weber F. Rickermann F. Abbing G. von Bally 《Applied physics. B, Lasers and optics》1999,68(5):1069-1072
A holographic double-exposure interferometer for quasi real-time analysis is realized, utilizing a photorefractive BTO:Cd
crystal for hologram recording. Heating of the crystal reduces the time required to reach the steady-state working situation.
Light-induced absorption losses are reduced by heating as well. Additionally, the diffraction efficiency is increased by this
method. A sixfold increase in the light intensity of the reconstructed interferogram is achieved.
Received: 2 December 1998 / Revised version: 28 January 1999 / Published online: 7 April 1999 相似文献
5.
The interplay of diffraction dissociation and nuclear shakeoff is considered in a schematic but still realistic model for
the case of the break-up of halo nuclei on light targets. We demonstrate that the shakeoff effect, arising from the momentum
imparted by the core diffraction, is small but still identifiable in the experimental data for the dissociation of the one-
and two-neutron halo nuclei 11Be and 11Li.
Received: 29 October 1999 / Revised version: 15 January 2000 相似文献
6.
G. Kuri 《Applied Physics A: Materials Science & Processing》1999,68(6):699-703
Analytical electron microscopy, high-resolution X-ray diffraction and combined Rutherford backscattering spectrometry and
channeling experiments have been used to investigate the radiation damage and the effect of post-implantation annealing on
the microstructure of GaAs(100) single crystals implanted with 1.00 MeV Cu+ ions to a dose of ≈ 3×1016 cm-2 at room temperature. The experiments reveal the formation of a thick and continuous amorphous layer in the as-implanted state.
Annealing up to 600 °C for 60 min does not result in the complete recovery of the lattice order. The residual disorder in
GaAs has been found to be mostly microtwins and stacking fault bundles. The redistribution of implanted atoms during annealing
results in the formation of nano-sized Cu particles in the GaAs matrix. The X-ray diffraction result shows a cube-on-cube
orientation of the Cu particles with the GaAs lattice. The depth distribution and size of the Cu particles have been determined
from the experimental data. A tentative explanation for these results is presented.
Received: 15 February 1999 / Accepted: 18 February 1999 / Published online: 28 April 1999 相似文献
7.
T. Füller M. Konuma J. Zipprich F. Banhart 《Applied Physics A: Materials Science & Processing》1999,69(6):597-603
Silicon-germanium layers are grown from metallic solution on (100) and (111) silicon substrates. On (111) Si, coherently strained
dislocation-free SiGe layers are obtained with thicknesses larger than predicted by the current models of misfit-induced strain
relaxation. A comprehensive characterisation by imaging, diffraction, and analytical electron microscopy techniques is carried
out to determine the critical thickness, study the onset of plastic relaxation, and explain the particular growth mechanisms
leading to an unexpectedly high thickness of elastically strained SiGe layers. A vertical Ge concentration gradient and the
formation of step edges on the layers, where lateral strain relaxes locally, explain the high critical thickness. The model
of Matthews and Blakeslee is modified in order to match the experimental observations for solution-grown SiGe layers.
Received: 29 July 1999 / Accepted: 29 July 1999 / Published online: 27 October 1999 相似文献
8.
Photoluminescence in anatase titanium dioxide nanocrystals 总被引:7,自引:0,他引:7
Titanium dioxide (TiO2) nanocrystals were prepared by a hydrolysis process of tetrabutyl titanate. X-ray diffraction and Raman scattering showed
that the as-prepared TiO2 nanocrystals have anatase structure of TiO2, and that the monophase anatase nanocrystals can be achieved through a series of annealing treatments below 650 °C. We measured
photoluminescence (PL) spectra of the TiO2 nanocrystals. Under 2.41–2.71 eV laser irradiation, the TiO2 nanocrystals displayed strong visible light emission with maxima of 2.15–2.29 eV even at excitation power as low as 0.06 W/cm2. To identify the PL mechanism in the TiO2 nanocrystals, the dependences of the PL intensity on excitation power and irradiation time were investigated. The experimental
results indicated that the radiative recombination is mediated by localized levels related to surface defects residing in
TiO2 nanocrystallites.
Received: 7 April 1999 / Revised version: 23 August 1999 / Published online: 30 November 1999 相似文献
9.
H.L. Bai E.Y. Jiang P. Wu Z.D. Lou Y. Wang C.D. Wang 《Applied Physics A: Materials Science & Processing》1999,69(6):641-647
The structural characterization of heat-treated CN films fabricated by dual-facing-target sputtering for soft X-ray multilayer
mirrors was performed by means of X-ray diffraction (XRD), Raman spectroscopy (RS) and X-ray photoelectron spectroscopy (XPS).
The XRD analyses indicate a graphization process in the CN films during thermal annealing. The Raman analyses imply that the
primary bonding in the CN films is sp2. In other words, the formation of the sp3 bonding in the CN films can be suppressed effectively by doping with N atoms, and thus the thickness expansion resulting
from the changes in the density of CN films during annealing can be decreased considerably. This result is also clarified
by the increased conductivity measured. The XPS results give the information of the existence of the strong covalent bonding
between N and C atoms, which can slow down the tendency of the structural relaxation during annealing. These results suggest
that CN films suitable for soft X-ray multilayers used at high-temperature environments can be obtained by reactive dual-facing-target
sputtering. With the low-angle X-ray diffraction measurements, we do observe the enhanced thermal stability of CoN/CN multilayers.
Received: 2 October 1998 / Accepted: 21 April 1999 / Published online: 23 September 1999 相似文献
10.
We present the development of a holographic interferometer that uses a photorefractive crystal of the sillenite family as
holographic recording medium. The aim of this work is to achieve a transportable and breadboard instrument, with a flexible
design and which is user friendly for the quantified measurements of displacements on large scattering objects. The state
of the art of the use of photorefractive crystals in holographic interferometry is presented. Based on the latter, a method
that is the best suited to our mentioned objectives is chosen: the real-time interferometric technique associated with the
crystal configuration exhibiting diffraction anisotropy. On this basis, we have studied and compared two imaging systems,
we have experimentally determined the holographic figures of merit of three sillenite crystals samples, and, finally, we have
shown the use of two measurement quantification methods. The result of these investigations is a certified and transportable
holographic camera prototype containing all the necessary equipment for its operation, which can be easily adapted to various
applications. Among these, we show its use in the detection of defects in composite structures, in the measurement of time-evolving
deformations, and in the measurement of vibration modes.
Received: 4 December 1998 / Revised version: 6 March 1999 / Published online: 12 April 1999 相似文献
11.
S. Schloter A. Schreiber M. Grasruck A. Leopold M. Kol’chenko J. Pan C. Hohle P. Strohriegl S.J. Zilker D. Haarer 《Applied physics. B, Lasers and optics》1999,68(5):899-906
We present a detailed study of the photoelectric as well as the holographic properties of a novel organic photorefractive
glass based on triphenylamine. We studied the quantum efficiency Φ of the photogeneration of charges by means of photoinduced
discharge measurements. The photoconductivity σ and the charge carrier mobility μ were obtained via dc photoconduction and
pulsed time-of-flight experiments, respectively. The holographic characterization was performed by two-wave and degenerate
four-wave mixing experiments allowing for the determination of properties such as diffraction efficiency η, modulation of
the refractive index Δn, gain coefficient Γ, and phase-shift φp of the investigated system. The experimental data for Φ could be successfully described by the Onsager formalism with a thermalization
radius of r0=24 ? and a primary quantum yield of Φ0=40%. We evaluated the E field and temperature-dependent measurements of μ using the B?ssler formalism yielding a width of
the density of states of σ=0.13 eV and a disorder parameter Σ=3.6. On this basis the lifetime and the average drift length
of the charge carriers could be estimated from the dc photoconduction experiments. From the photoelectric measurements we
also calculated the holographic response time that matched very well to the measured response time and described the E-field
dependence satisfactorily. The presented photorefractive system shows outstanding optical properties and stability with respect
to degradation. We measured a gain coefficient of Γ=90 cm-1, and a diffraction efficiency of η=27% at a response time of 30 ms for only 40-μm-thick samples. Orientational enhancement
was observed and evaluated quantitatively. To our knowledge, this work presents the first determination of each of the above
quantities all in one single organic photorefractive material.
Received: 16 November 1998 / Revised version: 4 January 1999 / Published online: 31 March 1999 相似文献
12.
Nanocrystalline GaSb embedded in SiO2 films was grown by radio-frequency magnetron co-sputtering. X-ray diffraction pattern and transmission electron microscopy
(TEM) confirm the existence of GaSb nanocrystals in the SiO2 matrix. The average size of GaSb nanoparticles is in the range of 3 to 11 nm. Diffuse reflectance spectra were used to characterize
the small change of the band gap of the semiconductor. The diffuse reflectance spectra shows that the absorption peaks have
a large blueshift of about 4.0 eV of the absorption relative to that of bulk GaSb. It has been explained by quantum confinement
effects. Room temperature optical transmission spectra show that the absorption edge exhibits a very large blueshift of about
2.1 eV with respect to that of bulk GaSb in agreement with quantum confinement.
Received: 28 July 1999 / Accepted: 27 October 1999 / Published online: 1 March 2000 相似文献
13.
Permanent holographic recording in indium oxide thin films using 193 nm excimer laser radiation 总被引:2,自引:0,他引:2
S. Pissadakis S. Mailis L. Reekie J.S. Wilkinson R.W. Eason N.A. Vainos K. Moschovis G. Kiriakidis 《Applied Physics A: Materials Science & Processing》1999,69(3):333-336
Permanent holographic recording in sputtered indium oxide (InOx) thin films is demonstrated, using ultraviolet radiation at 193 nm emitted by an ArF excimer laser. Steady-state refractive
index changes of up to 5×10-3 are calculated from the measured diffraction efficiency of a HeNe laser probe beam. The recorded gratings exhibit a dynamic
behaviour that relaxes to a steady-state value that depends on the oxygen partial pressure used during growth and on the recording
beam intensity. The observed behaviour is explained in terms of laser-induced structural changes.
Received: 12 October 1998 / Accepted: 8 March 1999 / Published online: 4 August 1999 相似文献
14.
P. Zahl P. Kury M. Horn von Hoegen 《Applied Physics A: Materials Science & Processing》1999,69(5):481-488
Lattice-mismatch-induced surface or film stress has significant influence on the morphology of heteroepitaxial films. This
is demonstrated using Sb surfactant-mediated epitaxy of Ge on Si(111). The surfactant forces a two-dimensional growth of a
continous Ge film instead of islanding. Two qualitatively different growth regimes are observed. Elastic relaxation: Prior to the generation of strain-relieving defects the Ge film grows pseudomorphically with the Si lattice constant and
is under strong compressive stress. The Ge film relieves strain by forming a rough surface on a nm scale which allows partial
elastic relaxation towards the Ge bulk lattice constant. The unfavorable increase of surface area is outbalanced by the large
decrease of strain energy. The change of film stress and surface morphology is monitored in situ during deposition at elevated
temperature with surface stress-induced optical deflection and high-resolution spot profile analysis low-energy electron diffraction.
Plastic relaxation: After a critical thickness the generation of dislocations is initiated. The rough phase acts as a nucleation center for
dislocations. On Si(111) those misfit dislocations are arranged in a threefold quasi periodic array at the interface that
accommodate exactly the different lattice constants of Ge and Si.
Received: 1 April 1999 / Accepted: 17 August 1999 / Published online: 6 October 1999 相似文献
15.
S. Rols E. Anglaret J.L. Sauvajol G. Coddens A.J. Dianoux 《Applied Physics A: Materials Science & Processing》1999,69(6):591-596
Elastic and inelastic neutron scattering are used to study the structure and dynamics of single-wall carbon nanotubes (SWNT)
self-assembled into nanobundles (NBSWNT). Suspensions of NBSWNT are characterized by small-angle neutron scattering. Neutron
diffraction is used as a useful tool to study the structure of both the SWNT and NBSWNT. Calculations on finite-size bundles
are compared to the data in order to estimate the distribution of tube diameters. Finally, we present time of flight inelastic
scattering measurements of the phonon density of states and discuss the main features of the spectra in comparison with calculations.
Received: 9 June 1999 / Accepted: 3 August 1999 / Published online: 27 October 1999 相似文献
16.
A. Thompson N. Nazhestkina A. Siahmakoun G. Duree N. Roesler 《Applied physics. B, Lasers and optics》2003,76(5):547-554
We present experimental investigations of electrical fixing techniques in Ce:SBN:60. The effect of crystal fatigue on the
diffraction efficiency of electrically fixed photorefractive gratings is studied. We observed that applying an ac field to
the crystal eliminated crystal fatigue and improved diffraction efficiency. A controllable diffraction efficiency of a photorefractive
grating is presented. A reproducible diffraction efficiency of up to 75% is obtained using a write-reveal grating technique
with high-voltage pulses of opposite polarity. We also show that the diffraction efficiency can be controlled by varying the
intensity of the writing beams incident to the crystal during the recording process. A method of determining the hysteresis
loop using the domain-fixing technique is proposed. The dependence of the diffraction efficiency on the direction of the applied
electric field while writing the hologram is studied. Our experiments show that, during writing, when the electric field is
applied opposite to the c axis the grating can be successfully revealed with both positive and negative dc voltages. However,
when the grating is written with a field parallel to the c axis, the grating can be revealed only with a field applied in
the opposite direction.
Received: 28 October 2002 / Revised version: 28 February 2003 / Published online: 14 May 2003
RID="*"
ID="*"Corresponding author. Fax: +1-812/872-6167, E-mail: azad.siahmakoun@rose-hulman.edu 相似文献
17.
F. Lison D. Haubrich P. Schuh D. Meschede 《Applied physics. B, Lasers and optics》1999,69(5-6):501-504
We have demonstrated the partly directed reflection of a slow cesium atomic beam by using the natural magnetic stray field
above a Nd-Fe-B surface. From these experiments we determine the reflectivity and a minimum value for the magnetic stray field
directly at the surface.
Received: 5 July 1999 / Revised version: 6 October 1999 / Published online: 3 November 1999 相似文献
18.
We propose a new method for the generation of single photons. Our scheme will lead to the emission of one photon into a single
mode of the radiation field in response to a trigger event. This photon is emitted from an atom strongly coupled to a high-finesse
optical cavity, and the trigger is a classical light pulse. The device combines cavity-QED with an adiabatic transfer technique.
We simulate this process numerically and show that it is possible to control the temporal behaviour of the photon emission
probability by the shape and the detuning of the trigger pulse. An extension of the scheme with a reloading mechanism will
allow one to emit a bit-stream of photons at a given rate.
Received: 7 July 1999 / Revised version: 3 September 1999 / Published online: 20 October 1999 相似文献
19.
Atom lasers based on rf-outcoupling can be described by a set of coupled generalized Gross–Pitaevskii equations (GPE). We
compare the theoretical predictions obtained by numerically integrating the time-dependent GPE of an effective one-dimensional
model with recently measured experimental data for the F=2 and F=1 states of Rb-87. We conclude that the output of a rf atom-laser can be described by this model in a satisfactory way.
Received: 15 June 1999 / Revised version: 9 September 1999 / Published online: 10 November 1999 相似文献
20.
Atom lithography with a cold, metastable neon beam 总被引:1,自引:0,他引:1
P. Engels S. Salewski H. Levsen K. Sengstock W. Ertmer 《Applied physics. B, Lasers and optics》1999,69(5-6):407-412
We study different aspects of atom lithography with metastable neon atoms. Proximity printing of stencil masks is used to
test suitable resists that are sensitive to the internal energy of the atoms, including dodecanethiols on gold and octadecyltrichlorosilanes
grown on a SiO2 surface. As an example of patterning the atomic beam with laser light, we create parallel line structures on the surface
with a periodicity of half the laser wavelength by locally de-exciting the atoms in a standing quenching wave.
Received: 29 June 1999 / Revised version: 30 August 1999 / Published online: 10 November 1999 相似文献