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1.
We investigate the properties of two separate dipole traps, realised using a cw mode-locked Ti:sapphire laser and a cw mode-locked
Nd:YVO4 laser, red-detuned by 25 nm and 284 nm, respectively. Approximately 103 laser-cooled 85Rb atoms were confined in the traps at ≈50 μK, with no observable heating after initial loading. The lifetimes of the traps
were consistent with limitations imposed by wavelength-dependent photoassociation losses and collisions with background vapour.
Determination of the ac Stark shift of the 780 nm cooling transition using a weak probe beam showed no observable difference
between using narrow-bandwidth or mode-locked trapping light. Techniques for trapping and focusing of atoms based on the dipole
force of blue and uv light become much more accessible through efficient doubling, tripling and quadrupling of mode-locked
sources. This opens up the possibility of manipulating more technologically interesting species.
Received: 30 September 1999 / Revised version: 21 December 1999 / Published online: 24 March 2000 相似文献
2.
A. di Stefano D. Wilkowski J.H. Müller E. Arimondo 《Applied physics. B, Lasers and optics》1999,69(4):263-268
We have operated a magneto-optical trap and optical molasses for the laser cooling of cesium atoms on the basis of a five-beam
laser configuration. For the magneto-optical trap two laser beams counterpropagate along the axis of a quadrupole trap and
the remaining three beams propagate in the orthogonal plane at 120° to each other. The same optical configuration was used
for the optical molasses. We have tested the efficiency in atom collection and the temperatures reached in both cooling processes.
In comparison to previous results on a six-beam configuration, a lower number of atoms is collected, while comparable densities
are realized. The atomic temperatures have been measured through a delayed shadow-image technique, where one of the running-wave
cooling beams produces an absorptive image of the atoms on a camera.
Received: 14 January 1999 / revised version: 23 June 1999 / Published online: 8 September 1999 相似文献
3.
R.A. Gunasekaran J.D. Pedarnig M. Dinescu 《Applied Physics A: Materials Science & Processing》1999,69(6):621-624
A parametric study of the growth of La0.5Sr0.5CoO3 (LSCO) thin films on (100) MgO substrates by pulsed-laser deposition (PLD) is reported. Films are grown under a wide range
of substrate temperature (450–800 °C), oxygen pressure (0.1–0.9 mbar), and incident laser fluence (0.8–2.6 J/cm2). The optimum ranges of temperature, oxygen pressure, and laser fluence to produce c-axis oriented films with smooth surface morphology and high metallic conductivity are identified. Films deposited at low
temperature (500 °C) and post-annealed in situ at higher temperatures (600–800 °C) are also investigated with respect to their
structure, surface morphology, and electrical conductivity.
Received: 20 November 1998 / Accepted: 6 July 1999 / Published online: 21 October 1999 相似文献
4.
K.Y. Lim Y.S. Lee Y.D. Chung I.W. Lyo C.N. Whang J.Y. Won H.J. Kang 《Applied Physics A: Materials Science & Processing》2000,70(4):431-434
In this study, the grain boundary diffusion of Cu through a TiN layer with columnar structure was investigated by X-ray photoelectron
spectroscopy (XPS). It was observed that Cu atoms diffuse from the Cu layer to the surface along the grain boundaries in the
TiN layer at elevated temperature. In order to estimate the grain boundary diffusion constants, we used the surface accumulation
method. The diffusivity of Cu through TiN layer with columnar structure from 400 °C to 650 °C is Db≈6×10−11exp(−0.29/(kBT )) cm2/s.
Received: 18 May 1999 / Accepted: 8 September 1999 / Published online: 23 February 2000 相似文献
5.
K. Morgenstern E. Laegsgaard I. Stensgaard F. Besenbacher M. Böhringer W.-D. Schneider R. Berndt F. Mauri A. De Vita R. Car 《Applied Physics A: Materials Science & Processing》1999,69(5):559-569
We investigate atomic and molecular nanostructures on metal surfaces by variable low-temperature scanning tunnelling microscopy.
In combination with molecular dynamics calculations we achieve a detailed understanding of the stability of these structures.?Atomic
nanostructures in homoepitaxial metallic systems are thermodynamically only metastable. Two-dimensional islands on Ag(110)
decay above a threshold temperature of T
l=175 K. Caused by the anisotropy of the surface, distinct decay behaviours exist above and below a critical temperature of
T
c=220 K. Calculations based on effective medium potentials of the underlying rate limiting atomic processes allow us to identify
the one-dimensional decay below T
c as well as the two-dimensional decay above T
c.?In contrast to atoms, the intermolecular electrostatic interaction of polar molecules leads to thermodynamically stable
structures. On the reconstructed Au(111) surface, the pseudo-chiral 1-nitronaphthalin forms two-dimensional supermolecular
clusters consisting predominantly of ten molecules. Comparison of images with submolecular resolution to local density calculations
elucidates the thermodynamical stability as well as the internal structure of the decamers.
Received: 25 March 1999 / Accepted: 17 August 1999 / Published online: 6 October 1999 相似文献
6.
We report on the frequency doubling of Q-switchedNd:YAG and Nd:YAlO3 lasers emitting at 946 and 930 nm, respectively (4F3/2 to 4I9/2 transition). The neodymium-doped laser host crystals were excited with a flashlamp-pumped Cr:LiSAF laser operating in a free-running
mode. Blue-light pulses were obtained at both 473 nm (9 mJ, 25 ns FWHM) and 465 nm (4.4 mJ, 35 ns FWHM) by using a potassium
niobate crystal as an extra-cavity frequency doubler. The second-harmonic generation conversion efficiencies reached 53% and
31%, respectively.
Received: 23 June 1999 / Revised version: 8 August 1999 / Published online: 3 November 1999 相似文献
7.
S. Gloor V. Romano W. Lüthy H.P. Weber V.V. Kononenko S.M. Pimenov V.I. Konov A.V. Khomich 《Applied Physics A: Materials Science & Processing》2000,70(5):547-550
Two-dimensional antireflective periodical microstructures for the IR range are fabricated on the surface of CVD diamond films.
These structures are created using an ArF excimer laser (λ=193 nm) and a direct writing scheme consisting of a beam collimator
and a microscope objective to focus the beam onto the sample. Two different arrays are investigated. One has a spacing of
3 μm and is produced with single shots and the other one has a spacing of 4 μm and is produced with three shots per spot.
The hole depth and shape are measured with an atomic force microscope (AFM). The optical transmittance and the scattering
properties of the structure at 10.6 μm are reported for a CO2 laser beam. With a spectrometer further transmission measurements in the range of 5 to 20 μm are performed.
Received: 16 September 1999 / Accepted: 11 October 1999 / Published online: 24 March 2000 相似文献
8.
The He-Ar-Cu+ IR laser operates in a hollow-cathode discharge, typically in a mixture of helium with a few-% Ar. The population inversion
of the Cu+ ion levels, responsible for laser action, is attributed to asymmetric charge transfer between He+ ions and sputtered Cu atoms. The Ar gas is added to promote sputtering of the Cu cathode. In this paper, a hybrid modeling
network consisting of several different models for the various plasma species present in a He-Ar-Cu hollow-cathode discharge
is applied to investigate the effect of Ar concentration in the gas mixture on the discharge behavior, and to find the optimum
He/Ar gas ratio for laser operation. It is found that the densities of electrons, Ar+ ions, Arm
* metastable atoms, sputtered Cu atoms and Cu+ ions increase upon the addition of more Ar gas, whereas the densities of He+ ions, He2
+ ions and Hem
* metastable atoms drop considerably. The product of the calculated Cu atom and He+ ion densities, which determines the production rate of the upper laser levels, and hence probably also the laser output power,
is found to reach a maximum around 1–5 % Ar addition. This calculation result is compared to experimental measurements, and
reasonable agreement has been reached.
Received: 14 October 2002 /
Revised version: 28 November 2002 / Published online: 19 March 2003
RID="*"
ID="*"Corresponding author. Fax: +32-3/820-23-76, E-mail: annemie.bogaerts@ua.ac.be 相似文献
9.
We propose a novel technique of sub-Doppler spectroscopy using a thin vapor cell. Optical pumping in a thin cell transfers
atoms with small velocity components to a specific quantum state. The resultant velocity distribution appears as a sub-Doppler
structure in the absorption spectrum of a probe light. A single laser beam from a laser diode is split into two paths: one
beam optically pumps Cs atoms on the D2 line, and the other probes the absorption on the same line from a perpendicular direction. Observed hyperfine-resolved spectra
and their parameter dependence are analyzed on the basis of rate equations.
Received: 16 January 2002 / Revised version: 11 February 2002 / Published online: 24 April 2002 相似文献
10.
F. Beinhorn J. Ihlemann K. Luther J. Troe 《Applied Physics A: Materials Science & Processing》1999,68(6):709-713
Micro-lenses with well-defined optical parameters are generated on polymethylmethacrylate (PMMA) substrates doped with diphenyltriazene
(DPT) by controlled use of a swelling effect generated under conditions of subablative excimer laser illumination. The surface
profiles depend on the laser spot size and energy density. A sensitively balanced combination of matrix softening, substrate
volume expansion due to photochemical nitrogen release, and surface tension is responsible for the final shape of the lenses.
Complete arrays of identical lenses with 15 μm diameters and a focal length of 30 μm are produced by irradiation of (0.25 wt. %)
DPT-PMMA with a single laser pulse at a wavelength of 308 nm and a fluence of 3 J/cm2. It is shown experimentally and theoretically that appropriate volume expansion is possible without introducing internal
light scattering due to the formation of small bubbles.
Received: 7 April 1999 / Accepted: 8 April 1999 / Published online: 5 May 1999 相似文献
11.
A new regime of chemical oxygen-iodine laser (COIL), high-pressure subsonic mode operation, was demonstrated using a jet-type
singlet oxygen generator (SOG). The laser output power of 342 W with chemical efficiency of 20.9% was obtained at the Cl2 flow rate of 18 mmol/s and the operating pressure of 6.4 Torr in the laser cavity. The specific energy was 3.1 J/l which
was four times higher than our supersonic device, and was comparable to the highest value for the supersonic regime. The experimental
results were in good agreement with the numerical simulation results.
Received: 26 February 1999 / Revised version: 13 July 1999 / Published online: 30 November 1999 相似文献
12.
Adiabatic focusing of cold atoms in a blue-detuned laser standing wave is analyzed. It is shown that using repulsive light
forces that push atoms towards dark regions and thus minimizes heating, cold atoms can be adiabatically compressed by more
than an order of magnitude to yield background-free sub-10-nm (rms) spots. The optimal parameters for the atomic lens and
the maximal compression ratio are predicted using an analytic model and found to be in agreement with the exact results of
our Monte Carlo simulations. A combined adiabatic-coherent scheme is proposed and shown to yield 8.8 nm spot size even for
a thermal atomic beam.
Received: 1 October 1999 / Revised version: 13 December 1999 / Published online: 5 April 2000 相似文献
13.
We have theoretically and experimentally investigated the focusing properties of a detuned pulsed standing wave onto a beam
of neutral atoms. In close analogy to the continuous-wave situation the dipole force leads to a periodic focusing of atoms
with a period of λ/2, provided an adiabatic condition is fulfilled. Pulsed laser light is conveniently converted to short
wavelengths and hence offers advantages in the application of atom lithography with elements of technological interest having
blue or UV resonance lines.
Received: 6 October 1999 / Revised version: 3 February 2000 / Published online: 5 April 2000 相似文献
14.
M. Neeb R. Klingeler P.S. Bechthold G. Kann I. Wirth S. Eisebitt W. Eberhardt 《Applied Physics A: Materials Science & Processing》2001,72(3):289-293
Mass spectra of fullerenes doped with transition and rare earth metals (Sc, Y, La, Ce, Gd) reveal a variety of singly and
doubly doped metallofullerenes. Characteristic oscillations of the relative mass intensities of the La- and Y-metallofullerenes
suggest the existence of two different isomers of the corresponding doubly doped fullerenes. The yield of the plasma-generated
clusters is sufficient to be used for an in situ deposition of mass-selected metallofullerenes onto a surface. In particular,
endohedral fullerenes with 60 or less atoms are accessible for deposition by means of a laser vaporization cluster source.
Scanning tunneling microscopy has been used to image Ce@C60 and La@C60 on highly oriented pyrolytic graphite.
Received: 24 May 2000 / Accepted: 6 November 2000 / Published online: 9 February 2001 相似文献
15.
C. Affolderbach A. Nagel S. Knappe C. Jung D. Wiedenmann R. Wynands 《Applied physics. B, Lasers and optics》2000,70(3):407-413
We have evaluated the suitability of a vertical-cavity surface-emitting laser diode (VCSEL) for spectroscopic applications.
Despite its low output power it is possible to observe narrow resonances in a saturated absorption spectroscopy experiment
on the cesium D
2 transition at 852 nm, limited in width by the laser linewidth of several tens of MHz. High modulation efficiency of the VCSEL
allows us to create modulation sidebands at 9.2 GHz frequency via direct modulation of the laser injection current. Using
the carrier and either one of the sidebands coherent population trapping (CPT) resonances in a buffered cesium vapor can be
prepared with linewidths below 130 Hz. With this very compact setup we have studied the dependence of CPT resonance position
and linewidth as a function of optical detuning and find evidence of the influence of the excited state hyperfine structure.
Received: 30 April 1999 / Revised version: 25 June 1999 / Published online: 30 November 1999 相似文献
16.
Narrow bandwidth operation of high-power broad-area diode laser using cascaded phase-conjugate injection locking 总被引:1,自引:0,他引:1
H. Horiuchi T. Shimura T. Omatsu O. Matoba K. Kuroda 《Applied physics. B, Lasers and optics》1999,68(5):1021-1025
A broad-area laser is injection-locked by another broad-area laser that is also injection-locked by a single-mode diode laser.
Two double-phase conjugate mirrors of photorefractive BaTaO3 are used to couple the master laser beams to the first slave laser, and the first slave laser output to the second slave
laser. One of the double-phase conjugate mirrors is built up with the beams from two broad-area lasers. Two slave lasers are
oscillating in single longitudinal mode at 808.5 nm and the spectral width is the same as that of the master laser. Final
single-mode output power from the second slave broad-area laser is 840 mW, which is limited by the power of the injection
beam. This work verifies the possibility of the multi-stage cascaded injection locking of high-power diode lasers with phase-conjugate
injection.
Received: 18 November 1998 / Revised version: 29 January 1999 / Published online: 7 April 1999 相似文献
17.
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
18.
L. Feenstra O.B. Hoekstra P.J.M. Peters W.J. Witteman 《Applied physics. B, Lasers and optics》2000,70(2):231-235
An X-ray preionised ArF and KrF excimer laser has been studied with three different spiker-sustainer excitation circuits.
We observed large differences in the laser performance, when the preionisation delay timing was varied on a nanosecond timescale.
The behaviour of both lasers was found to be equivalent. The observations can be understood by considering the effect of the
discharge excitation technique on the preionisation process. An excitation mode with a prepulse well above the steady-state
voltage VSS with a subsequent reversed overshoot voltage for initiating the discharge, in combination with a well-timed preionisation
pulse is found to give the best results. Optimum output energies of 50 mJ with ArF and 175 mJ with KrF were obtained from
an active volume of 60×1.5×1.2 cm in the so-called swing mode, with the preionisation applied 60 ns before the discharge breakdown.
Received: 23 February 1999 / Revised version: 4 June 1999 / Published online: 16 September 1999 相似文献
19.
T. Tsuboi 《Applied physics. B, Lasers and optics》1999,69(1):81-83
A stable, free-running LiF:F3
− and LiF:F2
− color center laser oscillation is achieved at room temperature by pumping with the 930-nm laser radiation. The LiF:F3
− laser radiation has a peak at 1100 nm and shifts from the peak wavelength of the F3
− luminescence band because of the absorption of the F3
− luminescence by the F2
− center, which co-exists with the F3
− center.
Received: 2 March 1999 / Revised version: 16 March 1999 / Published online: 12 May 1999 相似文献
20.
F. Kokai M. Taniwaki M. Ishihara Y. Koga 《Applied Physics A: Materials Science & Processing》2002,74(4):533-536
We deposited amorphous thin films of boron carbide by pulsed laser deposition using a B4C target at room temperature. As the laser fluence increased from 1 to 3 J/cm2, the number of 0.25–5 μm particulates embedded in the films decreased, and the B/C atomic ratio of the films increased from
1.8 to 3.2. The arrival of melt droplets, atoms, and small molecular species depending on laser fluence appeared to be involved
in the film formation. In addition, with increasing fluence the nanoindentation hardness of the films increased from 14 to
32 GPa. We believe that the dominant factor in the observed increase in the films’ hardness is the arrival of highly energetic
ions and atoms that results in the formation of denser films.
Received: 23 March 2001 / Accepted: 1 July 2001 / Published online: 2 October 2001 相似文献