共查询到20条相似文献,搜索用时 296 毫秒
1.
J.S. Gibb G. Hancock A. Hutchinson R. Peverall G.A.D. Ritchie 《Applied physics. B, Lasers and optics》2003,76(1):97-105
A simple technique is demonstrated for the accurate determination of pressure-induced line shifts of water in air. High- and
low-pressure water samples are simultaneously probed on selected overtone transitions at 1.32 μm using a current-modulated
distributed-feedback diode laser and harmonic detection. The resultant profiles yield an average line shift of -293±30 MHz/atm
for the 3,3,0 (002)2,2,1 (000)transition at 227251 GHz and -134±7 MHz/atm for the 3,2,1 (002)2,1,2 (000) transition at 227027 GHz.
Comparisons are made between first- and second-harmonic detection, and wavelength- and frequency-modulation regimes. The effect
of modulation broadening on the returned line shifts is quantified.
Received: 12 August 2002 / Revised version: 21 October 2002 / Published online: 8 January 2003
RID="*"
ID="*"Corresponding author. Fax: +44-01865/275410, E-mail: gus.hancock@chemistry.ox.ac.uk 相似文献
2.
C. Moreau E. Therssen P. Desgroux J.F. Pauwels A. Chapput M. Barj 《Applied physics. B, Lasers and optics》2003,76(5):597-602
The potential of Laser Induced Fluorescence detection of the CH radical using C–X (0–0) excitation is investigated in a sooting
methane/air diffusion flame at atmospheric pressure. Fluorescence is detected using the very narrow (<0.4 nm) Q-branch of
the C–X (0–0) band, which enables the measurement of CH in sooting flames without interference from PAH fluorescence and soot
emissions. Absolute concentrations are obtained using Cavity Ring Down Spectroscopy. 1D CH profiles in the sooting zone are
recorded using a CCD camera with an excellent signal-to-noise ratio. The C–X (0–0) excitation associated with Q-branch detection
is shown to be three times more efficient than the B–X scheme.
Received: 4 March 2002 / Revised version: 5 November 2002 / Published online: 5 May 2003
RID="*"
ID="*"Corresponding author. Fax: +33-3/2033-6463, E-mail: eric.therssen@univ-lille1.fr 相似文献
3.
S.K. Lam D. Lo C.E. Zheng C.L. Yuan C. Shangguan T.L. Yang I.V. Kochetov 《Applied physics. B, Lasers and optics》2002,75(6-7):723-730
Optical and electrical properties of a high-pressure discharge of pure xenon and xenon-helium and xenon-neon mixtures are
studied experimentally. Uniform discharge at total gas pressure as high as 10 atm is achieved in xenon-lean mixtures. Vacuum
ultraviolet emissions due to the first and second continua of Xe2
* are examined spectroscopically. The vibrational relaxation rate constant kHe of Xe2
* by helium is determined to be of the order of 10-11 cm3 s-1 from spectroscopic data. Laser oscillation for the 172-nm band was attempted without success. Discharge instability at high
gas pressures is considered to the cause of the unsuccessful laser experiments. Some issues related to discharge instability
in a high-pressure rare-gas discharge are discussed.
Received: 1 October 2001 / Revised version: 11 June 2002 / Published online: 25 October 2002
RID="*"
ID="*"Corresponding author. Fax: +852-2603/5204, E-mail: dlo@phy.mhk.edu.hk 相似文献
4.
Z.J. Li X.L. Chen L. Dai H.J. Li H.W. Liu H.J. Gao Y.P. Xu 《Applied Physics A: Materials Science & Processing》2003,76(1):115-118
A new form of GaN nanomaterial (nanotweezers) has been obtained by chemical vapor deposition on an etched cubic MgO (100)
plane. The nanotweezers consist of a bottom rod and two arms. The bottom rods have diameters of about 100–150 nm and lengths
of about 200–500 nm, on which two arms grow out. The bottoms of the arms are about 40–70 nm and the tops are about 15–30 nm
in diameter, and 0.8–1.5 μm in length. X-ray and electron diffractions indicate the nanotweezers are zinc blende gallium nitride.
We infer that the fabrication of the GaN nanotweezers is associated with small convex hillocks on the surface of the etched
cubic MgO (100) single-crystal substrates and that the nanotweezers grow by a growth mechanism that is similar to vapor-phase
heteroepitaxy.
Received: 23 April 2002 / Accepted: 25 April 2002 / Published online: 10 September 2002
RID="*"
ID="*"Corresponding author. Fax: +86-10/8264-9531, E-mail: xlchen@aphy.iphy.ac.cn 相似文献
5.
G. Tsilimis J. Kutzner H. Zacharias 《Applied Physics A: Materials Science & Processing》2003,76(5):743-749
An extreme ultraviolet (EUV) laser light source based on high-harmonic generation is presented. Coherent radiation in the
photon energy range hν=20–120 eV is produced in the conversion media argon, neon and helium. High-harmonic radiation in the
energy range 20–50 eV is applied to investigate photoemission spectra of Pt (111) and CO/Pt (111). In the photoemission spectra
of the clean surface, new secondary electron emission structures are found which influence the cross section analysis of the
CO states. When taking these Pt resonances into consideration, the 4σ and 5σ CO shape resonances are found at photon energies
of 37 eV and 28 eV, respectively. Additionally, a resonance at hν=31 eV is also observed for the CO 1π state, in contrast
to formerly published experimental data. Experimental and theoretical data suggest that this resonance is not connected to
the well-known shape resonances in the σ-channel. Based on theoretical approaches, it is identified as an autoionization resonance.
Received: 8 April 2002 / Accepted: 22 May 2002 / Published online: 22 November 2002
RID="*"
ID="*"Corresponding author. Fax: +49-251/833-3604, E-mail: kutzner@uni-muenster.de 相似文献
6.
Düsterer S. Schwoerer H. Ziegler W. Salzmann D. Sauerbrey R. 《Applied physics. B, Lasers and optics》2003,76(1):17-21
The influence of prepulses on the conversion efficiency (CE) of laser radiation into 13 nm extreme ultraviolet (EUV) radiation,
resulting from lithium-like oxygen ions from O20 μm water droplets, was investigated. The laser pulse durations in the experiment
ranged from 200 fs to 120 ps. Applying prepulses preceding the main pulse at various delays of up to 11 ns, it was shown that
the CE increases differently for each measured pulse duration. The strongest dependence on the introduction of a prepulse
was observed for 2 ps laser pulses with a 20 mJ laser pulse energy. The EUV CE was improved by a factor of 15 by the introduction
of a prepulse. Calculations on the atomic physics of oxygen ions and simulations of the laser–plasma interaction revealed
the influence of the prepulse on the EUV yield.
Received: 25 October 2002 / Published online: 22 January 2003
RID="*"
ID="*"Corresponding author. Fax: +49-3641/947-202, E-mail: duesterer@ioq.uni-jena.de 相似文献
7.
The use of mid-infrared polarization spectroscopy (PS) for the detection of CO2 has been demonstrated. The P(13) and P(14) resonances of the (0 00 0)→(1 00 1) transition of CO2 were probed using a single-mode optical parametric generator system to produce a high-intensity laser beam at approximately
2.7 μm. The experiments were performed in an atmospheric pressure CO2 jet and also in a sub-atmospheric pressure gas cell. The experimental results were compared with the results of the time-dependent
density-matrix equations using direct numerical integration. The Zeeman-state structure of the upper and lower energy levels
was included in the multi-state formulation of the density-matrix equations. Fifty-eight Zeeman states and two bath levels
were included in the numerical analysis of the P(14) transition. The measured and calculated PS line shapes were in good agreement,
and the absolute experimental signal level agreed with the theoretical calculation to within a factor of five.
Received: 20 March 2002 / Revised version: 16 August 2002 / Published online: 11 December 2002
RID="*"
ID="*"Present address: Innovative Scientific Solutions Inc., 2766 Indian Ripple Road, Dayton, OH 45 440, USA
RID="**"
ID="**"Corresponding author. Fax: +1-765/494-0539, E-mail: Lucht@purdue.edu
RID="***"
ID="***"Present address: School of Mechanical Engineering, Purdue University, W. Lafayette, IN 47807-2040 USA 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.
Efficient room-temperature operation of 4
F
3/24
I
9/2 transitions in diode-end-pumped Nd:YAG lasers at 946 nm and 938.5 nm is reported. 7.0-W continuous-wave output power at 946 nm
and 3.9 W at 938.5 nm have been obtained. An analytical model has been developed for the quasi-three-level laser including
the influence of energy-transfer upconversion. Frequency doubling of these transitions in periodically poled KTP generated
blue light at 473 nm and 469 nm. Both single-pass extra-cavity as well as intracavity schemes have been investigated.
Received: 31 July 2002 / Published online: 5 February 2003
RID="*"
ID="*"Corresponding author. Fax: +46-8/750-5430, E-mail: stefan.bjurshagen@acreo.se 相似文献
10.
Results are given for thermal tuning and modulation of a 1556-nm distributed feedback fibre laser by resistive heating of
a thin silver film chemically deposited on the fibre. Without reaching the limits of performance, linear tuning is demonstrated
at a rate of 1.72 pm/mW up to about 200 pm, and a peak-to-peak modulation of 100 MHz up to modulation frequencies of 60 Hz.
The heat flow is analyzed, and the coated fibre is characterized in terms of the static and dynamic wavelength response to
the applied electric power. The performance of the scheme is tested by recording part of the ν1+ν3 combination band spectrum of 13C2H2 with thermal modulation and scanning of the fibre laser.
Received: 12 March 2002 / Revised version: 24 June 2002 / Published online: 25 September 2002
RID="*"
ID="*"Corresponding author. Fax: +45/4593-1137, E-mail: sus@dfm.dtu.dk 相似文献
11.
J. Guéna E. Jahier M. Lintz A. Papoyan S. Sanguinetti M.A. Bouchiat 《Applied physics. B, Lasers and optics》2002,75(6-7):739-743
We observe charge multiplication of photoemitted electrons in cylindrical alumina cells, containing cesium vapor, submitted
to a longitudinal electric field and to intense laser pulses. We present several diagnoses allowing us to attribute this charge
multiplication to efficient secondary electron emission (SEE) from the accelerated photoelectrons colliding with the inner
wall at grazing incidence. Machining millimeter-size triangular grooves on the initially smooth inner wall, so as to prevent
grazing incidence, is shown to be efficient in reducing SEE. The atomic signal characteristic of the space charge accumulated
close to the anode is found to be reduced by more than one order of magnitude. This result is of important significance, not
only for our parity-violation experiment in cesium vapor, but also for experiments and techniques involving SEE at grazing
incidence.
Laboratoire de l’Ecole Normale Supérieure associé au CNRS (UMR 8552) et à l’Université Pierre et Marie Curie.
Received: 25 June 2002 / Revised version: 11 September 2002 / Published online: 15 November 2002
RID="*"
ID="*"Present address: Institute for Physical Research, Ashtarak-2, 378 410 Armenia.
RID="**"
ID="**"Corresponding author. Fax: +33-1/4432-3434, E-mail:marianne@lkb.ens.fr 相似文献
12.
M.B. Pushkarsky M.E. Webber O. Baghdassarian L.R. Narasimhan C.K.N. Patel 《Applied physics. B, Lasers and optics》2002,75(2-3):391-396
An industrial trace-ammonia sensor based on photoacoustic spectroscopy and CO2 lasers has been developed for measuring ammonia with a 1σ detection limit of 220 parts-per-trillion (ppt) in an integration
time of 30 s. The instrument response time for measuring ammonia was 200 s, limited by adsorption effects due to the polar
nature of ammonia. The minimum detectable fractional absorbance was 2.0×10-7, and the minimum normalized detectable absorption coefficient for this system was 2.4×10-7 W cm-1/z. The 9R(30) transition of the CO2 laser at 9.22 μm with 2 W of output power was used to probe the strong sR(5,K) multiplet of ammonia at the same wavelength. This sensor was demonstrated with an optically multiplexed configuration
for simultaneous measurement in four cells.
Received: 3 April 2002 / Revised version: 31 May 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +1-310/458-0171, E-mail: webber@pranalytica.com 相似文献
13.
M. Yorozu J. Yang Y. Okada T. Yanagida F. Sakai S. Ito A. Endo 《Applied physics. B, Lasers and optics》2003,76(3):293-297
Polarization-dependent spatial beam profiles of femtosecond X-ray pulses generated by a laser Compton scheme were measured.
The X-ray pulses were generated by the interaction at an angle of 90° between 100-fs laser light and a 3-ps, 3π-mm mrad electron
beam. The polarization of the laser light was linear in two different directions, either parallel or perpendicular to the
electron beam axis. The measured profiles showed good agreement with theoretical results.
Received: 5 July 2002 / Revised version: 17 October 2002 / Published online: 5 February 2003
RID="*"
ID="*"Corresponding author. Fax: +81-424/684477, E-mail: msf_yorozu@shi.co.jp 相似文献
14.
B. Bakowski L. Corner G. Hancock R. Kotchie R. Peverall G.A.D. Ritchie 《Applied physics. B, Lasers and optics》2002,75(6-7):745-750
Cavity-enhanced absorption spectroscopy is explained in terms of the transmission function of a rapidly swept interferometer,
and the integrated transmission is shown to be proportional to the cavity ringdown time. The technique is demonstrated on
the b1Σg
+-X3Σg
- (1,0) band in molecular oxygen at 687 nm using a tunable diode laser and a relative-ly high-Q optical cavity (finesse ≈4000).
A detection limit of 3×10-8 cm-1 s1/2 is achieved for a 0.8 cm-1 scanning range.
Received: 24 June 2002 / Revised version: 5 August 2002 / Published online: 15 November 2002
RID="*"
ID="*"Corresponding author. Fax: +44-1865/275410, E-mail: peverall@physchem.ox.ac.uk 相似文献
15.
N. Navi H. Kim J.S. Horwitz H.D. Wu S.B. Qadri 《Applied Physics A: Materials Science & Processing》2003,76(5):841-846
The structural and the microwave dielectric properties of BaxSr(1-x)TiO3 films (BST) with x=0.5, 0.6 and 0.7, containing 1 mol % W have been investigated. The films were grown by pulsed-laser deposition
on MgO (001) substrates at a temperature of 720 °C in an oxygen pressure from 3 to 500 mTorr. The film structures were determined
by X-ray diffraction. The lattice parameters were fitted to a tetragonal distortion of a cubic lattice. The out-of-plane lattice
parameter (c) was calculated from the position of the (004) reflection. Using c, the in-plane lattice parameter, a, was calculated
from the position of the (024) and (224) reflections. A deviation in the calculated values for a, beyond the systematic error,
was found in the in-plane lattice parameter, suggesting an in-plane orthorhombic distortion (a, a’). Films with x=0.7 showed
a minimum in-plane distortion due to a better lattice match with the substrate. The ratio of the in-plane and out-of-plane
lattice parameters was calculated as a measure of the lattice distortion (a/c and a’/c). The dielectric properties of the
films deposited were measured at room temperature at 2 GHz using gap capacitors fabricated on top of the dielectric film.
For all Ba/Sr ratios investigated in the W-doped material, the dielectric Q (1/cosδ) was observed to be insensitive to the
oxygen deposition pressure. A peak in the change in the dielectric constant, as a function of an applied electric field (0–80 kV/cm),
was observed for films deposited in 50 mTorr of oxygen. The largest K-factor, K=(ε(0)-ε(V )/ε(0)×Q(0)), for films deposited
from a BST x=0.6 (1 mol % W-doped) target was observed in the film that had a minimum in-plane strain, where a∼a’ and c was
greater than a and a’.
Received: 4 July 2002 / Accepted: 5 July 2002 / Published online: 17 December 2002
RID="*"
ID="*"Permanent address: Nuclear Research Center–Negev, P.O. Box 9001 Beer-Sheva, Israel
RID="**"
ID="**"Corresponding author. Fax: +1-202/767-5301, E-mail: horwitz@ccsalpha3.nrl.navy.mil 相似文献
16.
A. Costela I. García-Moreno C. Gómez O. García R. Sastre 《Applied physics. B, Lasers and optics》2002,75(8):827-833
We report on the laser action of rhodamine 6G (Rh6G) incorporated into new hybrid organic–inorganic monolithic materials.
The synthesis of these materials proceeded via the simultaneous sol-gel process of the inorganic part (tetraethoxysilane or
tetramethoxysilane) and the free-radical polymerization of an organic monomer part (2-hydroxypropyl methacrylate, 2-hydroxyethyl
methacrylate and a 1:1 v/v copolymer of this monomer with methyl methacrylate). The wt. % proportion of the alkoxide was systematically
varied in each organic formulation, and the effect of each organic–inorganic composition on the lasing properties of Rh6G
was evaluated. The laser samples were transversely pumped and the influence on the laser action of dye concentration, pump
wavelength and pump repetition rate was analyzed. Lasing efficiencies of up 26% and good stabilities, with a 90% drop in the
initial laser output of up to 12000 pump pulses at 2.5 Hz, were obtained when the samples were pumped at 355 nm with 5.5 mJ/pulse
from the third harmonic of a Q-switched Nd:YAG laser.
Received: 31 July 2002 / Revised version: 14 October 2002 / Published online: 20 December 2002
RID="*"
ID="*"Corresponding author. Fax: +34-91/564-4853, E-mail: ogarcia@ctp.csic.es 相似文献
17.
P.E. Dyer S.M. Maswadi C.D. Walton 《Applied Physics A: Materials Science & Processing》2003,76(5):817-822
We report an investigation of the ablation of NaCl crystals at the 157-nm wavelength of the F2 laser where there is very strong excitonic absorption. Probe-beam deflection and etch-rate measurements show that the interaction
is characterised by a low ablation threshold (∼80 mJ cm-2) and a capability for controllable material removal at the nanometer level. Scanning electron microscopy of the exposed surfaces
show this to be microscopically smooth but with fine cracks present. It is demonstrated that micron-scale features can be
formed in NaCl using 157-nm laser ablation, a result attributed to the strongly localised optical and thermal nature of the
interaction. The results are discussed within the framework of a thermal vaporisation model.
Received: 29 May 2002 / Accepted: 17 July 2002 / Published online: 4 November 2002
RID="*"
ID="*"Corresponding author. Fax: +44-1482/465606, E-mail: p.e.dyer@hull.ac.uk 相似文献
18.
X. Zhu S. Lu H.L.W. Chan C.L. Choy K.H. Wong 《Applied Physics A: Materials Science & Processing》2003,76(2):225-229
Compositionally graded (Ba1-xSrx)TiO3 (BST) (x:0.0∼0.25) thin films were grown on Pt (111)/TiO2/SiO2/Si (100) substrates using layer-by-layer pulsed laser deposition in the temperature range 550–650 °C. Both downgraded (Ba/Sr
ratio varying from 100/0 at the bottom surface to 75/25 at the top surface) and upgraded (Ba/Sr ratio varying from 75/25 at
the bottom surface to 100/0 at the top surface) BST films were prepared. Their microstructures were systematically studied
by X-ray diffractometry and scanning electron microscopy. A grain morphology transition from large ‘rosettes’ (>0.30 μm) to
small compact grains (70–110 nm) was observed in the downgraded BST films as the deposition temperature was increased from
550 to 650 °C. No such grain morphology transition was detected in the upgraded BST films. Dielectric measurements with metal
electrodes revealed an enhanced dielectric behavior in the downgraded films. This enhancement is mainly attributed to the
large compressive stress field built up near the interface between the downgraded film and substrate. Furthermore, the BaTiO3 layer in the downgraded BST films not only serves as a bottom layer but also as an excellent seeding layer for enhancing
the crystallization of the subsequent film layers in the downgraded films.
Received: 10 December 2001 / Accepted: 12 March 2002 / Published online: 19 July 2002
RID="*"
ID="*"Corresponding author. Fax: 86-25/359-5535, E-mail: xhzhu@public1.ptt.js.cn 相似文献
19.
C. Dölle C. Reinhardt P. Simon B. Wellegehausen 《Applied physics. B, Lasers and optics》2002,75(6-7):629-634
. Investigations of the efficient generation of powerful coherent radiation at 82.8 nm by frequency tripling of short-pulse
KrF laser radiation are presented. Argon gas is selected as nonlinear medium due to the resonantly enhanced 3rd-order susceptibility
χ(3)(-3ω,ω,ω,ω). Pulse energies of 100 μJ at 82.8 nm have been measured for a pump pulse energy of 14 mJ. An upscaling to more
than 500 μJ is expected with available more powerful pump lasers. Features of this XUV source and possible applications are
discussed.
Received: 26 July 2002 / Published online: 15 November 2002
RID="*"
ID="*"Corresponding author. Fax: +49-511/7622211, E-mail: reinhardt@iqo.uni-hannover.de 相似文献
20.
The ohmic contact characteristics of Au/Pt/Ti on degenerated doped n-GaAs were evaluated. Structural and electrical properties
were studied by means of X-ray diffraction (XRD), Auger Energy Spectrum (AES) and a HP4145B parameter analyzer. The structural
analysis revealed a TiAs phase in the interface between metal multilayer and GaAs at higher annealing temperatures. Electrical
measurement showed a minimum ohmic contact resistance of 3×10-4 Ω cm2. The dominant current mechanism was found to be thermionic emission with a barrier height of Φb, of 0.09 V by comparing the experimental data with different theoretical models.
Received: 14 December 2001 / Accepted: 4 April 2002 / Published online: 22 November 2002
RID="*"
ID="*"Corresponding author. Fax: +86-21/6226-4397, E-mail: zhoujian999@163.net 相似文献