共查询到20条相似文献,搜索用时 15 毫秒
1.
S. Borri P. Cancio P. De Natale G. Giusfredi D. Mazzotti F. Tamassia 《Applied physics. B, Lasers and optics》2003,76(4):473-477
We analyzed the spectroscopic performance of a difference-frequency source that utilizes a 5-W Yb-fiber amplifier for the
“signal” radiation in order to increase the “idler” power generated around 4.3 μm. The amplifier is seeded by a monolithic-cavity
Nd:YAG laser at 1064 nm. The intensity noise spectral density of the “idler” radiation was characterized. Cavity-enhanced
saturated-absorption spectroscopy was also performed to test the frequency resolution. In particular, we observed the Lamb-dip
spectrum of the ro-vibrational (0000-0001)R(0)transition of 17O12C16O in natural abundance. To our knowledge, this is the first observation of that transition by the Lamb-dip technique.
Received: 19 December 2002 / Revised version: 3 February 2003 / Published online: 16 April 2003
RID="*"
ID="*"Corresponding author. Fax: +39-055/4572-451, E-mail: mazzotti@inoa.it 相似文献
2.
X. Liu Q. Lu P. Liu M. Zhao Z. Wang M. Ying F. Li L. Qin 《Applied Physics A: Materials Science & Processing》2003,76(2):273-275
Range distributions for bismuth ions implanted in AgGaSe2 in the energy range 80–300 keV were investigated by using 2.1-MeV He2+ Rutherford backscattering spectrometry (RBS). A convolution calculation method was used to extract the true distributions
of bismuth from the measured RBS spectra. The range distribution parameters, Rp and ΔRp, were obtained and compared with those obtained from Monte Carlo simulation. The experimental Rp values agree with the Monte Carlo simulation values very well, but the experimental ΔRp values are systematically larger than those from the theoretical simulation.
Received: 28 January 2002 / Accepted: 11 April 2002 / Published online: 10 September 2002
RID="*"
ID="*"Corresponding author. Fax: +86-531/856-5167, E-mail: xdliu@sdu.edu.cn 相似文献
3.
The efficiencies of direct lidars operating at 355, 532, 1064 and 1540-nm radiation wavelengths for early forest fire detection
were compared. For each wavelength, the range for reliable smoke-plume detection was estimated on the basis of a computer
simulation plume using a one-dimensional “top-hat” gas dynamic model for the calculation of the backscattering and extinction-coefficient
profiles within the plume. The agreement between the predicted signal-to-noise ratio (SNR) and experimental results for 532
and 1064-nm wavelength radiation is good. The decrease of the signal-to-noise ratio with distance is maximum for 355 nm and
minimum for 1064 nm. At 1540 nm, the decay of SNR with distance is slightly faster, but the SNR is higher than for other wavelengths,
leading to the highest detection efficiency for the same energy of the probing laser pulse. For a burning rate of 2 kg/s and
a laser beam divergence of 2.5 mr, the maximum distance for reliable detection varies between 6 and 12 km, depending on the
wavelength.
Received: 15 May 2002 / Revised version: 13 September 2002 / Published online: 22 January 2003
RID="*"
ID="*"Corresponding author. Fax: +351-21/841-8120, E-mail: rui.vilar@ist.utl.pt 相似文献
4.
A.G. Berezin O.V. Ershov A.I. Nadezhdinskii 《Applied physics. B, Lasers and optics》2002,75(2-3):203-214
The goal of the present paper was to develop an experimental technique to detect trace concentrations of complex molecules
in the atmosphere using near-IR diode lasers. Ethanol and propane were chosen as model species. New optical, hardware, instrument-operation-mode
and data-processing approaches for detection of trace complex molecules were developed. Different physical processes limiting
the sensitivity of trace molecule detection were considered and solutions were developed to reduce the influence of these
mechanisms on instrument operation. An absorption sensitivity of αmin=2.5×10-5 for 4.5 ms measurement time was achieved, which is comparable with the sensitivity of “small” molecule detection. The first
results utilizing this technique for in-field monitoring of trace complex molecules are presented.
Received: 25 April 2002 / Revised version: 29 May 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +7-095/135-8281, E-mail: anber@nsc.gpi.ru 相似文献
5.
A model is derived linking microdroplet emission of a liquid-metal ion source (LMIS) to the actual current–voltage characteristic
and operating temperature. All parameters were experimentally investigated using an indium LMIS, confirming the relationships
found. The model allows for the first time the optimisation of a LMIS for low droplet emission at high emission currents.
This is very important for application as a thruster, which has been developed at ARC Seibersdorf research. It can be also
used to extrapolate droplet emission values along the current–voltage characteristic.
Received: 29 January 2002 / Accepted: 7 October 2002 / Published online: 17 December 2002
RID="*"
ID="*"Corresponding author. Fax: +43-50550/3366, E-mail: martin.tajmar@arcs.ac.at 相似文献
6.
The influence of the surface roughness of polypropylene on the contact angle hysteresis is investigated by means of ethylene
glycol drops in order to estimate the true Young’s equilibrium contact angle. A new relationship between the contact angle
hysteresis and Wenzel’s contact angle is derived. In addition, the determination of Wenzel’s roughness factor by means of
scanning force microscopy opens an alternative way to obtaining Young’s equilibrium contact angle without any surface manipulation.
The experimental results presented verify this new approach.
Received: 2 September 2002 / Accepted: 2 September 2002 / Published online: 5 March 2003
RID="*"
ID="*"Corresponding author. Fax: +49-3328/352-452, E-mail: helmut.kamusewitz@gkss.de 相似文献
7.
F.C. Fonseca G.F. Goya R.F. Jardim N.L.V. Carreño E. Longo E.R. Leite R. Muccillo 《Applied Physics A: Materials Science & Processing》2003,76(4):621-623
Ni nanoparticles embedded in an amorphous SiO2 matrix were produced by a modified sol–gel method. This method resulted in nanocomposites with a controlled size distribution
and good dispersion of the metallic particles. The particle-size distributions were found to have an average radius of ∼3 nm,
as inferred from transmission electron microscopy, X-ray-diffraction analysis, and magnetic measurements. Magnetic characterizations
revealed that samples exhibit superparamagnetic behavior above the blocking temperature TB, 20 K≤TB≤40 K, and absence of a shift along the field axis on hysteresis loops measured at T≤TB, indicating that the metallic nanoparticles are also free from an oxide layer.
Received: 7 October 2002 / Accepted: 9 October 2002 / Published online: 8 January 2003
RID="*"
ID="*"Corresponding author. Fax: +55-11/3091-6984, E-mail: rjardim@if.usp.br 相似文献
8.
J.C. Bermudez Gutierrez M.J. Damzen V.J. Pinto-Robledo A.V. Kir’yanov J.J. Soto-Bernal 《Applied physics. B, Lasers and optics》2003,76(1):13-16
The analysis of compact CW diode-side-pumped grazing-incidence-geometry Nd:YVO4 laser designs is presented. An output power of 5 W (λ=1064 nm) was produced at 17 W of diode pump (conversion efficiency
of 30%) in single transverse TEM00 mode operation at high laser beam quality (Mx
2≈1.05 and My
2≈1.01). The resonator geometry was analyzed by applying generalized 4×4 matrix modeling of the spatial mode size, including
the impact on the laser operation of cavity astigmatism and a thermal lens in the laser slab. The simplicity and compactness
of the laser cavities allow their use for technological applications.
Received: 31 July 2002 / Published online: 22 January 2003
RID="*"
ID="*"Corresponding author. Fax: +44-20/7594-7744, E-mail: m.damzen@ic.ac.uk 相似文献
9.
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
10.
We study the forced aspiration of small ( mm) and large ( cm) liquid drops, deposited on prewetted porous membranes, and pumped mechanically with a constant current J. Two kinds of membranes are used where the pores are i) disconnected, cylindrical and calibrated or ii) interconnected “sponge-like”.
Whatever the size of the drops and the intensity J of the current, two suction regimes are observed versus time: 1) a “locked” regime, when the drop is pinned, with a dynamic contact angle decreasing from advancing () to finite receding () contact angle; 2) an “unlocked” regime, where the contour line recedes with a constant contact angle closed to . In both regimes, the shape of the drop remains quasistatic, during the suction process, i.e. a spherical cap for small drops and a flat “gravity pancake” for large ones.
Received 19 January 2000 相似文献
11.
12.
From laser-induced line narrowing to electro- magnetically induced transparency: closed system analysis 总被引:1,自引:0,他引:1
The laser-induced line-narrowing effect, discovered more than thirty years ago, can also be applied to recent studies in high
resolution spectroscopy based on electromagnetically induced transparency. In this paper we first present a general form of
the transmission width of electromagnetically induced transparency in a homogeneously broadened medium. We then analyze a
Doppler broadened medium by using a lorentzian function as the atomic velocity distribution. The dependence of the transmission
linewidth on the driving field intensity is discussed and compared to the laser-induced line-narrowing effect. This dependence
can be characterized by a parameter which can be regarded as “the degree of optical pumping.”
Received: 17 December 2001 / Published online: 15 January 2003
RID="*"
ID="*"Corresponding author. E-mail: hwang.Lee@jpl.nasa.gov
RID="**"
ID="**"Present address: Jet Propulsion Laboratory, MS 126-347, California Institute of Technology, Pasadena, CA 91109, USA 相似文献
13.
J.-M. Liu N. Chong H.L.W. Chan K.H. Wong C.L. Choy 《Applied Physics A: Materials Science & Processing》2003,76(1):93-96
Epitaxial (001) aluminum nitride (AlN) thin films on (111) Si substrates are prepared using pulsed-laser deposition. The epitaxial
structure of the as-prepared thin films is characterized by checking the X-ray-diffraction θ-2 θ scan and pole-figure, using
scanning electron microscopy, infrared radiation (IR) spectroscopy and Raman spectroscopy. The surface acoustic-wave resonance
at 345 MHz for a 1.5 μm thick AlN film on a (111) Si substrate is observed using an inter-digital electrode.
Received: 18 September 2001 / Accepted: 29 January 2002 / Published online: 3 June 2002
RID="*"
ID="*"Corresponding author. Fax: +86-25/359-5535, E-mail: liujm@nju.edu.cn 相似文献
14.
V.C. Selvaraju S. Asokan V. Srinivasan 《Applied Physics A: Materials Science & Processing》2003,77(1):149-153
The I–V characteristics of bulk As40Te60-xSex and As35Te65-xSex glasses have been studied with a current sweep of 0–18 mA-0, over a wide range of compositions (4≤x≤22). All the glasses
studied showed a threshold electrical switching behaviour. The number of switching cycles withstood by the samples has been
found to depend on the ON-state current. It is seen that the switching voltages increase with increase in selenium content.
Further, the switching voltages are found to be almost independent of the thickness of the sample (d), in the range 0.18–0.3 mm.
Also, the switching voltages and the number of switching cycles withstood by the samples are found to decrease with temperature.
Received: 6 November 2002 / Accepted: 8 November 2002 / Published online: 29 January 2003
RID="*"
ID="*"Corresponding author. Fax: +91-80/360-0135, E-mail: sasokan@isu.iisc.ernet.in 相似文献
15.
A reliable and efficient method based on a geometrical optical approach is presented to model the propagation of ultrashort
pulses in optical systems. It is shown that the commonly used method to determine the group delay of the spectral components
of a pulse from their geometrical optical path lengths is only correct for aberration-free optical systems. In the case of
systems with angular dispersion and imaging errors, a correction to the path values obtained from ray-tracing calculations
must be applied, since for specific systems neglect of the correction causes significant errors. A technique for performing
this correction is presented. Two optical arrangements used for the generation and detection of tunable THz radiation by the
femtosecond tilted-pulse-front excitation technique are analyzed to demonstrate the indispensability of the correction.
Received: 29 July 2002 / Revised version: 22 October 2002 / Published online: 29 January 2003
RID="*"
ID="*"Corresponding author. Fax: +36-72/501-571, E-mail: kozma@fizika.ttk.pte.hu 相似文献
16.
T.J. Kulp S.E. Bisson R.P. Bambha T.A. Reichardt U.-B. Goers K.W. Aniolek D.A.V. Kliner B.A. Richman K.M. Armstrong R. Sommers R. Schmitt P.E. Powers O. Levi T. Pinguet M. Fejer J.P. Koplow L. Goldberg T.G. McRae 《Applied physics. B, Lasers and optics》2002,75(2-3):317-327
Quasi-phase-matched (QPM) materials allow the generation of spectroscopically useful infrared radiation in an efficient and
broadly tunable format. Here, we describe several applications of QPM-based light sources to remote and local chemical sensing.
The remote systems are gas imagers that employ a fiber-pumped continuous-wave optical parametric oscillator or a microlaser-pumped,
diode-seeded optical parametric amplifier as the illumination source. Technology described for local sensing includes a cavity
ring down spectrometer that employs a novel optical parametric generator–amplifier to achieve ≥350 cm-1 of contiguous tuning and a long-wave infrared light source based on QPM GaAs. In each case the use of QPM materials in conjunction
with effective pump sources instills simplicity and ruggedness into the sensing systems.
Received: 15 April 2002 / Revised version: 6 June 2002 / Published online: 12 September 2002
RID="*"
ID="*"Corresponding author. Fax: +1-925/294-2595, E-mail: tjkulp@sandia.gov
RID="**"
ID="**"Present address: Corning Inc., Corning, NY 14831, USA
RID="*"
ID="*"Present address: Corning Inc., Corning, NY 14831, USA
RID="**"
ID="**"Present address: Blue Leaf Networks, Sunnyvale, CA 94086, USA
RID="***"
ID="***"Present address: Sandia National Laboratories, Albuquerque, NM 87185, USA 相似文献
17.
The results of statistical simulation of the spatiotemporal structure of the multiply scattered component of lidar returns
by the Monte Carlo method are discussed for the case of monostatic sensing geometry. The spatial characteristics of the region
of the medium where occurs the last scattering of photon before arriving at the reciever. This region of the medium is called
the instantaneous brightness body of multiply scattered radiation. It is demonstrated that the instantaneous brightness body
of multiply scattered radiation that propagates toward the receiver may occupy a large volume that does not necessarily coincide
with the region of formation of the singly scattered component. The main factors influencing the spatial and brightness characteristics
of this volume source are established. The effect of scattering order on the spatiotemporal structure of lidar returns is
analyzed for the case of sensing of aerosol haze and advective and radiative fogs with optical thickness 2<τ<8.
Received: 2 August 2001 / Revised version: 7 January 2002 / Published online: 25 September 2002
RID="*"
ID="*"Corresponding author. Fax: +7-38/2225-8026, E-mail: belov@iao.ru 相似文献
18.
V.G. Savitski N.N. Posnov P.V. Prokoshin A.M. Malyarevich K.V. Yumashev M.I. Demchuk A.A. Lipovskii 《Applied physics. B, Lasers and optics》2002,75(8):841-846
Passive mode locking and saturable absorber Q-switching of neodymium lasers at 1.3 μm with PbS-doped phosphate glasses are
demonstrated. Q-switched pulses of 120 ns (0.1 μJ) in duration (energy) and the average output power of 3 mW from a quasi-cw
diode-pumped Nd3+:KGW laser and ultrashort pulses of a maximum of 250 μJ in energy and 150 ps in duration from a Nd3+:YAP laser were obtained. The bleaching decay rate of the samples was found to increase with the Quantum Dot’s size decreasing
due to the enhancement of quantum confinement effects for smaller dots and stronger overlapping of the electron and trap state
wave functions.
Received: 23 January 2002 / Revised version: 2 April 2002 / Published online: 20 December 2002
RID="*"
ID="*"Corresponding author. Fax: +375-17/232-6286, E-mail: savitski@eudoramail.com 相似文献
19.
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
20.
Z. Siwy D. Dobrev R. Neumann C. Trautmann K. Voss 《Applied Physics A: Materials Science & Processing》2003,76(5):781-785
For the preparation of a single asymmetrically shaped nanopore in a polyimide membrane, Kapton foils were irradiated with
single heavy ions and subsequently etched from one side in sodium hypochlorite (NaOCl). The other side of the membrane was
protected from etching by a stopping medium containing a reducing agent for hypochlorite ions (OCl-). The resulting conical nanopore rectified ion current and exhibited a stable ion-current flow.
Received: 23 May 2002 / Accepted: 2 September 2002 / Published online: 15 January 2003
RID="*"
ID="*"Corresponding author. Fax: +49-6159/712-179, E-mail: Z.Siwy@gsi.de 相似文献