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1.
T. Brixner 《Applied physics. B, Lasers and optics》2003,76(5):531-540
The usage of Poincaré phase space for the representation of polarization-shaped femtosecond laser pulses is discussed. In
these types of light fields the polarization state (i.e. ellipticity and orientation) changes as a function of time within
a single laser pulse. Such deliberate variation can be achieved by frequency-domain femtosecond pulse shaping in which two
polarization components are manipulated individually. Here it is shown how these light pulses can be represented as temporal
trajectories through the ellipticity-orientation (Poincaré) phase space, whereas conventional light (either continuous-wave
or pulsed) is determined by only one specific Poincaré location. General properties of parametric Poincaré trajectories are
discussed, and their relation to experimentally accessible pulse-manipulation parameters (i.e. amplitudes and phases) determined.
Specifically, it is shown how the maximum rate by which a given polarization state can be turned into a different one (at
significant intensity levels) is limited by the spectral laser bandwidth. Apart from their direct usage in polarization-shaped
pulse representation, Poincaré trajectories also form the basis for intuitive quasi-three-dimensional renderings of the electric
field profile. There, the temporal evolution of polarization, intensity, and chirp is directly apparent in a single illustration.
Received: 10 December 2002 / Published online: 24 April 2003
RID="*"
ID="*"Corresponding author. Fax: +49-931/888-4906, E-mail: brixner@physik.uni-wuerzburg.de 相似文献
2.
A 50 cm silver coated hollow fiber with inner diameter of 250 μm and filled with argon has been used to compress optical pulses
from a Ti:sapphire laser at 800 nm. Input pulses with energy of 250 μJ and duration of 110 fs were used and compressed pulses
with energy of 220 μJ and duration of 20 fs were generated by using a prism compressor. Numerical and experimental results
are compared. There is good agreement between the measured beam diameters of the hollow-fiber output pulse and the calculated
values obtained from propagation of the HE11 mode into free space. For comparison, a similar uncoated fused-silica hollow fiber was also used to obtain 20 fs compressed
pulses with an energy of 190 μJ.
Received: 7 September 2002 / Published online: 26 March 2003
RID="*"
ID="*"Corresponding author. Fax: +1-780/492-1811, E-mail: mohebbi@ee.ualberta.ca 相似文献
3.
We report on a passively Q-switched diode-pumped Nd:YVO4 laser polarized along the a axis (corresponding to the smallest value of emission cross section at 1064 nm), generating 157-μJ
pulses with 6.0-ns time duration (>20 kW peak power) and 3.6 W of average power at 1064 nm with good beam quality (M2<1.4). The selection of the polarization was performed by a novel technique relying on the birefringence of the laser crystal
and on the misalignment sensitivity of the resonator.
Received: 30 September 2002 /
Revised version: 22 November 2002 / Published online: 19 March 2003
RID="*"
ID="*"Corresponding author. Fax: +39-382/422583, E-mail: agnesi@ele.unipv.it 相似文献
4.
G. Zhang H. Wang Y. Yu F. Xiong G. Tang W. Chen 《Applied physics. B, Lasers and optics》2003,76(6):677-681
All-optical switching and beam deflection of 2-(2′-hydroxyphenyl) benzoxazole (HBO) in three species of solvent (cyclohexane, ethanol and dimethyl sulfoxide) have been investigated
by using third-harmonic generation (355 nm) of a mode-locked Nd:YAG laser as a pump beam and a continuous-wave He-Ne laser
(632.8 nm) as a probe beam. The nonlinear refractive indices of HBO in different solvents are determined by using the Z-scan
technique. The optical switching and beam-deflection effects are due to the change of the refractive index of HBO under the
pump beam. Through the study of the absorption spectra and the fluorescence spectra of HBO in different solvents, we conclude
that the principal reason for the change of the refractive index of HBO is not the thermal effect because of absorption of
the pump beam, but the excited-state intramolecular proton-transfer (ESIPT) effect of HBO under the pump beam. As the ESIPT
process is very fast, HBO might be an excellent material for high-speed optical switching.
Received: 28 October 2002 / Revised version: 18 March 2003 / Published online: 2 June 2003
RID="*"
ID="*"Corresponding author. Fax: +86-22/2350-1242, E-mail: zhanggl@nankai.edu.cn 相似文献
5.
A high-repetition-rate eye-safe optical parametric oscillator (OPO), using a non-critically phase-matched KTP crystal intracavity
pumped by an acousto-optically (AO) Q-switchedNd:YVO4 laser, is experimentally demonstrated. It is found that the average OPO signal power at 1573 nm can be efficiently increased
by increasing the pulse repetition rate. Moreover, the intracavity OPO process effectively shortens the pulse width so that
it is in the range 5∼8 ns for pulse repetition rates of 10 to 80 kHz. As a result of the relatively short pulse, the peak
power at 1573 nm is higher than 2 kW at a pulse repetition rate of 80 kHz.
Received: 10 July 2002 / Published online: 26 February 2003
RID="*"
ID="*"Corresponding author. Fax: +886-35/729-134, E-mail: yfchen@cc.nctu.edu.tw 相似文献
6.
7.
The generation of programmable complex femtosecond pulses in the mid infrared (3–10 μm) with high precision is reported. Designed
pulse shapes in the near infrared (1–1.6 μm) are transferred to the mid infrared via difference-frequency mixing with a second
infrared pulse spectrally narrowed in a zero-dispersion compressor. In particular, pulse sequences with variable relative
phases have been obtained. The control of the pulse properties is achieved purely electronically, allowing for implementation
into a feedback loop.
Received: 12 December 2003 / Published online: 3 April 2003
RID="*"
ID="*"Corresponding author. Fax: +49-89/32905-200, E-mail: mcm@mpq.mpg.de 相似文献
8.
Three-dimensional reversible laser micromachining of polymer materials based on two-photon photochromism is demonstrated.
Unamplified 60-fs, 0.5-nJ pulses of 790-nm Ti:sapphire laser radiation are used to induce a refractive-index change in a polymethyl
methacrylate (PMMA) sample doped with spiropyran molecules through a two-photon absorption process. Waveguides are written
in the bulk of spiropyran-doped PMMA samples by scanning these samples with respect to a tightly focused Ti:sapphire laser
beam. Laser-induced fluorescence is used for on-line monitoring of the laser-micromachining process. The structures written
in photochromic samples can be erased and reconfigured due to the reversibility of the photochromic effect.
Received: 23 April 2003 / Published online: 6 June 2003
RID="*"
ID="*"Corresponding author. Fax: +7-095/939-51-74, E-mail: zheltikov@top.phys.msu.su 相似文献
9.
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
10.
Sub-nanosecond microchip laser with intracavity Raman conversion 总被引:3,自引:0,他引:3
A.A. Demidovich P.A. Apanasevich L.E. Batay A.S. Grabtchikov A.N. Kuzmin V.A. Lisinetskii V.A. Orlovich O.V. Kuzmin V.L. Hait W. Kiefer M.B. Danailov 《Applied physics. B, Lasers and optics》2003,76(5):509-514
Efficient sub-nanosecond pulse operation of microchip lasers with intracavity Raman conversion and pulse compression is presented
for the first time. The microchip lasers were composed of Nd:LSB or Nd:YAG laser crystals, Cr4+:YAG saturable absorber, and Ba(NO3)2 Raman medium. The pulse duration obtained at the Stokes wavelength (1196 nm) was as short as 118 ps. Optical conversion efficiency
of laser-diode pump power to the Stokes power of 8% was reached. Pulse energy and peak power of Stokes emission were 1.2 μJ
and 5.4 kW, correspondingly. Numerical calculations are in good agreement with obtained experimental results.
Received: 20 December 2002 / Revised version: 6 March 2003 / Published online: 5 May 2003
RID="*"
ID="*"Corresponding author. Fax: +1-716/645-6945, E-mail: ankuzmin@acsu.buffalo.edu
RID="**"
ID="**"Present address: University at Buffalo, SUNY, The Institute for Lasers, Photonics, and Biophotonics, 458 NSC, Buffalo,
NY 14 260-3000, USA 相似文献
11.
S. Pereira J.E. Sipe M.A. Bader S. Soria G. Marowsky 《Applied physics. B, Lasers and optics》2002,75(6-7):635-640
We theoretically demonstrate the feasibility of using a grating-waveguide structure (GWS) as a loss-tolerant, narrow-band
reflector in the UV. We simulate device operation using a Green-function technique. Our numerical simulations indicate that
a GWS with a 25-nm grating can be used as a 95% reflector for 157-nm light, even in the presence of intensity absorptions
of 50 cm-1.
Received: 23 July 2002 / Published online: 22 November 2002
RID="*"
ID="*"Corresponding author. Fax: +49-551/5035-99, E-mail: mbader@llg.gwdg.de 相似文献
12.
D. Lognoli G. Cecchi I. Mochi L. Pantani V. Raimondi R. Chiari T. Johansson P. Weibring H. Edner S. Svanberg 《Applied physics. B, Lasers and optics》2003,76(4):457-465
Extensive fluorescence multispectral imaging of the cathedral and baptistery of Parma, Italy, is reported and discussed. In
particular, the first fluorescence imaging data from protection-treated stony materials were recorded. Fluorescence spectra
were taken with a mobile lidar system scanning the monument surfaces with a frequency-tripled Nd:YAG laser beam from a distance
of about 80 m. For each pixel of the area investigated, a high-spectral-resolution spectrum in the full visible range was
acquired. The principal-component analysis technique was used to obtain thematic maps that outlined areas subject to protective
treatment and biological growth, and other features, such as different types of stones and decoration pigments.
Received: 24 July 2002 / Revised version: 16 January 2003 / Published online: 3 April 2003
RID="*"
ID="*"Corresponding author. Fax: +39-055/410-893, E-mail: g.cecchi@ifac.cnr.it 相似文献
13.
Pliński E.F. Witkowski J.S. Majewski B.W. Abramski K.M. 《Applied physics. B, Lasers and optics》2003,76(4):375-382
The behaviour of a rf-excited waveguide CO2 laser in the pulse regime is studied experimentally. The specific time sections of the pulse have been defined and described
in detail. The output pulse evolution versus input power, pressure of the laser mixture, output coupling, repetition frequency
and pulse width has been investigated. The spectral content of the pulse has been analysed. A model explaining the effect
of laser tuning during the pulse duration is given. The ultrahigh pulse (UHP), defined as the pulse for which the bulge effect
occurs, is predicted.
Received: 22 October 2002 / Revised version: 13 January 2003 / Published online: 26 March 2003
RID="*"
ID="*"Corresponding author. Fax: +48-71/3203-189, E-mail: eda@zr.ita.pwr.wroc.pl 相似文献
14.
A deconvolution filtering model of multiple scattering in ground-based single field of view (SFOV) LIDAR returns is described.
It is based on time series deconvolution techniques. The contribution of multiply scattered photons in SFOV LIDAR returns
can be numerically modeled by processing LIDAR signals without additional information about aerosol properties and measurement
geometry. Deconvolution results are in good agreement with those performed by Monte Carlo calculations, showing that the significance
of multiply scattered photons is strongly correlated with aerosol concentration. It is found that, for ground-based LIDAR,
the contribution of multiply scattered photons to LIDAR signals is typically below 5% in a clear urban atmosphere, and up
to 14% in a very dirty urban atmosphere in Hong Kong during winter seasons.
Received: 8 October 2002 / Revised version: 29 January 2003 / Published online: 22 May 2003
RID="*"
ID="*"Corresponding author. Fax: +81-298/51-8229, E-mail: gao@proteo.gr.jp
RID="**"
ID="**"Present address: Preteomics Lab., Amakubo 1-16-1, Tsukuba 305-0005, Japan 相似文献
15.
T. Lippert M. Hauer C.R. Phipps A. Wokaun 《Applied Physics A: Materials Science & Processing》2003,77(2):259-264
The ablation characteristics of various polymers were studied at low and high fluences for an irradiation wavelength of 308 nm.
The polymers can be divided into three groups, i.e. polymers containing triazene groups, designed ester groups, and reference
polymers, such as polyimide. The polymers containing the photochemically most active group (triazene) exhibit the lowest thresholds
of ablation (as low as 25 mJ cm-2) and the highest etch rates (e.g. 250 nm/pulse at 100 mJ cm-2), followed by the designed polyesters and then polyimide. Neither the linear nor the effective absorption coefficients have
a clear influence on the ablation characteristics. The different behavior of polyimide might be explained by a pronounced
thermal part in the ablation mechanism. The laser-induced decomposition of the designed polymers was studied by nanosecond
interferometry and shadowgraphy. The etching of the triazene polymer starts and ends with the laser pulse, indicating photochemical
ablation. Shadowgraphy reveals mainly gaseous products and a pronounced shockwave in air. The designed polymers were tested
for an application as the polymer fuel in laser plasma thrusters.
Received: 21 October 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +41-56/3104-412, E-mail: thomas.lippert@psi.ch 相似文献
16.
Laser action was generated in dye-doped sol–gel glass waveguides and in liquid solutions by crossing two beams from a frequency-doubled
neodymium:YAG laser. The angle between the polarization directions of the two beams was varied continuously from 90. The case
of 0° corresponded to pure intensity modulation. As the angle increased, the degree of intensity modulation decreased, resulting
in the decline and finally the demise of the laser output. At 90°, corresponding to pure polarization modulation, distributed
feedback laser action with narrow line-width output was again observed when the pump energy was increased three-fold. The
laser output also showed different polarization characteristics when the feedback mechanism was changed from intensity modulation
to polarization modulation.
Received: 13 February 2003 / Revised version: 3 April 2003 / Published online: 22 May 2003
RID="*"
ID="*"Corresponding author. Fax: 852/2603-5204, E-mail: dlo@sun1.phy.cuhk.edu.hk 相似文献
17.
Mode splitting was observed when a He-Ne laser beam was reflected through a prism-coupled liquid-crystal slab waveguide under
an applied electric field. The splitting manifests itself as the imposed voltage reaches a critical level, and diminishes
when the voltage increases above a critical high value. If the applied voltage increases even further, mode splitting vanishes,
attributing to the result that almost all the directors of the liquid crystal turn upright to the surface. The multi-layer
matrix simulation can satisfactorily account for this phenomenon by exploiting the property of the anisotropic optical birefringence
of a liquid crystal under applied voltages.
Received: 2 December 2002 / Revised version: 24 January 2003 / Published online: 23 May 2003
RID="*"
ID="*"Corresponding author. Fax: +886/3572-3052, E-mail: jtlue@phys.nthu.edu.tw 相似文献
18.
Interference patterns generated by a regular lattice of SiO2 microspheres on a transparent support are used for the surface patterning of polyimide (PI) foils. Using 248 nm excimer-laser
radiation, thousands to millions of holes with a full width at half maximum (FWHM) of 160±40 nm can be generated with a single
laser pulse.
Received: 1 March 2002 / Accepted: 4 March 2002 / Published online: 10 September 2002
RID="*"
ID="*"Corresponding author. Fax: +43-732/2468-9242, E-mail: dieter.baeuerle@jku.at 相似文献
19.
T.V. Andersen J. Thogersen S.R. Keiding J.J. Larsen 《Applied physics. B, Lasers and optics》2003,76(6):639-644
We demonstrate intracavity frequency doubling of a standard femtosecond Ti:sapphire oscillator. The cavity is extended with
a pair of focusing mirrors and a 0.5-mm-thick BBO crystal. We achieve a repetition rate of 50 MHz and simultaneously generate
22 mW of 55-fs pulses at 810 nm and 200 mW of 73-fs pulses at 405 nm, which corresponds to 4 nJ per pulse. We create a total
of 330-mW, 405-nm light when pumping the Ti:sapphire crystal with 5.7 W from an Ar-ion laser, corresponding to a conversion
efficiency of 5.7%. No saturation is found, which implies that higher outputs can be achieved with higher pump rates. Preliminary
results from the use of blue pulses as pump in an optical parametric amplifier seeded by pulses from a photonic crystal fiber
are presented.
Received: 27 January 2003 / Revised version: 27 March 2003 / Published online: 12 May 2003
RID="*"
ID="*"Corresponding author. Fax: +45-861/96199, E-mail: tva@chem.au.dk 相似文献
20.
D. Ashkenasi G. Müller A. Rosenfeld R. Stoian I.V. Hertel N.M. Bulgakova E.E.B. Campbell 《Applied Physics A: Materials Science & Processing》2003,77(2):223-228
Experimental investigations using femtosecond and picosecond laser pulses at 800 nm illuminate the distinctions between the
dynamics and nature of ultrafast processing of dielectrics compared with semiconductors and metals. Dielectric materials are
strongly charged at the surface on the sub-ps time scale and undergo an impulsive Coulomb explosion prior to thermal ablation.
Provided the laser pulse width remains in the ps or sub-ps time domain, this effect can be exploited for processing. In the
case of thermal ablation alone, the high localization of energy accompanied by ultrafast laser micro-structuring is of great
advantage also for high quality processing of thin metallic or semiconducting layers, in which the surface charge is effectively
quenched.
Received: 17 January 2003 / Accepted: 8 February 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +49-30/670-53-500, E-mail: d.ashkenasi@lmtb.dt
RID="**"
ID="**"Present address: LMTB GmbH, Berlin, Fabeckstr. 60–62, D-14195 Berlin, Germany 相似文献