共查询到20条相似文献,搜索用时 31 毫秒
1.
G. Hadinger M. Aubert-Frécon G. Hadinger 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(1):63-72
Approximate expressions for the eigenvalue of a three-term recurrence relation with a general form describing various physical
problems are proposed. Their range of availability is examined by comparison with exact values for two different problems:
the bound and continuum states of monoelectronic diatomic ions and the Schr?dinger equation describing molecular alignment
in intense laser fields. For each case, very good predictions have been obtained, which may be useful as initial values in
iterative procedures for deriving exact solutions.
Received: 30 January 1998 / Received in final form: 10 April 1998 / Accepted: 25 May 1998 相似文献
2.
3.
Y.F. Lu S.M. Huang C.H.A. Huan X.F. Luo 《Applied Physics A: Materials Science & Processing》1999,68(6):647-651
It is demonstrated that a liquid hydrocarbon precursor, cyclohexane, is appropriate for laser-induced carbon deposition. Amorphous
hydrogenated carbon films (a-C:H) were deposited by KrF excimer laser irradiation of single-crystal silicon surface immersed
under cyclohexane. The technique is simple and easy to operate. IR absorption spectra of the deposited films confirmed the
presence of carbon in the diamond phase. Raman and XPS studies showed diamond-like character of the deposited films. Moreover,
these two studies provided strong evidence that laser fluence played an important role in the formation of DLC bondings and
the quality of the deposited films.
Received: 15 September 1998 / Accepted: 5 January 1999 / Published online: 5 May 1999 相似文献
4.
E. Roissé V. Couderc A. Barthélémy F. Louradour 《Applied physics. B, Lasers and optics》1999,69(2):89-91
We report the first diode-pumped solid-state laser operating in cw-mode-locked regime and simultaneously achieving intracavity
frequency-tripling. This laser provide UV picosecond pulses (λ=355 nm) of 10 ps duration with 0.5 mW average power at 150 MHz
repetition rate. A different set of adjustments gave rise to a Q-switched mode-locked regime. Trains of hundred UV pulses
of 60 ps duration and 4 W peak power were produced in this latter case at 50 kHz repetition rate.
Received: 12 October 1998 / Revised version: 12 December 1998 / Published online: 26 May 1999 相似文献
5.
F. Mougel F. Augé G. Aka A. Kahn-Harari D. Vivien F. Balembois P. Georges A. Brun 《Applied physics. B, Lasers and optics》1998,67(5):533-535
3+ :Ca4GdO(BO3)3 (Nd:GdCOB). 21 mW of green cw laser emission for an absorbed pump power of 820 mW were achieved under laser diode-pumping.
64 mW of green cw laser output were obtained with 1 W of absorbed pump power under titanium-sapphire pumping. Its availability
in large-size crystals with good optical quality makes Nd:GdCOB a true challenger to the best SFD laser crystal reported so
far: Nd:YAl3(BO3)4 (Nd:YAB or NYAB).
Received: 2 March 1998/Revised version: 20 May 1998 相似文献
6.
J. Jersch F. Demming I. Fedotov K. Dickmann 《Applied Physics A: Materials Science & Processing》1999,68(6):637-641
Time-resolved dependence of the transient current through a ns laser pulse illuminated scanning tunneling microscope (STM)
tip/sample gap in tunneling mode and out of tunneling range is presented. A self-designed fast STM-preamplifier (bandwidth
35 MHz) allows one to resolve the fine structure of the transient signal as well as the observation of some effects that are
undetectable by using conventional low-band preamplifiers. The dependence of the threshold laser pulse intensity, which corresponds
to the beginning of electron emission from tip (in non-tunneling mode), as a function of the tip/sample distance was investigated.
At tip/sample distances from tunnel contact up to approximately 1 μm a linear dependence is found. This behavior is in good
agreement with the theory for field enhancement in a STM tip/sample system. In tunneling mode a ns (fast component) as well
as a μs (slow component) current response was found as a result of the laser pulse illumination. These data suggest the tip
bending to be an important factor in clarifying the thermal/mechanical mechanism of laser-assisted surface nanomodification.
Received: 4 May 1998 / Accepted: 29 January 1999 / Published online: 28 April 1999 相似文献
7.
S. Gnutzmann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(1):109-123
A simple model of a bad-cavity laser is presented based on Haken's master equation for N pumped two-level atoms in a cavity. Via adiabatic elimination of fast variables the whole photon statistics is solved analytically near threshold. It is shown that
the second order coherence function g
(2)
(0) has a very different behavior near threshold for a bad-cavity laser compared to a good-cavity laser. The power spectrum
illustrates nicely the different time scales involved in the dynamics.
Received: 13 November 1998 / Revised: 19 May 1998 / Accepted: 6 July 1998 相似文献
8.
Y. Kuga M. Hirasawa T. Seto K. Okuyama K. Takeuchi 《Applied Physics A: Materials Science & Processing》1999,68(1):75-80
5 nanoparticles equipped with an in situ size-monitoring system, a LPDMA (low-pressure differential mobility analyzer), was
developed to experimentally investigate the nanoparticle growth mechanism. The concentration of photoproduced UF5 molecules was controlled by changing three factors: (I) the concentration of the feed UF6 gas, (II) the laser pulse energy of the irradiation, and (III) the repetition rate of the laser pulses. The dependence of
the volumetric average diameter of the photoproduced particles on the UF5 nascent concentration in all three cases was found to be very similar. The result strongly suggests that the reactor functions
as a mixed-flow reactor under a complete mixing condition. The particle size measured by the LPDMA was found to be in the
range of 6 to 11 nm, and it was approximately proportional to the power 0.3 of the initial concentration of photoproduced
UF5 molecules.
Received: 11 May 1998/Accepted: 15 September 1998 相似文献
9.
It is well known that saturating gain media can give rise to superluminal pulse propagation velocity. In most mode-locked
lasers the effect is unmeasurably small and has not yet been directly demonstrated. We present experiments on the initial
transient of an erbium fiber laser that show a dynamic shift in the propagation velocity to a value larger than the medium’s
linear group velocity as the pulse builds up.
Received: 14 December 1998 / Revised version: 21 May 1999 / Published online: 25 August 1999 相似文献
10.
High-speed machining of glass materials by laser-induced plasma-assisted ablation using a 532-nm laser 总被引:2,自引:0,他引:2
J. Zhang K. Sugioka K. Midorikawa 《Applied Physics A: Materials Science & Processing》1998,67(4):499-501
+ :YAG laser (532 nm). The plasma generated from a silver (Ag) target by the laser irradiation effectively assists in ablation
of the fused quartz substrate by the same laser beam, although the laser beam is transparent to the substrate. A grating with
a cross-sectional shape like a square-wave (period ≈ 20 μm) is achieved using the mask projection technique. The ablation
rate reaches several tens nm/pulse. In addition, LIPAA is applied to high-speed hole drilling (700 μm in diameter) of fused-quartz
(0.5 mm thick) and Pyrex glass (0.5 mm thick).
Received: 25 May 1998/Accepted: 19 June 1998 相似文献
11.
Characteristics of thermo-mechanical laser ablation process are investigated using an original numerical model. In contrast
with previous models, it is based on a microscopic physical model of the micro-explosion process, which combines thermodynamic
behavior of tissue water with elastic response of the solid tissue components. Diffusion of dissipated heat is treated in
one dimension, and the amount of thermal damage is assessed using the Arrhenius model of the protein denaturation kinetics.
Influence of the pulse fluence and duration on temperature profile development, ablation threshold, and depth of thermal damage
is analyzed for the case of Er:YAG laser irradiation of human skin. Influence of mechanical properties on the ablation threshold
of soft tissue is predicted theoretically for the first time. In addition, feasibility of deep tissue coagulation with a repetitively
pulsed Er:YAG laser is indicated from the model.
Received: 9 July 1998 / Revised version: 26 February 1999 / Published online: 26 May 1999 相似文献
12.
E. Roissé F. Louradour O. Guy V. Couderc A. Barthélémy 《Applied physics. B, Lasers and optics》1999,69(1):25-27
We propose enhanced frequency-doubling inside an external ring-cavity using type II nonlinear crystal. A KTP type II twin-crystal
device is implemented for compensation of both walk-off and phase-shift between ordinary and extraordinary fundamental waves.
Starting from an 850 mW diode-pumped actively mode-locked Nd:YAG laser at 1.064 μm with 100 MHz repetition rate and 25 ps
pulse duration, we performed 54% harmonic conversion efficiency in the green.
Received: 31 August 1998 / Revised version: 10 February 1999 / Published online: 19 May 1999 相似文献
13.
Excited state absorption and stimulated emission of Nd3+ in crystals. Part 2: YVO4, GdVO4, and Sr5(PO4)3F 总被引:1,自引:0,他引:1
L. Fornasiero S. Kück T. Jensen G. Huber B.H.T. Chai 《Applied physics. B, Lasers and optics》1998,67(5):549-553
3+ ion in the crystals YVO4, GdVO4, and Sr5(PO4)3F. The measurements were performed in the spectral region of the main laser transitions 4F3/2→4I9/2, 4F3/2→4I11/2, and 4F3/2→4I13/2by a continuous wave pump and probe technique. The calibrated gain and ESA spectra are presented and possible implications
of ESA on the laser performance are estimated. It is shown that ESA can be a small loss factor to the laser emission near
1060 nm but does considerably diminish the effective emission cross sections near 1340 nm especially in Nd:YVO4 and Nd:GdVO4.
Received: 29 January 1998/Revised version: 8 May 1998 相似文献
14.
V. Drinek H. Niino J. Pola A. Yabe 《Applied Physics A: Materials Science & Processing》2001,73(4):527-530
An organosilicon compound, hexamethylcyclotrisilazane (HMCTS), was photolyzed in a solid film at 84 K with an ArF excimer
laser. A polymeric film was prepared as a result of polymerization and/or crosslinking using a reactive species such as 1-(methylsilyl)methanimine,
generated by photolysis. At room temperature in air, the film changed into a polymer having siloxane units. However, fragments
generated by laser irradiation of HMCTS in the frozen film made a similar polymer film having a siloxane structure on a PVA
film in air. The polymeric film with siloxane units prepared by the cryogenic laser ablation method displayed hydrophobic
properties.
Received: 23 May 2001 / Accepted: 30 May 2001 / Published online: 30 August 2001 相似文献
15.
Laser polishing of diamond plates 总被引:5,自引:0,他引:5
S.M. Pimenov V.V. Kononenko V.G. Ralchenko V.I. Konov S. Gloor W. Lüthy H.P. Weber A.V. Khomich 《Applied Physics A: Materials Science & Processing》1999,69(1):81-88
Results are reported on laser polishing of 150–400-μm-thick free-standing diamond films with either a copper vapor laser (510 nm
wavelength) or an ArF excimer laser (193 nm wavelength). Studies were focused on three particular goals. First, we aimed at
a choice of optimum conditions for laser polishing of thick diamond films. It was shown that the laser polishing conditions
and the resulting surface roughness were controlled by varying the angle of incidence of a scanning laser beam and by polishing
time. Second, the laser ablation technique was applied to remove a defective layer from the “substrate” side of the diamond
plates in order to reduce optical losses due to absorption in this layer. Third, the structure of the laser-graphitized diamond
surface was studied using UV, visible, and IR optical spectroscopy techniques in the course of the “step-by-step” oxidative
removal of the graphitic layer with increasing temperature of the oxidation in ambient air. Once the graphitic layer was removed,
the optical transmission in the UV-visible-IR spectral range of the diamond films polished under optimum conditions was measured
and compared with the optical transmission of the mechanically polished diamond films. It was shown that the optical quality
(in the long-wave infrared region) of the laser-polished diamond plates was sufficient to reach the transmittance value very
close to the theoretical limit.
Received: 20 October 1998 / Accepted: 8 March 1999 / Published online: 5 May 1999 相似文献
16.
The laser performance of the Nd:KGW crystal has been studied in a master oscillator and power amplifier configuration (MOPA).
Several crystals from two different producers were investigated for the oscillator and the amplifier. A maximum single-pass
gain of 25 was observed in free-running and Q-switched mode. We obtained a maximum output amplified energy of 400 mJ at 30 Hz
(with a pulse duration of 10 to 30 ns) with a divergence less than 3 mrad. We also studied the limitations of this configuration
due to the very high gain of the Nd:KGW crystal.
Received: 21 September 1998 / Revised version: 10 January 1999 / Published online: 19 May 1999 相似文献
17.
2 and two diode lasers as pump sources are presented. A single-mode Fabry–Pérot-type tunable diode laser (TDL) and an external-cavity
diode laser (ECL) were combined to generate radiation in the mid-infrared region near 7.2 μm. With a TDL at a wavelength of
approximately 1290 nm and an ECL emitting between 1504 and 1589 nm it was possible to carry out spectroscopic experiments
concerning SO2 at five different phasematching points between 1350 and 1400 cm-1 by fixing the wavelength of one pump laser and tuning the wavelength of the other. With an input power of 8 mW for the single-mode
Fabry–Pérot-type diode laser and 6 mW for the external-cavity laser an output power of about 10 nW was generated. Using the
tuning capabilities of the external-cavity laser a spectral region up to 5 cm-1 could be covered within one scan. Measurements of SO2 absorption lines at low pressure demonstrate the high-resolution features of the spectrometer. Moreover, these data provide
new direct experimental phasematching data for the rarely investigated spectral region at 7.2 μm.
Received: 27 October 1997/Revised version: 8 May 1998 相似文献
18.
A general expression for the cooperative diffusion constant of weakly charged gels is derived as a function of the thermodynamic
parameters such as polyelectrolyte concentration, salt concentration, ionic strength, and the degree of crosslinking. In the
low concentration range it decreases with the monomer concentration.
Received: 30 January 1998 / Revised: 4 May 1998 / Accepted: 6 May 1998 相似文献
19.
Q-switching of a diode-pumped Nd:YVO4 laser using a quadrupole electro-optic deflector 总被引:3,自引:0,他引:3
G.J. Friel R.S. Conroy A.J. Kemp B.D. Sinclair J.M. Ley 《Applied physics. B, Lasers and optics》1998,67(2):267-270
4 laser and this produced 1.5-ns pulses of 7 kW peak power at a repetition rate of 20 kHz.
Received: 11 May 1998 相似文献
20.
Broadly tunable difference-frequency generation (DFG) in AgGaS2 was achieved by mixing dual-wavelength oscillating pulses from an electronically tuned Ti:sapphire laser with a two-frequency-driven
acousto-optic device. Continuous tuning from 6.5 to 8.5 μm was achieved by simultaneous dual-wavelength-tuned DFG without
crystal rotation. In the dual-pulse oscillation, the shorter and longer wavelength pulses were tuned from 700 to 775 nm and
from 763 to 880 nm, respectively, while keeping the phase-matching relationship for DFG. When crystal rotation was adopted,
however, the tunable output range was extended from 5.3 to 12 μm by tuning the longer wavelength pump pulse, while the shorter
wavelength pulse was fixed.
Received: 18 November 1998 / Revised version: 5 February 1999 / Published online: 26 May 1999 相似文献