共查询到20条相似文献,搜索用时 406 毫秒
1.
M. Mürtz J.S. Wells L. Hollberg T. Zibrova N. Mackie 《Applied physics. B, Lasers and optics》1998,66(3):277-281
2 cryostat that permits placement of both the collimation optics and the extended-cavity elements within a vacuum chamber.
We have observed tuning of the laser frequency over a 1.44 THz (48 cm-1) range by rotation of the external grating. This result was obtained without anti-reflection coating of the laser output
facet.
Received: 8 July 1997/Revised version: 31 July 1997 相似文献
2.
A. Nayak G.L. Bhalla G.C. Trigunayat 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(3):319-323
Highly purified single crystals of cadmium iodide obtained through repeated zone refining have been subjected to laser beam
exposure (Argon ion laser), both for various time durations and to various beam intensities, and then subjected to band gap
determination by UV spectroscopy. The band gap has been found to decrease gradually with increase in the laser beam intensity,
whereas its variation with increase in time of exposure shows an unusual behaviour such that it initially falls sharply followed
by a gradual rise back to its original value. The results have been analysed and interpreted in terms of indirect band gap
character of the material and an unusual variation in phonon frequency. The interpretation is well supported by X-ray diffraction
and scanning electron microscopy (SEM) studies.
Received: 26 May 1997 / Revised: 6 August 1997 / Accepted: 15 September 1997 相似文献
3.
The absolute frequency of an iodine-stabilized He-Ne laser at 633 nm stabilized on the i (or a13) component of the 11-5 R(127) hyperfine transition of the 127I2 molecule is measured using a femtosecond optical comb generator and an iodine-stabilized Nd:YAG laser standard at 1064 nm.
We link the measured absolute frequency to the current internationally adopted value via frequency intercomparison between
JILA and the Bureau International des Poids et Mesures (BIPM), leading to the determination of the absolute frequency of the
BIPM-4 standard laser. The resulting absolute frequency fi(BIPM) of the BIPM-4 standard laser is fi(BIPM)=473612214711.9±2.0 kHz, which is 6.9 kHz higher than the value adopted by the Comité International des Poids et Mesures (CIPM)
in 1997.
Received: 29 May 2000 / Revised version: 13 September 2000 / Published online: 22 November 2000 相似文献
4.
Loesel F.H. Fischer J.P. Götz M.H. Horvath C. Juhasz T. Noack F. Suhm N. Bille J.F. 《Applied physics. B, Lasers and optics》1998,66(1):121-128
2 ; for 100 fs pulses from the same laser the experimental threshold was at 1.5 J/cm2. Histopathological examinations and scanning electron micrographs confirm the high quality of the excisions. No sign of significant
thermal damage was observed.
Received: 29 January 1997/Revised version: 14 July 1997 相似文献
5.
E. Arimondo F. Calderazzo F. Fuso C. Toffi 《Applied Physics A: Materials Science & Processing》1998,66(4):407-411
2 . The dependence of the ion production on the laser ablation parameters is investigated and the expansion dynamics of the
ablated species is studied through time and space resolved measurements of the ion yield. We discuss our observations on the
basis of reactions involving neutral and ionized carbon-based species.
Received: 11 March 1997/Accepted: 30 June 1997 相似文献
6.
E. Cormier P. Lambropoulos 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(1):15-20
We report on observable new features related to ionization of atoms by laser pulses of only few cycles and some intensity.
We show that for particular photo-electron energies, the angular distribution becomes asymmetric and that this asymmetry is
related to the initial phase of the field.
Received: 4 November 1997/Revised: 21 January 1998/Accepted: 23 February 1998 相似文献
7.
N. Naumov V. Petrovskiy E. Protsenko V. Yermachenko 《Applied physics. B, Lasers and optics》1997,65(4-5):589-593
4 gas laser with an intracavity absorbing cell is studied experimentally and theoretically at a modulation frequency approximately
equal to the intermode beat frequency. It is revealed that in the vicinity of the absorption-line centre the intensity of
every mode for certain system parameters displays resonance structures narrower than the homogeneous line width of the absorption
line. This occurs when the range of mode synchronization is near the absorption-line centre and its size is less than the
homogeneous width of the absorption line.
Received: 29 February 1996/Revised version: 4 February 1997 相似文献
8.
C. Vadla K. Niemax V. Horvatic 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,1(2):139-147
The energy-pooling rate coefficient for the
process has been measured. The barium atoms were excited by a cw diode laser tuned to the frequency of the 791.3 nm intercombination
line and the metastable atoms in the 6s5d state were produced due to radiative and collisional depopulation of the laser-excited 6s6p state. The measurements were performed at number densities of about and at 30 mbar argon as the buffer gas. Most of the barium ground state atoms in the excitation zone were transferred to
the trip let metastable state at the laser pump power applied. The energy pooling rate coefficient was determined by comparing
the fluorescence intensity of the barium 553.6 nm resonance line and the fluorescence intensity of the intercombination line
791.3 nm. In addition, the populations of the metastable atoms were probed with low intensity laser radiation from a single
mode ring dye laser. The rate coefficient was found to be at .
Received: 11 April 1997 / Revised: 24 September 1997 / Accepted: 10 December 1997 相似文献
9.
1/2 ) atoms in a dense sodium vapour irradiated by nanosecond laser pulses tuned near the 3S→4P transition was investigated. It
was observed that the population of Na(4P) atoms remained high only within the laser pulse, in spite of the relatively long
lifetime of the 4P level (110.ns)The 3P1/2 level, which is populated as a result of cascade transitions from the higher levels, reached the highest population several
nanoseconds after the laser shot. The fast population changes are explained by cascade-stimulated transitions between the
excited atomic levels.
Received: 16 July 1997/Revised version: 27 October 1997 相似文献
10.
E.G. Lariontsev I. Zolotoverkh P. Besnard G.M. Stéphan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(1):107-117
An injected microchip laser is theoretically studied, with the use of two models: in the first model, which is traditional,
the field is represented by a single frequency component in the slowly-varying envelope approximation. In the second model,
referred to as the Fabry-Perot model, two field components are considered which are respectively centered around the frequency
of an eigenmode of the injected laser and the frequency of the injected field. Computation of locking ranges, bistability
do mains are performed and the results compared. They show not only an improved precision of the second model but also a necessity
to use it to describe some effects such as the bistable domains in the limits of the locking domains.
Received: 1st April 1998 / Accepted: 21 August 1998 相似文献
11.
Z.-M. Ren P.-N. Wang Y.-C. Du Z.-F. Ying F.-M. Li 《Applied Physics A: Materials Science & Processing》1997,65(4-5):407-409
2 radicals when the 355 and 1064 nm outputs of a Nd:YAG laser were applied. While for the 532 nm ablation, a relatively higher
concentration of excited atomic carbon was obtained. Different Raman and FTIR spectral features were observed from the deposited
films with different ablation wavelengths. The 532 nm laser ablation is proposed for the synthesis of high quality carbon
nitride films.
Received: 16 October 1996 / Accepted: 11 April 1997 相似文献
12.
J. Badro J.P. Itié A. Polian 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(3):265-268
X-ray diffraction (XRD) experiments have been carried out on quartz-like GaPO4 at high pressure and room temperature. A transition to a high pressure disordered crystalline form occurs at 13.5 GPa. Slight
heating using a YAG infrared laser was applied at 17 GPa in order to crystallize the phase in its stability field. The structure
of this phase is orthorhombic with space group Cmcm. The cell parameters at the pressure of transition are a
=7.306?, b
=5.887? and c
=5.124?.
Received: 7 October 1997 / Received in final form: 17 November 1997 / Accepted: 18 November 1997 相似文献
13.
M. Goldman 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(2):147-156
We describe the theory of EPR in a crystal field multiplet under sample spinning. Berry phases arise because the crystal field
is of lower symmetry than the full rotation group. The formal development is limited to pure J multiplets, crystal field doublets, and field and rotation axes parallel to a principal axis.
Received: 4 August 1997 / Received in final form: 19 December 1997 /
Accepted: 28 January 1998 相似文献
14.
2 laser at 9.676 μm.
Received: 2 December 1996/Revised version: 2 April 1997 相似文献
15.
Ch. Andreeva G. Bevilacqua V. Biancalana S. Cartaleva Y. Dancheva T. Karaulanov C. Marinelli E. Mariotti L. Moi 《Applied physics. B, Lasers and optics》2003,76(6):667-675
We investigate the coherent population trapping effect occurring between the Zeeman sublevels of a given hyperfine state of
Cs when excited by a single-mode diode laser, which is frequency modulated in the kHz–MHz range. In the presence of a dc magnetic
field, simultaneous excitation of pairs of ground-state magnetic sublevels to common excited magnetic sublevels is performed.
As a result, coherent population trapping resonance is detected at only a given modulation frequency, whose value gives a
measure of the magnetic field. The parameters of the resonances are measured in order to determine the ultimate accuracy of
the magnetic field measurement.
Received: 6 December 2002 / Revised version: 24 February 2003 / Published online: 2 June 2003
RID="*"
ID="*"Corresponding author. Fax: +39-0577/23-4689, E-mail: biancalana@unisi.it 相似文献
16.
M. Bouzidi A. Makhoute M.N. Hounkonnou 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(2):159-165
We study the influence of the laser polarization on the electron impact excitation of atomic hydrogen. Our method takes into
account the “dressing” of the target states by including the laser-atom interaction to first order time-dependent perturbation
theory, while the interaction of the laser field with the incident electron is treated to all orders by using the non relativist
Volkov function. The interaction of the fast projectile with the target atom is treated in the first Born approximation. The
calculations are performed via two distinct computations. The first one is based on a direct calculation, the second based on a Sturmian approach. Important
differences appear between the angular distributions depending on the polarization chosen.
Received : 17 february 1998 / Revised : 20 july 1998 / Accepted : 2 september 1998 相似文献
17.
V. Kowalenko 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(2):161-168
The modes of a strongly magnetized charged Bose gas are presented for ultra-low temperatures. For longitudinal oscillations
propagating parallel to the magnetic field the dispersion relation is found to be dominated by the one-dimensional field-free
plasmon dispersion relation as found by Alexandrov, Beere and Kabanov recently in reference [1], while for propagation perpendicular
to the magnetic field they are found to be influenced by the cyclotron motion of the particles. Dispersion relations for these
modes known as Bernstein modes are given near the cyclotron frequency and its first two harmonics. The dispersion relations
for transverse modes in the system are then presented for the cases of photon propagation perpendicular and parallel to the
direction of the magnetic field.
Received: 3 July 1997 / Revised: 12 August 1997 / Accepted: 4 November 1997 相似文献
18.
F. Stietz T.A. Vartanyan J. Viereck T. Wenzel F. Träger 《Applied Physics A: Materials Science & Processing》1998,66(3):367-371
2 were measured as a function of laser fluence, number of laser pulses, and oxygen exposure. If the laser fluence exceeds 10 mJ/cm2 desorption from clean particles occurs as a thermal reaction. Oxygen exposure as low as 1 L causes a strong decrease in the
number of desorbed atoms and dimers. For larger oxygen coverages desorption of Na2O molecules is observed and, surprisingly, the atom signal recovers. At this stage, the underlying mechanism is substantially
different from that for clean particles. The results can be explained by a model that takes into account the formation of
a Na2O layer around a Na core and diffusion of Na atoms through the oxide layer prior to desorption.
Received: 15 December 1997/Accepted: 16 December 1997 相似文献
19.
K. Schröter G. Wilde R. Willnecker M. Weiss K. Samwer E. Donth 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(1):1-5
High-resolution synchrotron-radiation powder diffraction experiments were performed to observe structural changes induced
by hydrogen loading in rapidly-quenched Ti-Zr-Ni alloy ribbons with dominant icosahedral character. Lattice expansion effects
due to hydrogen storage in Ti-Zr-Ni quasicrystals as well as phonon and phason disorder coefficients are obtained from an
analysis of diffraction linewidths.
Received: 26 August 1997 / Revised: 8 January 1998 / Accepted: 10 February 1998 相似文献
20.
V. Uhl K.O. Greulich S. Thomas 《Applied Physics A: Materials Science & Processing》1997,65(4-5):457-462
′ and NBOH). Samples with high OH content exhibit gradual recovery from the absorption band within several minutes after exposure
to the KrF laser radiation.
The formation of the KrF laser-induced 210 nm absorption band depends on the fictive temperature and on the OH content. Low
fictive temperature, as a measure for the number of intrinsic defects, retards E′ generation at the beginning of intense KrF excimer laser irradiation when the majority of defects are generated from precursor
defects. However, for longer irradiation periods with pulse numbers of the order of 105 pulses, a high OH content is the beneficial parameter. The accompanying atomic hydrogen is essential for the suppression
of the 210 nm absorption band. This happens by transformation of the E′ centers into Si-H defects.
In contrast to a generally held view, annealing (decreasing of the fictive temperature) of fused silica does not always reduce
UV induced defect generation. For example, annealing of the samples in an argon atmosphere causes a significantly higher 210 nm
absorption increase during KrF excimer laser irradiation (240000 pulses) compared to nonannealed samples.
Two spectroscopic methods to determine the OH content of fused silica were applied: Raman and infrared spectroscopy, which
in this work lead to differing results.
The energetics of the 210 nm absorption band generation and bleaching is summarized by a diagram explaining the interaction
of the 248 nm laser radiation with fused silica.
Received: 2 June 1997/Accepted: 13 June 1997 相似文献