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61.
We demonstrate the influences of optical feedback from an external mirror with high reflectivity in a He-Ne laser on self-mixing interference fringes and laser polarization states. When the external mirror is tilted to a certain level, the stable and uniform nanometer resolution fringes are generated. The fringe density is 40 times than that of the conventional self-mixing interference or two beam interference, and has still potential to be improved. Each self-mixing interference fringe corresponds to λ/80 displacement of the external mirror, i.e. 7.91 nm displacement of the external mirror. Moreover, when the movement direction of the external mirror is changed, the polarization flipping between two eigenstates will happen. The potential applications of the results are also discussed. 相似文献
62.
M.?PellarinEmail author E.?Cottancin J.?Lermé J.L.?Vialle M.?Broyer F.?Tournus B.?Masenelli P.?Mélinon 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,25(1):31-40
At the Prague Asterix Laser System Center (PALS) the Asterix iodine laser delivering up to 700 J/0.5 ns is used as a pump
source for X-ray laser experiments and applications. The prepulse technique was applied which is known to improve the neon-like
X-ray laser output at the J = 0-1 transition dramatically. Since Zn slab targets were used the operating wavelength was 21.2 nm. A prepulse having up
to 20 J precedes the main pulse by 10 ns. The main beam and the prepulse beam are focussed by two different optical systems
separately and their foci are superimposed at the target surface. By implementing a half-cavity set-up for double-pass amplification
using a Mo/Si multilayer mirror - which can be used for more than 100 shots - the X-ray laser output was more than 10 times
stronger than at the single pass in a 30 mm long plasma. Double-pass amplification was observed to be most efficient when
the pump pulse duration was at least 150 ps longer than the round trip time ( ≈ 260 ps) in the half-cavity. Under this fundamental
condition the X-ray laser reached saturation in the double-pass regime containing approx. 4 mJ energy which has been proved
to be enough for future applications. In this contribution, the X-ray laser features like divergence in two dimensions, the
beam quality (symmetry), the pointing angle and the integrated intensity giving an estimation of the output energy are investigated
over 110 shots. To characterize the stability of the X-ray laser the shot distribution, the mean value and the standard deviation
for these parameters are evaluated. For 18 shots in a series - what was achievable during one day - the corresponding values
are given, and a statistical analysis carrying out a chi-squared test characterize the Zn X-ray laser as a robust tool suitable
for applications. In the future it is planned to allocate X-ray laser beam time to external research groups.
Received 17 May 2002 / Received in final form 10 September 2002 Published online 6 November 2002
RID="a"
ID="a"e-mail: praeg@fzu.cz 相似文献
63.
Ito S. Ishikawa H. Miura T. Takasago K. Endo A. Torizuka K. 《Applied physics. B, Lasers and optics》2003,76(5):497-503
We present a 7-TW Ti:sapphire laser system operating at 50 Hz for laser Compton femtosecond X-ray generation. This laser system
delivers 8.4 W of average output power at a repetition rate of 50 Hz with a pulse width of 24 fs. It demonstrates successful
management using a dynamically stable resonator in the regenerative amplifier and compensation for thermal lensing by a convex
mirror in a ring-type four-pass power amplifier. We also present the results of closed-loop corrections for distorted wavefronts
of amplified and compressed laser pulses, using an adaptive optical system consisting of a Shack–Hartmann-type wavefront sensor
and a deformable mirror. This closed-loop correction results in dramatic improvements, reducing wavefront distortions below
0.05 λ rms.
Received: 31 October 2002 / Revised version: 3 March 2003 / Published online: 5 May 2003
RID="*"
ID="*"Corresponding author. Fax: +81-298/61-3349, E-mail: ito@festa.or.jp 相似文献
64.
P. Cluzeau F. Bougrioua G. Joly L. Lejček H. T. Nguyen 《Czechoslovak Journal of Physics》2004,54(3):365-376
A simplified model of an inclusion represented by (+1)-wedge disclination and an accompanying hyperbolic defect ((−1)-wedge
disclination) in smectic C* free standing films is used to describe the early stage of the ordering process of inclusions
into chains. The elastic interaction between inclusions and their associated hyperbolic defects is used to discuss the dynamics
observed experimentally during the inclusion chaining when inclusions are at distances much larger than their radii.
This work was also supported by Grant No. 202/02/0840 of the Grant Agency of the Czech Republic and by the research project
AV0Z1-010-914. 相似文献
65.
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
66.
Tasinkevych M Silvestre NM Patrício P Telo da Gama MM 《The European physical journal. E, Soft matter》2002,9(4):341-347
The interaction between two disks immersed in a 2D nematic is investigated i) analytically using the tensor order parameter
formalism for the nematic configuration around isolated disks and ii) numerically using finite-element methods with adaptive
meshing to minimize the corresponding Landau-de Gennes free energy. For strong homeotropic anchoring, each disk generates
a pair of defects with one-half topological charge responsible for the 2D quadrupolar interaction between the disks at large
distances. At short distance, the position of the defects may change, leading to unexpected complex interactions with the
quadrupolar repulsive interactions becoming attractive. This short-range attraction in all directions is still anisotropic.
As the distance between the disks decreases, their preferred relative orientation with respect to the far-field nematic director
changes from oblique to perpendicular.
Received 1 October 2002 and Received in final form 12 November 2002
RID="a"
ID="a"e-mail: miko@cii.fc.ul.pt 相似文献
67.
A.K. Das M. Ehara H. Nakatsuji 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(2):195-200
Excited states of the s, p, and d symmetries up to principal quantum number n = 4 are studied for the first eight members of Ne isoelectronic sequence (Ne to Cl7+) by the SAC-CI (symmetry-adapted-cluster configuration-interaction) method. The valence STO basis sets of Clementi et al. and the optimized excited STO are used by the STO-6G expansion method. The calculated transition energies agree well with
the experimental values wherever available.
Received 26 July 2000 and Received in final form 14 September 2000 相似文献
68.
Zhi-Hao Wu Chih-Huang LaiSheng-Huang Huang Wei-Chi Lin 《Journal of magnetism and magnetic materials》2006
Spin valves composed of TbCo/CoFe/Cu/CoFe/TbFeCo were fabricated with perpendicular magnetization and GMR ratios of 4.5%. The (TbCo/CoFe) layers and (CoFe/TbFeCo) layers are referred to the free and the pinned layers, respectively. The compositions of two layers were chosen to have a lower Curie temperature (130 °C) but higher coercivity (13.2 kOe) of the free layer at room temperature than those of the pinned layer; therefore, the free layer is quite stable at room temperature but its magnetization can be easily switched at a relatively low temperature. Spin valves were patterned into 100-μm-wide cells and their coercivity was reduced with increasing writing current due to the temperature rise by current-heating. When the current density of the writing current was increased to 2.1×106 A/cm2, the required switching field for the free layer was only 10 Oe. 相似文献
69.
The active mode-locking process of the multimode laser with an external pump modulation is theoretically investigated in the frequency domain within the framework of the continuous-mode approximation. Intermode interaction and mode-coupling effects, including both AM and FM modulations, are naturally considered in a hierarchical equation of the mode components derived from the multimode Maxwell-Bloch equations. It is reduced to a continuous-mode equation that can be solved analytically in a stationary case, and used to discuss the spectral line shape and the phase dynamics of mode-components as a function of modulation amplitude and detuning of the modulation frequency. We predict a novel oscillation existing below the threshold of the ordinary complete mode-locking: The intensity of the total electric field yields a stable pulse train but its phase varies irregularly in time. This semi-locked state is characterized by a nonlinear chirping, an asymmetric spectrum, and drifting phases of the field mode-components. 相似文献
70.
Single crystals of YbRhIn5 and YbIrIn5 have been grown by flux method. The crystals were characterized by means of X-ray diffraction, magnetic and electrical transport measurements. Both compounds were found to be weak diamagnets with metallic character of the electrical conductivity and the Seebeck coefficient. 相似文献