共查询到20条相似文献,搜索用时 31 毫秒
1.
P. Rosenbusch J.A. Retter B.V. Hall E.A. Hinds F. Lison D. Haubrich D. Meschede 《Applied physics. B, Lasers and optics》2000,70(5):661-663
We have demonstrated that a cobalt single crystal can be used to make a remarkably smooth retro-reflector for cold paramagnetic
atoms. The crystal is cut so that its surface lies in the (0001) plane and the atoms are reflected by the magnetic field above
the surface due to the self-organized pattern of magnetic domains in the material. We find that the reflectivity for suitably
polarized atoms exceeds 90% and may well be unity. We use the angular spread of a reflected atom cloud to measure the roughness
of the mirror. We find that the angular variation of the equivalent hard reflecting surface is (3.1±0.3°)rms for atoms dropped
onto the mirror from a height of 2 cm.
Received: 29 November 1999 / Revised version: 24 February 2000 / Published online: 5 April 2000 相似文献
2.
Improving the specularity of magnetic mirrors for atoms 总被引:1,自引:0,他引:1
G. Zabow M. Drndić J.H. Thywissen K.S. Johnson R.M. Westervelt M. Prentiss 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(3):351-359
An array of anti-parallel current-carrying wires creates an inhomogeneous magnetic field capable of reflecting neutral atoms.
We present analytical and numerical analyses of the magnetic field produced by such an array, and describe methods for reducing
the resulting rms angular deviation from specular reflection to less than 0.1 mrad. Careful choice of cross-sectional wire
profiles is shown to dramatically improve specularity of reflection close to the surface. Additionally, we find that the specularity
depends on whether the number of wires in the mirror is even or odd, and that there exists an optimal turning height above
the surface that maximizes the specularity of reflection from the mirror.
Received 16 November 1998 相似文献
3.
W. Holzer A. Penzkofer T. Pertsch N. Danz A. Bräuer E.B. Kley H. Tillmann C. Bader H.-H. Hörhold 《Applied physics. B, Lasers and optics》2002,74(4-5):333-342
Wave-guided thin-film distributed-feedback (DFB) polymer lasers are fabricated by spin coating a PPV-derived semiconducting
polymer, thianthrene-DOO-PPV, onto oxidised silicon wafers with corrugated second-order periodic gratings. The gratings are
written by reactive ion beam etching. Laser action is achieved by transverse pumping with picosecond laser pulses (wavelength
347.15 nm, duration 35 ps). The DFB-laser surface emission and edge emission are analysed. Outside the grating region the
polymer film is used for comparative wave-guided travelling wave laser (amplified spontaneous emission (ASE)) studies. The
pump pulse threshold energy density for wave-guided DFB-laser action (4–9 μJ cm-2) is found to be approximately a factor of two lower than the threshold for wave-guided travelling wave laser action. The
spectral width of the DFB laser (down to ΔλDFB≈0.07 nm) is considerably narrower than that of the travelling wave laser (ΔλTWL≈14 nm). The DFB-laser emission is highly linearly polarised transverse to the grating axis (TE mode). Only at high pump pulse
energy densities does an additional weak TM mode build up. The surface-emitted DFB-laser radiation has a low divergence along
the grating direction. For both the DFB lasers and the travelling wave lasers, gain saturation occurs at high excitation energy
densities.
Received: 7 January 2002 / Revised version: 15 February 2002 / Published online: 14 March 2002 相似文献
4.
I.F. Salakhutdinov L. Kotačka H.J.W.M. Hoekstra J. Čtyroký V.A. Sychugov O. Parriaux 《Applied physics. B, Lasers and optics》2001,73(5-6):541-545
Abnormal reflecting mirror (ARM) structures, consisting of a corrugated optical waveguiding structure, can serve as a wavelength-selective
end mirror in a laser cavity. The ARM structure shows, for each wavelength in a certain region, 100% reflection at a certain
angle of incidence. In the vicinity of this angle the waveguide is resonantly excited, leading to strong enhancement of the
optical field in the layer structure, which is interesting for efficient second-harmonic generation (SHG). In this paper,
experimental results of a first prototype, exhibiting Čerenkov SHG, are reported.
Received: 16 May 2001 / Revised version: 28 August 2001 / Published online: 30 October 2001 相似文献
5.
《Comptes Rendus de l''Academie des Sciences Series IV Physics》2001,2(4):619-624
We report on experiments on an evanescent-wave mirror for cold 87Rb atoms. Measurements of the bouncing fraction show the importance of the Van der Waals attraction to the surface. We have directly observed radiation pressure parallel to the surface, exerted on the atoms by the evanescent-wave mirror. We analyze the radiation pressure by imaging the motion of the atom cloud after the bounce. The number of photon recoils ranges from 2 to 31. This is independent of laser power, inversely proportional to the detuning and proportional to the evanescent-wave decay length. By operating the mirror on an open transition, we have also observed atoms that bounce inelastically due to a spontaneous Raman transition. The observed distributions consist of a dense peak at the minimum velocity and a long tail of faster atoms, showing that the transition is a stochastic process with a strong preference to occur near the turning point of the bounce. 相似文献
6.
T.J. Davis 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(1):111-118
The diffraction of laser-cooled atoms from a spatially-periodic potential is modelled using rigorous coupled-wave analysis.
This numerical technique, normally applied to light-diffraction, is adapted for use with atomic de Broglie waves incident
on a reflecting diffraction grating. The technique approximates the potential by a large number of constant layers and successively
solves the complex eigenvalue problem in each layer, propagating the solution up to the surface of the grating. The method
enables the diffraction efficiencies to be calculated for any periodic potential. The results from the numerical model are
compared with the thin phase-grating approximation formulae for evanescent light-wave diffraction gratings and idealised magnetic
diffraction gratings. The model is applied to the problem of diffracting Rb atoms from a grating made from an array of permanent
magnets.
Received 13 June 2000 and Received in final form 15 December 2000 相似文献
7.
Influence of radial electric field on trajectories of plug potential bounce ion in the tandem mirror
K. Ishii A. Fueki Y. Takemura A. Kojima H. Hagisawa I. Katanuma K. Yatsu 《Czechoslovak Journal of Physics》2002,52(10):1135-1142
Bouncing ions between the plug potentials play an important role in improvement of the axial confinement in the tandem mirror.
We examined the influence of the radial electric field on the trajectories of the ions passed through the anchor cell with
nonaxisymmetric magnetic configuration on the assumption that the shape of the magnetic flux tube was shifted from the shape
of the equipotential surface of the plasma at the mirror throats of the anchor cells. The discrepancy between the shapes enhanced
the radial drift of the bounce ion. Radial potential profile of the core plasma was controlled by adjustment of the radially
separated endplate potentials, and it was found that the flattened radial potential profile was effective for the decrease
of the radial drift.
Presented at 5th Workshop “Role of Electric Fields in Plasma Confinement and Exhaust”, Montreux, Switzerland, June 23–24,
2002. 相似文献
8.
J. Schmiedmayer 《Applied physics. B, Lasers and optics》1995,60(2-3):169-179
We present new ways of trapping a neutral atom with static electric and magnetic fields. We discuss the interaction of a neutral atom with the magnetic field of a current carrying wire and the electric field of a charged wire. Atoms can be trapped by the 1/r magnetic field of a current-carrying wire in a two-dimensional trap. The atoms move in Kepler-like orbits around the wire and angular momentum prevents them from being absorbed at the wire. Trapping was demonstrated in an experiment by guiding atoms along a 1 m long current-carrying wire. Stable traps using the interaction of a polarizable atom with the electric field of a charged wire alone are not possible because of the 1/r
2 form of the interaction potential. Nevertheless, we show that one can build a microscopic trap with a combination of a magnetic field generated by a current in a straight wire and the static electric field generated by a concentric charged ring which provides the longitudinal confinement. In all of these traps, the neutral atoms are trapped in a region of maximal field, in theirhigh-field seeking state.Dedicated to H. Walther on the occasion of his 60th birthday 相似文献
9.
T.J. Davis 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(3):289-297
The problem of atom diffraction from a reflecting magnetic diffraction grating is solved in the thin phase-grating approximation.
The general problem for scalar diffraction is modelled using a semi-classical method in which the grating potential is separated
into a reflecting term and a diffracting term. The trajectory of the atom in the reflecting potential is solved classically
and the atom wave function in the diffracting potential found by integrating the phase change along the classical trajectory.
The diffraction orders are obtained after Fourier transforming the result. This can be done independently of the grating potential
resulting in a general formula for the diffraction efficiencies. The general result is applied to the problem of atom diffraction
from a magnetic grating. Several approximations are required to reduce the problem to a form amenable to analytic solution.
The results are compared with an accurate numerical method.
Received 1st February 2001 and Received in final form 8 March 2001 相似文献
10.
Y. Manzhur W.-D. Zeitz M. J. Prandolini W. D. Brewer P. Imielski J. Schubert K. Johnston 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(3):277-283
Using refined preparation techniques, cadmium guest atoms have been
positioned at different sites on the surfaces of nickel crystals. The
magnetic hyperfine fields and the electric field gradients at the Cd nuclei
were measured by time-dependent perturbed angular correlation (TDPAC)
spectroscopy of the emitted gamma radiations. By measuring the combined
interactions, electric field gradients and magnetic hyperfine fields can be
unambiguously attributed to each surface site. The signs of the magnetic
hyperfine fields are determined by applying an external magnetic field and
choosing the appropriate γ-ray detector configuration. The measured
fields correlate with the number of neighbouring host atoms. Band structure
calculations confirm this finding and predict magnetic fields for various
sp elements from the band structure of the s-like conduction electrons. The
quadrupolar interactions are manifestations of the balance in the occupation
of the guest p-sublevels. These results provide new information on the
structure and formation of electronic configurations of sp elements in different local environments and will contribute to understanding electronic effects on surfaces. 相似文献
11.
We develop a phenomenological model of the double-phase-conjugate mirror grating formation based on geometrical considerations.
We show that the grating develops from one lateral side of the interaction zone towards the other side. This model is confirmed
by the behaviour of different configurations of a 2-zone double-phase-conjugate mirror. Finally, we obtained stable operation
in InP:Fe, this made it possible to implement a 1×8 switch between single-mode fibres at telecom wavelength with 12% global
efficiency and 200 ms reconfiguration time.
Received: 6 November 1998 / Revised version: 18 February 1999 / Published online: 7 April 1999 相似文献
12.
软X射线谱学显微光束线单色器结构设计及精度测试 总被引:2,自引:0,他引:2
针对上海光源谱学显微光束线站的性能要求,对其核心部件单色器进行结构设计。阐述了单色器的扫描运动原理,论述了波长扫描机构的设计方案,具体分析平面镜和光栅的转角重复精度影响因素;描述光栅切换机构,着重分析其水平偏差、垂直偏差、滚角、摆角和投角的精度问题;采用六杆并联机构的方案完成镜箱调节机构的设计,分析其支杆的调节范围和分辨力情况。给出了单色器的结构,并且对其精度进行了测试。测试结果表明,平面镜和光栅的转角重复精度分别为0.166″和0.149″;光栅切换机构的滚角、摆角和投角的重复精度分别为0.08″、0.12″和0.05″。这说明了单色器的结构设计方案和机械精度满足技术要求。 相似文献
13.
Magneto-Optic Fiber Gratings Useful for Dynamic Dispersion Management and Tunable Comb Filtering
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Intelligent control of dispersion management and tunable comb filtering in optical network appfications can be performed by using magneto-optic fiber Bragg gratings (MFBGs). When a nonuniform magnetic field is applied to the MFBG with a constant grating period, the resulting grating response is equivalent to that of a conventional chirped grating. Under a linearly nonuniform magnetic field along the grating, a linear dispersion is achieved in the grating bandgap and the maximal dispersion slope can come to 1260ps/nm2 for a l0-mm-long fiber grating at 1550nm window. Similarly, a Gaussian-apodizing sarnpled MFBG is also useful for magnetically tunable comb filtering, with potential application to clock recovery from return-to-zero optical signals and optical carrier tracking. 相似文献
14.
A Continuously Tunable Erbium-Doped Fibre Laser Using Tunable Fibre Bragg Gratings and Optical Circulator
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A continuously tunable erbium-doped fibre laser (TEDFL) based on tunable fibre Bragger grating (TFBG) and a three-port optical circulator (OC) is proposed and demonstrated. The OC acts as a 100%-reflective mirror. A strain-induced uniform fibre Bragger grating (FBG) which functions as a partial-reflecting mirror is implemented in the linear cavity. By applying axial strain onto the TFBG, a continuously tunable lazing output can be realized. The wavelength tuning range covers approximately 7.00nm in C band (from 1543.6161 to 1550.3307nm). The side mode suppression ratio (SMSR) is better than 50 dB, and the 3 dB bandwidth of the laser is less than 0.01 nm. Moreover, an array waveguide grating (AWG) is inserted into the cavity for wavelength preselecting, and a 50 km transmission experiment was performed using our TEDFL at a 10 Gb/s modulation rate. 相似文献
15.
Waveguide grating mirror for large-area semiconductor lasers 总被引:1,自引:0,他引:1
We have fabricated and tested a waveguide grating mirror that uses anomalous reflection of light associated with excitation of waveguide modes. Sharp features are observed in the reflection spectra in both the wavelength and the angular domains. We confirm experimentally that, when the waveguide grating mirror is placed a short distance in front of a large-area semiconductor laser, it can control the emission spectrum. This demonstration opens a new approach to the design of very compact semiconductor lasers operating in the single-frequency-single-mode regime. 相似文献
16.
As it is known [1] an intense laser field can induce atom-atom interaction according to a dipole-dipole R
–3 law. Such an interaction depends on the angle between light polarization and interatomic vector-position R. This angular dependence may produce an anisotropy in the spatial density distribution of the confined sample of cold atoms. We develop the main relations and apply them to the case of an atomic cloud of cold trapped neutral atoms with the density higher than or of the order of –3, where is the wavelength of light. The results presented here show the effect of such an interaction in a density regime of high experimental interest. 相似文献
17.
Yu-Lei Wang Hong-Li Wang Yi Chen Wei-Ming He Rui-Qing Fan Zhi-Wei Lv 《Journal of Russian Laser Research》2016,37(3):302-307
We propose a grating semi-feedback external cavity (GSFEC) scheme for high-power broad-area laser diodes for improving the spectrum characteristics of high-power semiconductor lasers. We design this scheme as two crossed cylindrical resonators employing a holographic diffraction grating and a rectangular highly reflecting mirror. In our experiments, we obtain stable spectrum characteristics over a tuning range of 5 nm, with maximum output power up to 764 mW at an operating current of 3.5 A. The wavelength drift rate with injection current decreases from 0.59 nm/A of free-running condition to 0.2 nm/A, and the laser bandwidth is compressed to 21.5% at 2 A. 相似文献
18.
Hafizi B. Sprangle P. Fisher A. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1994,22(5):666-673
The linear and nonlinear operation of a multiwave grating free-electron laser is described. The radiation is generated by the passage of an annular electron beam through a coaxial waveguide, the central conductor being in the form of a corrugated cylinder. The model includes the effects of self-field forces, beam emittance and gyromotion of electrons in a guide magnetic field. The efficiency is determined by numerical simulation and compared with analytical estimates. A compact source utilizing, for example, a high brightness beam from a carbon fibre electron gun, that is tunable in the wavelength band 35-55 μm with output in the kilowatt range, is shown to be feasible 相似文献
19.
20.
We have experimentally demonstrated a material-independent mirror for atomic waves that uses the Fresnel diffraction at an array of parallel ridges. He* (2 (3)S(1)) and Ne* (1s(3)) atomic waves were reflected coherently on a silicon plate with a microfabricated grating structure, consisting of narrow wall-like ridges. We measured the reflectivity at grazing incidence as a function of the incident velocity and angle. Our data show that the reflectivity on this type of mirror depends only on the distance between the ridges, the wavelength, and the incident angle, but is insensitive to the material of the grating structure. The reflectivity is observed to increase by 2 orders of magnitude, compared to that of a flat polished silicon surface, where the reflection is caused by the attractive surface potential. For He* atoms, the measured reflectivity exceeds 10% for normal incident velocities below about 25 cm/s. 相似文献