共查询到20条相似文献,搜索用时 15 毫秒
1.
D. Fröhlich T. Kiefer S. Leute T. Lottermoser 《Applied physics. B, Lasers and optics》1999,68(3):465-471
ijk and on their phase. One of the hexagonal manganites, YMnO3 is chosen to demonstrate in detail the experimental methods for obtaining this information. The interference of different
contributions is utilized to study domain topography.
Received: 26 October 1998 相似文献
2.
M. Fiebig D. Fröhlich S. Leute R.V. Pisarev 《Applied physics. B, Lasers and optics》1998,66(3):265-270
2 O3, in which the time-invariant second-harmonic reference can be generated either intrinsically by the crystal or externally
by use of the new technique, so that both methods may be compared. The technique is then used to visualize the domain structure
of YMnO3, an antiferromagnetic crystal which does not provide the time-invariant reference wave intrinsically. The experiments demonstrate
the wide applicability of the method.
Received: 13 June 1997 相似文献
3.
T. Lottermoser M. Fiebig D. Fröhlich S. Kallenbach M. Maat 《Applied physics. B, Lasers and optics》2002,74(7-8):759-764
Second-harmonic generation (SHG) is used as a probe for the coexisting ferroelectric and antiferromagnetic orders in hexagonal
RMnO3. SH contributions coupling to the electric and/or magnetic order parameters are identified on the basis of their spectral
dependence and the symmetries of the corresponding order parameters. The SH signals from the ferroelectric and antiferromagnetic
orders were employed to image the electric and magnetic domain structures separately. The transformation properties of electric
and magnetic domains are discussed with respect to the transformation properties of the corresponding order parameters. An
investigation of the mutual coupling between the coexisting electric and magnetic orders reveals apparently independent domain
structures, which contradicts the symmetry and transformation properties of electric-dipole-induced SHG in this ferroelectromagnetic
group of compounds. Apart from higher-order multipole contributions to SHG, interface contributions from clamped electric
and magnetic domains can solve the contradiction.
Received: 16 October 2001 / Published online: 24 April 2002 相似文献
4.
5.
Influence of optical-damage-resistant dopants on the nonlinear optical properties of lithium niobate
Using the chemical-bond method, nonlinear optical properties of lithium niobate containing different dopants are calculated.
In crystals with stoichiometric composition the second order nonlinear susceptibility decreases approximately linearly with
increasing dopant concentration. Among the dopants studied – Mg, Zn and In – this behaviour is most highly expressed for In
doping. In contrast to that, congruently grown crystals show a different behaviour; only a weak dependence on the dopant concentration
is found for, for example, Mg-doped material.
Received: 24 October 2000 / Published online: 21 March 2001 相似文献
6.
4 (KTA) optical parametric oscillator (OPO) synchronously pumped by a cw diode-pumped mode-locked Nd:YVO4 oscillator–amplifier system. The laser system (pumped by 84 W of cw 808-nm diode radiation) generates 7-ps-long pulses at
1.064 μm with a repetition rate of 83.4 MHz and an average power of 29 W. The OPO, synchronously pumped by the 1.064-μm laser
pulses, consists of a 15-mm-long KTA crystal (cut for type II noncritical phase-matching) in a folded signal resonant linear
resonator. The average powers of the 1.54-μm signal radiation and the 3.47-μm idler radiation are 14.6 W and 6.4 W, respectively.
The total OPO output of 21 W corresponds to an internal efficiency of 75%. The experimental investigations include measurements
of the OPO output power (and its dependence on the pump power, the transmission of the output coupler, and the resonator length)
and of the pulse properties (such as pulse duration and spectral width). The measured results are in good agreement with the
predictions of a numerical analysis based on a split-step Fourier method.
Received: 4 May 1998 相似文献
7.
Y.R. Shen 《Applied physics. B, Lasers and optics》1999,68(3):295-300
Received: 20 September 1998 相似文献
8.
T.V. Dolgova V.G. Avramenko A.A. Nikulin G. Marowsky A.F. Pudonin A.A. Fedyanin O.A. Aktsipetrov 《Applied physics. B, Lasers and optics》2002,74(7-8):671-675
Size effects in the resonant nonlinear optical response of amorphous Si/SiO2 multiple quantum wells (MQW) are studied by second-harmonic generation (SHG) spectroscopy in a spectral interval of second-harmonic
photon energies from 2.5 to 3.4 eV. The sensitivity of SHG spectroscopy to thickness-dependent electronic structure (sub-band
energy position and density of states line shape) of MQW is demonstrated. A monotonic red shift of central energies of SHG
resonances by 120 m eV upon increase of the well thickness from 2.5 to 10 ? is observed. This is interpreted as a size dependence
of the position of singularities in the combined density of states for a 2D gas of electrons moving in an effective potential
well. It is shown that, for agreement with experiment, the simplest (rectangular) shape of the well should be modified in
order to take into account the lattice-potential distortion at the interfaces.
Received: 16 October 2001 / Revised version: 16 April 2002 / Published online: 6 June 2002 相似文献
9.
3 O5 (LBO) crystal has been studied by using the bond valence theory of complex crystals. Chemical bond parameters and linear
and nonlinear optical (NLO) properties of each type of constituent chemical bonds are quantitatively determined. Because of
the different crystal structure characteristics of LBO from those of β-BaB2O4 (BBO), the two anionic groups, (B3O7)5- in LBO and (B3O6)3- in BBO, play different roles in contributions to their own total NLO tensor coefficients of LBO and BBO, respectively. By
comparison, we find that planar (B3O6)3- groups are the ideal structure model, leading to little cancellation of contributions of each kind of bond in these groups,
and this gives us a useful guide to design new NLO materials in the future.
Received: 24 January 1997/Accepted: 27 March 1997 相似文献
10.
E.D. Mishina A.I. Morosov Q.-K. Yu S. Nakabayashi T. Rasing 《Applied physics. B, Lasers and optics》2002,74(7-8):765-775
A general approach of second-harmonic generation (SHG) studies for surface phase transitions (PTs) is presented, with a thermodynamic
classification of surface PTs and their relation to SHG parameters. The symmetry aspects of SHG near a surface PT are discussed,
including issues connected with separation of surface and bulk contributions and the role of atomic and mesoscopic inhomogeneities.
This approach is illustrated by applying it to two systems revealing a (near-) surface PT: single-crystalline SrTiO3 near a bulk structural PT and single-crystalline Au in an electrochemical cell revealing an order–disorder and a reconstructive
PT.
Received: 15 January 2002 / Published online: 11 June 2002 相似文献
11.
W. Wulfhekel H.F. Ding W. Lutzke G. Steierl M. Vázquez P. Marín A. Hernando J. Kirschner 《Applied Physics A: Materials Science & Processing》2001,72(4):463-470
We give an overview over our recent efforts of high-resolution magnetic imaging using scanning tunneling microscopy with a
ferromagnetic tip. Magnetic sensitivity is obtained on the basis of local tunneling magnetoresistance between a soft magnetic
tip and the sample. The magnetisation of the tip is switched periodically with a small coil, leading to variations of the
tunneling current due to the tunneling magnetoresistance effect. These variations are detected with a lock-in amplifier to
separate spin-dependent parts from the topographic parts of the tunneling current such that the topography and the magnetic
structure of the sample can be recorded simultaneously. Crucial for this method is to avoid mechanical vibrations of the tip,
that may also lead to variations in the tunneling current. Exemplary studies of polycrystalline Ni and the closure domain
pattern of Co(0001) are presented, showing high contrast at acquisition times as low as 3 ms/pixel and a lateral resolution
of the order of 1 nm. Further it is demonstrated that besides topography and magnetisation, also local information about the
magnetic susceptibility can be obtained.
Received: 28 April 2000 / Accepted: 15 May 2000 / Published online: 7 March 2001 相似文献
12.
Large magnetoresistance (MR) has been observed in Ni1-
x
S (x=-0.02, -0.01, 0, 0.01, 0.02 and 0.03). The MR in a magnetic field of 4 T was found to be equal to 770% at 290 K for x=-0.02, 920% at 283 K for x=-0.01, 1530% at 268 K for x=0, 1040% at 230 K for x=0.01, 730% at 257 K for x=0.02 and 660% at 87 K for x=0.03. The large MR was found to be due to a magnetic field-induced magnetic and electrical transition from an antiferromagnetic
(AFM) anomalous-metal phase to a paramagnetic (PM) metal phase.
Received: 23 January 2001 / Accepted: 24 January 2001 / Published online: 27 June 2001 相似文献
13.
Received: 4 May 1998/Revised version: 8 July 1998 相似文献
14.
A. Kummrow M. Wittmann F. Tschirschwitz G. Korn E.T.J. Nibbering 《Applied physics. B, Lasers and optics》2000,71(6):885-887
We demonstrate the generation of ultraviolet 33-fs pulses with a shot-to-shot energy fluctuation of less than 3% using sum
frequency mixing of visible pulses of a noncollinear optical parametric amplifier with sub-40-fs pulses of a 1-kHz Ti:sapphire-amplified
system. The pulses are transform-limited (ΔνΔτ=0.36) and tunable in the range from 315 nm to 355 nm with energy above 1 μJ
(2.6 μJ at 330 nm).
Received: 21 July 2000 / Published online: 8 November 2000 相似文献
15.
P.S. Parkinson D. Lim R. Büngener J.G. Ekerdt M.C. Downer 《Applied physics. B, Lasers and optics》1999,68(3):641-648
0.9 Ge0.1(001)/Si(001) films with SH photon energies 3.1<2hν<3.5 eV near the bulk E1 critical point of Si(001) or Si0.9Ge0.1(001). Ge was deposited on Si(001) by using atomic layer epitaxy cycles with GeH4 or Ge2H6 deposition at 410 K followed by hydrogen desorption. As Ge coverage increased from 0 to 2 monolayers the SH signal increased
uniformly by a factor of seven with no detectable shift in the silicon E1 resonant peak position. SH signals from Si0.9Ge0.1(001)/Si(001) were also stronger than those from intrinsic Si(001). Hydrogen termination of the Si0.9Ge0.1(001) and Ge/Si(001) surfaces strongly quenched the SH signals, which is similar to the reported trend on H/Si(001). We attribute
the stronger signals from Ge-containingsurfaces to the stronger SH polarizability of asymmetric Ge-Si and Ge-Ge dimers compared
to Si-Si dimers. Hydrogen termination symmetrizes all dimers, thus quenching the SH polarizability of all of the surfaces
investigated.
Received: 13 October 1998 / Revised version: 18 January 1999 相似文献
16.
Four-wave mixing of picosecond pulses in hollow fibers: expanding the possibilities of gas-phase analysis 总被引:2,自引:0,他引:2
A.B. Fedotov F. Giammanco A.N. Naumov P. Marsili A. Ruffini D.A. Sidorov-Biryukov A.M. Zheltikov 《Applied physics. B, Lasers and optics》2001,72(5):575-582
Third-harmonic, difference-frequency, and sum-frequency generation processes in hollow fibers are experimentally studied with
30-ps pulses having an energy of several millijoules. The experimental dependence of the difference-frequency signal on the
pressure of the gas filling the fiber agrees well with the results of calculations when the contribution of higher order waveguide
modes is taken into consideration, thus indicating the importance of nonlinear-optical processes involving higher order waveguide
modes of a hollow fiber. Hollow fibers are also shown to expand the possibilities of nonlinear-optical analysis of gases by
allowing the generation of third-harmonic and sum-frequency signals, which vanish in the regime of tight focusing in a medium
with normal dispersion.
Received: 26 September 2000 / Revised version: 15 January 2001 / Published online: 30 March 2001 相似文献
17.
Dispersion of second-order nonlinear optical coefficient 总被引:2,自引:0,他引:2
J. Seres 《Applied physics. B, Lasers and optics》2001,73(7):705-709
A simple, approximate relation between the dispersion of the second-order nonlinear optical (SNLO) coefficient and first-order
susceptibility has been derived using the well-known results of density-matrix calculation of quantum-mechanical theory. A
new tensor of SNLO coefficient has been defined, which retains symmetries when the input beams are in the spectral range of
transparency while the generated beam can also be in the spectral range of absorption. The validity of the relation has been
checked for three ferroelectric crystals, KTP, LiNbO3 and KNbO3, which are transparent in the visible and near infrared, and for two semiconductors, GaP and GaAs, which absorb in the visible.
Contrary to Miller’s law, the presented relation is in good agreement with measurements.
Received: 8 February 2001 / Revised version: 2 July 2001 / Published online: 10 October 2001 相似文献
18.
Carrier-envelope offset phase control: A novel concept for absolute optical frequency measurement and ultrashort pulse generation 总被引:5,自引:0,他引:5
H.R. Telle G. Steinmeyer A.E. Dunlop J. Stenger D.H. Sutter U. Keller 《Applied physics. B, Lasers and optics》1999,69(4):327-332
The shortest pulses periodically emitted directly from a mode-locked Ti:sapphire laser are approaching the two-optical-cycle
range. In this region, the phase of the optical carrier with respect to the pulse envelope becomes important in nonlinear
optical processes such as high-harmonic generation. Because there are no locking mechanisms between envelope and carrier inside
a laser, their relative phase offset experiences random fluctuations. Here, we propose several novel methods to measure and
to stabilize this carrier-envelope offset (CEO) phase with sub-femtosecond uncertainty. The stabilization methods are an important
prerequisite for attosecond pulse generation schemes. Short and highly periodic pulses of a two-cycle laser correspond to
an extremely wide frequency comb of equally spaced lines, which can be used for absolute frequency measurements. Using the
proposed phase-measurement methods, it will be possible to phase-coherently link any unknown optical frequency within the
comb spectrum to a primary microwave standard. Experimental studies using a sub-6-fs Ti:sapphire laser suggesting the feasibility
of carrier-envelope phase control are presented.
Received: 19 August 1999 / Published online: 8 September 1999 相似文献
19.
C. Dölle C. Reinhardt P. Simon B. Wellegehausen 《Applied physics. B, Lasers and optics》2002,75(6-7):629-634
. Investigations of the efficient generation of powerful coherent radiation at 82.8 nm by frequency tripling of short-pulse
KrF laser radiation are presented. Argon gas is selected as nonlinear medium due to the resonantly enhanced 3rd-order susceptibility
χ(3)(-3ω,ω,ω,ω). Pulse energies of 100 μJ at 82.8 nm have been measured for a pump pulse energy of 14 mJ. An upscaling to more
than 500 μJ is expected with available more powerful pump lasers. Features of this XUV source and possible applications are
discussed.
Received: 26 July 2002 / Published online: 15 November 2002
RID="*"
ID="*"Corresponding author. Fax: +49-511/7622211, E-mail: reinhardt@iqo.uni-hannover.de 相似文献
20.
A. Kubetzka O. Pietzsch M. Bode R. Wiesendanger 《Applied Physics A: Materials Science & Processing》2003,76(6):873-877
During the last few years, spin-polarized scanning tunneling microscopy and spectroscopy has been developed as a reliable
tool to image surface magnetic domain structures of bulk materials as well as thin films and nanostructured systems. In principle,
this technique also allows for the determination of the energy-resolved spin polarization of the sample PS(E) with nanometer resolution, information which might play a crucial role in understanding systems like, for example, non-magnetic
adatoms on magnetic surfaces. A main problem in quantifying PS(E), however, arises from the fact that, in contrast to planar junctions, the tip–sample distance generally varies with the
magnitude and direction of the surface magnetization, since the distance is controlled indirectly by the tunneling current
that is itself spin-polarized. We employ a simple model of the tunneling process to investigate this issue and show that a
normalization of the dI/dU spectra with the total conductance I/U is insufficient to correct for their distance dependence.
Received: 2 September 2002 / Accepted: 2 September 2002 / Published online: 5 March 2003
RID="*"
ID="*"Corresponding author. Fax: +49-40/42838-5311, E-mail: kubetzka@physnet.uni-hamburg.de 相似文献