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1.
Intense picosecond light pulses of a mode-locked Nd: glass laser at
L
=1054 nm (fundamental wavelength) and
SH
=527 nm (second harmonic wavelength) are passed through a sample of D2O under self-focusing conditions. Spectrally structured superbroadened, spatially bell-shaped emission in the forward direction is obtained. Primary generation processes are pump-pulse-degenerate stimulated parametric four-photon interaction (1 + 1 3 + 4) and stimulated Raman scattering (1
R
+ ), which occur concurrently (1=
L
or
SH
angular pump frequency, #x03C9;
R
first Stokes frequency, #x03C9; signal frequency, #x03C9;3 signal frequency, #x03C9;4 idler frequency). The parametric four-photon interaction occurs under collinear non-phase-matched conditions and under longitudinally phase-matched, transversally non-phase-matched (erenkov-like) conditions. Subsequent interaction processes are pump-pulse-nondegenerate four-photon interaction of the type 1 +
R
3 + 4, coherent antiStokes Raman scattering (CARS, 1 + 1 – 4 3), inverse Raman scattering (
A
+ 1 + ), and cascading light up-conversion of the type 1 +
(i)
–
R
(i+1). 相似文献
2.
G. R. J. Williams 《Applied physics. B, Lasers and optics》1996,63(1):47-50
Excited-State Absorption (ESA), Two-Photon Absorption (TPA) and the third-order polarizability (;,, – ) have been investigated for a model dichloride derivative of a symmetrically substituted benzylidene analine (SBAC), using a multielectron configuration-interaction procedure. The calculations indicate that SBAC exhibits ESA across the visible region of the spectrum, but that it is not as extensive as for molecules such as the phthalocyanines. The magnitude of the third-order polarizability is dominated by resonance enhancement from a very strongA
g
B
u
one-photon absorption. The calculated off-resonance value for (;,, – ) suggests that SBAC is a potential candidate for ultrafast switching applications. 相似文献
3.
H. J. Eichler H. Fery J. Knof J. Eichler 《Zeitschrift für Physik B Condensed Matter》1977,28(4):297-306
Third-order nonlinear optical susceptibilities of different crystals have been measured relative to LiNbO3 by observing collinear phase-matched difference frequency generation
1=2
2–
4. The two incident light waves have been produced by a ruby laser (
2,
2=694.3 nm) and by induced Raman scattering (
4,
4=765.8 nm). With noncollinear phase-matching the number of nonlinear processes and the possibilities to determine nonlinear coefficients is much larger than in the collinear case. Therefore the theory of Raman-type third order interactions has been extended to noncollinear propagation of the interacting waves. The theory has been tested experimentally for CdS. 相似文献
4.
We consider the possibility of electromagnetic wave generation in a plasma with Pe>Be by tail electrons which scatter on anomalous Doppler resonance of potential waves with 2Be. These oscillations, organized into periodic waves, resonantly excite potential waves of harmonic frequencies 1=s·2Pe, s=2, 3, .., easily transformable to electromagnetic radiation. A coherent mechanism for solar radio flares is developed.Deceased.Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 118–122, July, 1994. 相似文献
5.
Matthew J. Donald 《Communications in Mathematical Physics》1991,136(3):625-632
Let (
n
)
n
1 be a norm convergent sequence of normal states on a von Neumann algebraA with
n
. Let (k
n
)
n1
be a strongly convergent sequence of self-adjoint elements ofA withk
n
k. It is shown that the sequence
of perturbed states converges in norm to
. A related result holds forC
*-algebras. A counter-example is provided to show that it is not sufficient to assume weak convergence of (
n
)
n
1 even whenk
n=k for alln. However, conditions are given which, together with weak convergence, are sufficient. Relative entropy methods are used, and a relative entropy inequality is proved. 相似文献
6.
J. Nolting H. Kunze I. Schütz R. Wallenstein 《Applied physics. B, Lasers and optics》1990,50(5):331-344
Resonant third-order sum-frequency mixing of continuous-wave visible and ultraviolet laser light is investigated in the metal vapors of Sr, Ca, Mg, and Zn. The laser radiation (with the frequencies 1, 2, and 3) is generated by single-mode dye- and argonion lasers. The third-order nonlinear susceptibility is enhanced by tuning the laser frequencies 21 or 1+2 to a two-photon resonance. The wavelength of the generated coherent VUV radiation (with the frequency VUV=31, VUV=21+2 or VUV=1+2+3) is tunable in spectral regions between 133 and 217 nm. For most conversion processes an additional enhancement of the nonlinearity is provided by an autoionizing level or by a highly excited state close to E=VUV. With laser powers of 0.2–3 W the power of the generated sum frequencies is in the range of 5×105–6×1010 photons s–1 (0.5 pW–60 nW). 相似文献
7.
Coherent vacuum ultraviolet (VUV) radiation was generated by four-wave difference frequency mixing (VUV=21–2) of pulsed dye laser radiation in carbon monoxide (CO). The frequency 1 was tuned to the C
1+(=0)X
1+(=0) two-photon transition, while the dye laser frequency 2 was scaned around 17650 cm–1 which corresponds to the A
1(=7)«C
1+(=0) transition energy. The VUV intensity was found to be strongly wavelength dependent. The analysis of the spectrum revealed (i) that the VUV intensity was enhanced by the rotational levels of the A
1(=7) state and (ii) that the off-resonance excitation in the C
1+(=0)X
1+(=0) two-photon transition greatly contributed to the present four-wave mixing process. The effects of pumping laser detuning, saturation and foreign gases are briefly discussed. 相似文献
8.
C. E. Patton 《Czechoslovak Journal of Physics》1971,21(4-5):490-493
The relation between relaxation timeT, frequency swept resonance linewidth , and phenomenological damping is given by =2/T=(x+y), where
x,y
= (H
0+(N
x,y
–N
z
) 4M
s
).N
x,y,z
are sample demagnetizing factors,H
0 is the effectivez-directed static field, 4M
s
is the saturation induction, and is the gyromagnetic ratio. This fairly simple but general relation shows that the numerical relation between damping and relaxation at a given frequency can be quite different for in-plane and normally magnetized thin films. For thesame loss processes, so thatT
andT
are equal,
is larger than
. For permalloy films at 1 GHz,
=15
. In addition, the conventional field swept linewidth, H=/, is simply related to only forN
x
=N
y
. Both and H are geometry dependent and do not provide an intrinsic measure of the relaxation. These results are confirmed by both resonance and transient response experiments. The large values of for large angle switching may also be partially explained by this analysis because the relevant magnetization motion is due to a demagnetizing field normal to the film plane.Visiting scientist on leave fromRaytheon Company, U.S.A. Supported by the Japan Society for the Promotion of Science. 相似文献
9.
Using wave functions determined from ground-state local-density calculations, we have calculated the wave-dispersed free response of the optical nonlinear polarizability
(3)(–3;,,), for the C60 molecule and
(3)(–3;,,) i.e. Third-Harmonic Generation (THG) for films using a sum-over-states approach. The influence of screening was determined by applying an external static electric field in separate selfconsistent calculations to evaluate induced dipole moments which was used to determine the static linear and nonlinear polarizabilities. The polarizabilities calculated in the static limit were used to determine an effective screening parameter which was, in turn, used together with an RPA approach to calculate screened wave-dispersed, third-order nonlinear optical properties such as
(3)(–3;,,) and
(3)(–3;,,). Comparing evaluated polarizabilities with experimental values we found that the non-resonant free polarizability compares well in absolute magnitude with experimental results. Inclusion of screening results in a polarizability about two orders of magnitude below the experimental values.Paper presented at the 129th WE-Heraeus-Seminar on Surface Studies by Nonlinear Laser Spectroscopies, Kassel, Germany, May 30 to June 1, 1994 相似文献
10.
The nonlinear properties of a ferromagnet are studied. Many-time retarded Green's functions are used to obtain an expression for the cubic nonlinearity tensor with allowance for spatial dispersion of a uniaxial ferromagnet. The components due to the dipole-dipole interaction of the spins and also due to the anisotropy energy are found. A comparative analysis is made of the different components of the cubic nonlinearity tensor in both the nonresonance case and for various resonances, in particular when 0, 3 2w0, 2 0, 3 0 for the case in tripling of the frequency. Here, is the frequency of the incident wave and 0 is the frequency of uniform precession. It is shown that in the non-resonance case the largest components are those that are nonvanishing when no allowance is made for spatial dispersion; in the resonance cases the largest components are those due to the dipole-dipole interaction of the ferromagnetism spins.Translated from Izvestiya VUZ. Fizika, No. 12, pp. 53–58, December, 1973. 相似文献
11.
Nguyen Ai Viet 《Czechoslovak Journal of Physics》1981,31(3):269-274
In this paper the analytical expression is derived for the third-order optical harmonic coefficients x
abcd
v
(,,) of the atomic hydrogen at very low frequencies 0 in many level of the discrete energy spectrum.The author expresses his thank to Prof. Nguyen Van Hieu for suggesting the problem and fruitful discussions. 相似文献
12.
P. B. Podosenov 《Russian Physics Journal》1982,25(10):874-876
It is shown in this paper that the damping decrements of electromagnetic waves with right circular polarization and the decrements of plasma oscillations near the cyclotron and hybrid frequencies in a strong magnetic field eBpe are proportional to the square of the cyclotron frequencies eB and iB. In a weak magnetic field eBpe the damping decrements of all modes are proportional to the square of the plasma oscillation frequencies pe, pi. Taking account of ions results in a nonzero damping decrement for electromagnetic waves with left circular polarization.Deceased.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, p. 8–11, October, 1982.In conclusion, I am grateful to L. S. Kuz'menkov and P. Polyakov for constant attention to the research and for useful remarks. 相似文献
13.
We prove that the integrated density of states () for a potentialW
=V
per +V
has Lifshitz tails where Vper is a periodic potential with reflection symmetry andV
is a random potential, e.g., of the formV
=q
i
()f(x–i).research partially supported by DFG.research partially supported by USNSF under grant No. MCS-81-20833. 相似文献
14.
Orlin Stoytchev 《Letters in Mathematical Physics》1993,27(1):43-50
Every normal, faithful, self-adjoint functional on a von Neumann algebraA canonically determines a one-parameter-weakly continuous *-automorphism group
(the analog of the modular group) and a canonical 2 grading onA, commuting with
. We show that the functional satisfies the weak super-KMS property with respect to
and Furthermore, we prove that
and are the unique pair of a-weakly continuous one-parameter *-automorphism group and a grading of the algebra, commuting with each other, with respect to which is weakly super-KMS. The above results thus provide a complete extension of the theory of Tomita and Takesaki to the nonpositive case.Supported in part by the National Science Foundation under Grant DMS-8922002. 相似文献
15.
J.K. Baria 《Czechoslovak Journal of Physics》2002,52(8):969-989
A model pseudopotential depending on an effective core radius but otherwise parameter free is proposed to study the equation of state by incorporating the s-d hybridization effects. Very recently proposed screening function due to Sarkar et al has been used to obtain the screened form factor. The equations of state for Cu, Ta, Mo, W and Pt have been studied up to the pressure of 1000 GPa. The vibrational properties such as phonon dispersion curves (in q and r space), phonon density of states, mode Grüneisen parameters, maximum frequency max, mean frequency , 21/2 = (/ -1)1/2 and fundamental frequency 2 and static properties such as dynamical elastic constants of rhodium and iridium are also calculated. The theoretical results are compared with experimental findings wherever possible. A good agreement between theoretical investigations and experimental findings has confirmed our formulation. 相似文献
16.
We study time dependence of various measures of entanglement (covariance entanglement coefficient, purity entanglement coefficient, normalized distance coefficient, entropy coefficients) between resonantly coupled modes of the electromagnetic field in ideal cavities with oscillating boundaries. Two types of cavities are considered — a three-dimensional cavity possessing eigenfrequencies 3 = 31, whose wall oscillates at the frequency w = 21, and a one-dimensional (Fabry–Perot) cavity with an equidistant spectrum n = n1 where the distance between perfect mirrors oscillates at the frequencies 1 and 21. The behavior of entanglement measures in these cases turns out to be completely different, although all three coefficients demonstrate qualitatively similar time dependences in each case (except some specific situations where the covariance entanglement coefficient based on traces of covariance submatrices seems to be essentially more sensitive to entanglement than other measures, which are based on determinants of covariance submatrices). Different initial states of the field, namely, vacuum, squeezed vacuum, thermal, Fock, and even/odd coherent states, are considered. 相似文献
17.
The gravitational nonradiative collapse of dust configurations in the presence of electromagnetic field is analyzed in terms of exact dynamical solutions for a wide range of spacetime symmetries: cylindrical, pseudoplanar, toroidal, and also spherical, planar, and pseudospherical [when the anisotropy factor of the (x
2,x
3) surfaces,(R, T), is replaced by a massless scalar field]. The condition that the collapse is nonradiative leaves three possibilities for the coordinate dependence of(R,T) (i)=(a),a (R, T) being the scale factor of the (x
2,x
3) surfaces, (ii)=(T), and (iii)=(R). Almost all (in the meaning indicated in the text) solutions for charged dust with=(a) and for dust in the external electromagnetic field with=(T) and=(R) have been obtained and discussed. A wideranging discussion concerning the topics of papers I–III is given. Special attention is paid to the question of horizon existence and formation and also the perspective of extension of the techniques developed onto the more realistic case of axial symmetry. 相似文献
18.
In a high-power microwave-plasma system, it has been experimentally found that electromagnetic (em) radiation at subharmonic frequencies [specifically, (3/2)0 and (5/2)0] of the electron plasma frequency of the unperturbed state, 0, can be emanated from cavitons which are resonantly driven by an intense em pulse (frequency 0) in an unmagnetized inhomogeneous plasma. Electron oscillations at ~ (1/2)0 are preferentially excited inside a deep (|n/nc|0.5) caviton although this is not deep enough to resonantly support (1/2)0 oscillations. The experimental results show that the coupling between the (1/2)0 electron oscillations inside the caviton and the electron plasma waves at (3/2)0, which is originally excited due to the mode conversion of the incident microwave at the resonant layer and which generates the caviton, produces a localized nonlinear current which emits em waves at (3/2)0. A similar coupling between (3/2)0 and 0 frequencies can emit em waves at (5/2)0. The model to explain the above new phenomenon is discussed.Institute of Research and Development, and School of High Technology for Human Welfare, Tokai University, Japan. Department of Physics, University of California, Los Angeles, California. Published in Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 5, pp. 596–616, May, 1994. 相似文献
19.
A. A. Gogolin 《Zeitschrift für Physik B Condensed Matter》1985,58(3):205-211
The averaged retarded electron Green functionG
+(,k) in 1d disordered metal is calculated using the Berezinsky diagram technique. Using the Gorkov's theory it is shown, that the substitution of inG
+ (,k) by the square of the external frequency atk=0 gives the dependence of Fröhlich conductivity F(). This dependence describes the impurity pinning of CDW in 1d disordered metals. The good agreement of this dependence with experimental data Zeller et al. about F() in quasi-1d conductor KCP is found 相似文献
20.
The amplification of light signals (angular frequency S in some isotropic media (D2O, fused silica, and Schott type SF10 glasses) by noncollinear phase-matched parametric four-photon interaction 1+2S+1 is studied theoretically. Computer simulations are carried out for fundamental and second-harmonic pump pulses of a mode-locked Nd: glass laser. Degenerate interaction (wavelength 1=2=1054nm or 527 nm) and nondegenerate interaction (1=1054nm, 2=527 nm are considered. Characteristic phase-matching parameters and gain parameters versus wavelength are determined. Limitations by spectral bandwidth, optical absorption, optical damage, self-phase modulation, self-focusing and stimulated Raman scattering are analysed. 相似文献