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1.
The medium susceptibility related to stimulated Raman scattering (SRS) is known to be a complex value whose imaginary part
determines the SRS gain coefficient whereas the real part constitutes a small fraction of the refractive index at the frequencies
of the scattered emission that is proportional to the intensity of the exciting beam. Strong transverse nonuniformity of this
beam causes focusing of high-frequency components of the scattered light and defocusing of low-frequency ones that inevitably
affect their amplification efficiency. The effect for Gaussian pumping is responsible for a slight shift of the SRS gain spectrum
towards higher frequencies. The present work analyzes theoretically SRS excited by a Bessel light beam and demonstrates that
the axial component of the scattered emission experiences a frequency shift that is much greater than that for the case of
Gaussian beam pumping.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 3, pp. 336–341, May–June, 2008. 相似文献
2.
尝试用Woods-Saxon形式的光学势来分析K原子,通过拟合一系列K原子数据,得到了一套最佳光学势参数. 把得到的这套光学势和前人的其它几种光学势在接近核表面处作了比较,发现他们彼此符合得很好. 另外,与核子-核势相比较,对于虚部势,K-核的Woods-Saxon势与核子-核的很相似,但是对于实部,K-核势要更深更窄一些. 相似文献
3.
We consider aspects of the interaction between a V-type three-level quantum system and the bichromatic field of two waves,
one of which is assumed to be weak. We trace the dynamics of splitting into individual components for the spectral contours
of the absorption coefficient (gain) for the signal wave. We discuss the effect of amplification of the signal wave for its
frequency-degenerate two-wave interaction with pumping, when the field frequency is tuned to the “zero dispersion” point.
We determine the conditions with respect to the concentration of resonant atoms and the spectral regions of the frequencies
of the interacting waves for which, in order to correctly describe the effects under consideration, we need to take into account
the effect of pumping and the signal in both dipole-allowed transitions of an ensemble of V type three-level quantum systems.
We present the results of numerical calculations of the imaginary and real parts of the susceptibility of the resonant medium
at the frequency of the signal wave, as a function of the parameters for the high-power radiation and resonant transitions
of the quantum V system.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 631–636, September–October, 2007. 相似文献
4.
Laser induced third-order nonlinear optical responses of Brilliant Green solution (which belongs to triphenylmethane organic
dye group) was investigated by utilizing single beam Z-scan technique using a continuous wave He-Ne laser at the wavelength
of 632.8 nm. It was observed that the material exhibits self-defocusing and saturation absorption type optical nonlinearity
behavior. The measurements of the real and imaginary parts of the third-order nonlinear optical susceptibility were carried
out at several incident laser irradiations and different dye concentrations. It was found that the increase in any of the
incident laser intensity or solution concentration leads to the linear increase of the nonlinear refractive index. The obtained
values of the third-order nonlinearities of Brilliant Green solutions are amongst the highest reported CW regimes, to the
best of our knowledge. This study shows a great potential of the Brilliant Green for the application in nonlinear optical
devices. 相似文献
5.
F. Bassani V. Lucarini 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(3):323-330
The nonlinear oscillator model is useful to basically understand the most important properties of nonlinear optical processes.
It has been shown to give the correct asymptotic behaviour and to provide the general features of harmonic generation to all
orders, in particular dispersion relations and sum rules. We investigate the properties of pump and probe processes using
this model, and study those cases where general theorems based on the holomorphic character of the Kubo response functions
cannot be applied. We show that it is possible to derive new sum rules and new Kramers-Kr?nig relations for the two lowest
moments of the real and of the imaginary part of the third order susceptibility and that new specific contributions become
relevant as the intensity of the probe increases. Since the analytic properties of the susceptibility functions depend only
upon the time causality of the system we are confident that these results are not model dependent and therefore have a general
validity, provided one substitutes for the equilibrium values of the potential derivatives the density matrix expectation
values of the corresponding operators.
Received 25 January 1999 and Received in final form 26 April 1999 相似文献
6.
采用基于第一性原理的密度泛函理论平面波超软赝势方法计算了 1/4ML Cs原子吸附 (2 × 2) GaN(0001) 表面的吸附能、能带结构、电子态密度、电荷布居数、功函数和光学性质. 计算发现, 1/4ML Cs 原子在 GaN(0001) 表面最稳定吸附位为 N 桥位, 吸附后表面仍呈现为金属导电特性, Cs原子吸附GaN(0001)表面后主要与表面 Ga 原子发生作用, Cs6s 态电子向最表面 Ga 原子转移, 引起表面功函数下降. 研究光学性质发现, Cs 原子吸附 GaN(0001) 表面后, 介电函数虚部、吸收谱、反射谱向低能方向移动. 相似文献
7.
CHENGQing-Hua CAOLi WANGJun WUDa-Jin 《理论物理通讯》2004,42(4):553-556
We present an analytic investigation of the signal-to-noise ratio (SNR) by studying a signal modulated model of a single-mode laser system driven by pump noise and quantum noise with correlated real and imaginary parts,and find there is a maximum in the curve of the dependence of SNR upon the cross-correlation coefficient λq between the real part and the imaginary part, i.e., stochastic resonance appears in the SNR vs. λq curve. Moreover, when the SNR is at the maximum, the cross-correlation coefficient λq = O, which is coincidentally at the minimum of the mean normalized intensity fluctuation. The influences on stochastic resonance by the intensities of the pump and the quantum noise, the amplitude of the modulation signal, and the net gain of the laser are also studied. Furthermore, in order to ensure that the results obtained in this paper is reliable, the valid range for the linear approximation method is discussed. 相似文献
8.
Gordana Školnik 《Optics Communications》2009,282(7):1326-4184
We investigated the optical pumping of the Zeeman components of rubidium atoms, in the presence of the external magnetic field ranging from the geomagnetic up to 130 Gauss. Using the saturated absorption spectroscopy with linearly polarized pump and probe laser beams, the rubidium Doppler-free spectra at different magnetic field strengths were measured. The dips (negative intensity signals) in the saturated absorption spectra of the 87Rb hyperfine transition lines were observed. They come as a result of the alignment process induced by the incoherent population transfer due to the hyperfine optical pumping. By inspection of the dips for different magnetic field strengths we were able to conclude about the dynamics of the alignment process in the external magnetic field. Present work is a part of the investigations concerning the influence of the magnetic field on the velocity selective optical pumping of the rubidium atoms induced by femtosecond frequency comb [D. Aumiler, T. Ban, H. Skenderovi?, G. Pichler, Phys. Rev. Lett. 95 (2005) 233001; T. Ban, D. Aumiler, H. Skenderovi?, G. Pichler, Phys. Rev. A 73 (2006) 043407]. 相似文献
9.
Christophe Verhaege Valery Shcherbakov Pascal Personne 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(14):2338-2348
On the base of a lookup table approach we performed sensitivity tests of dual-polarization polar nephelometer (D2PN) data to optical and microphysical parameters of ensembles of spherical particles. Measurement errors were modeled as Gaussian random variables. It is shown that D2PN data enable to retrieve some microphysical parameters (depending on the case) along with the assessment of the complex refractive index. In the case of the low absorbing particles, measurement errors substantially reduce the sensitivity to the imaginary part of the refractive index and only the range of the imaginary part can be estimated, whereas the real part of the refractive index and the microphysical parameters can be retrieved. When the absorption of spherical particles is moderate, i.e., 10−4?χ?0.5, the real n and imaginary χ parts of the refractive index can be deduced along with the microphysical parameters. In the case when the absorption of spherical particles is high, only the microphysical characteristics and the imaginary part can be retrieved. These limitations on retrieval should be valid for data of other instruments measuring the same magnitudes as D2PN with the same errors, at least for aerosols made of spherical particles. 相似文献
10.
Richard Friedberg 《Physics letters. A》2010,374(34):3389-3395
We explore steady states of an open, no end-mirrors, low-Q cw laser pumped above the threshold for laser oscillations. We find that the spatial field profile of the steady state just above the threshold is the same as that of the eigenmode that dominates superradiance in the late linear regime from an initially inverted state without continued pumping. The threshold pumping rate and emission frequency are related to the real and imaginary parts of the eigenvalue of this dominant mode. 相似文献
11.
V. šachl 《Czechoslovak Journal of Physics》1963,13(11):792-799
With the help of the dispersion relation inequalities are derived as criteria for determining the imaginary part of the spectral function (scattering amplitude, dielectric constant, ...) in the finite interval with a chosen upper limit, on the assumption that the real part of the analytic function at a single point is known.The applicability for measurements of the elastic processes of strong interactions is discussed and with the help of criteria calculations for the imaginary part of the dielectric constant of lead selenide in an experimentally inaccessible region are carried out. 相似文献
12.
Effects of correlations between the real and imaginary parts of quantum noise on intensity fluctuation for a saturation laser model 下载免费PDF全文
This paper studies the effects of cross-correlations between the
real and imaginary parts of quantum noise on the laser intensity in
a saturation laser model. It derives the analytic expressions of the
intensity correlation function ${C(\tau)}$ and the associated
relaxation time ${T({C})}$ in the case of a stable locked phase
resulting from the cross-correlation ${\lambda_q}$ between the real
and imaginary parts of quantum noise. Based on numerical
computations it finds that the presence of cross correlations
between the real and imaginary parts of quantum noise slow down the
decay of intensity fluctuation, i.e., it causes the increase of
intensity fluctuation. 相似文献
13.
We report the experimental results of frequency-selective laser optical pumping and spin exchange of Cs with129Xe and131Xe in a high magnetic field of 11.74 T. Our results show that hyperpolarized129Xe and131Xe nuclear magnetic resonance (NMR) signals exhibit alternating phases when the laser frequency for pumping the cesium atoms is changed, which is explained on the basis of the high-field optical pumping of Cs. We obtain about 3% polarization of the129Xe. The electron-spin polarization of the Cs atoms has been measured to be about 22% with a simple NMR method. 相似文献
14.
We have studied the band structure and optical properties of 4H-SiC by using a full potential linearized augmented plane waves (FPLAPW) method. The density of states (DOS) and band structure are presented. The imaginary part of the dielectric function has been obtained directly from the band structure calculation. With band gap correction, the real part of the dielectric function has been derived from the imaginary part by the Kramers-Kronig (KK) dispersion relationship. The values of reflectivity for normal incidence as a function of photon energy have also been calculated. We found the theoretical results are in good agreement with the experimental data. 相似文献
15.
16.
As an optically pumped device, the lasing characteristics of a spherical microcavity laser depend on the optical pumping processes. These characteristics can be described in term of the Q factor and the optical field distribution in a microsphere. We derived analytical expressions and carried out numerical calculation for Q factor and optical field. The Q factor is found to be oscillatory functions of the radius of a microsphere and the pumping wavelength, and the pumping efficiency for a resonating microsphere is much higher than that for an anti-resonating microsphere. Using tunable lasers as pumping sources is suggested in order to achieve a higher pumping efficiency. Numerical calculation on optical field distribution in spherical microcavities shows that a well focused Gaussian beam is a suitable incident wave for cavity quantum electrodynamics experiments in which strong confinement of optical field in the center of a microsphere is requested, but higher order spherical wave should be used instead for exciting whispering-gallery-mode (WGM) microsphere lasers, for the purpose of favoring optical energy transferring to WGM in optical microspheres. 相似文献
17.
Keefe CD 《Journal of Molecular Spectroscopy》2001,205(2):261-268
The Kramers-Kronig transformation has been extensively applied in optical spectroscopy to calculate the real component of an optical quantity from the imaginary component, such as the real refractive index from the imaginary component, or vice versa. In this paper, the traditional proof of the Kramers-Kronig transformation, and its application to the complex refractive index, complex dielectric constant, and complex molar polarizability, are reviewed. Often the imaginary components of these quantities are fitted with standard lineshapes such as the Gaussian, Lorentzian, or Classical Damped Harmonic Oscillator (CDHO) lineshapes. It is shown that the usual Gaussian and Lorentzian lineshapes do not meet the physical criteria of these imaginary components nor the conditions of the Kramers-Kronig transformation since they are not odd functions of wavenumber. However, the CDHO lineshape meets the physical criteria of the imaginary components of these optical quantities and the Kramers-Kronig transformation. Modifications are presented that make the Gaussian and Lorentzian odd. The Gaussian decays so fast that the modification is not needed in practice; however, the Lorentzian is much slower to decay and thus modification is necessary whenever fitting peaks below approximately 250 cm(-1). Since the computational difference between the usual Lorentzian and modified Lorentzian is negligible, the author recommends that only the modified Lorentzian be used when fitting bands with a Lorentzian lineshape. Copyright 2001 Academic Press. 相似文献
18.
Einstein——Podolsky——Rosen entanglement in time-dependent periodic pumping non-degenerate optical parametric amplifier 下载免费PDF全文
The solution of the time-dependent periodic pumping non-degenerate
optical parametric amplifier (NOPA) is derived when the pump
depletion is considered both above and below thresholds. Based on
this solution, the quantum fluctuation calculated shows that a high
entanglement and a good squeezing degree of the parametric light
beams are achieved near and above thresholds. We adopt two kinds of
pump fields: (i) a continuously modulated pump with a sinusoidal
envelope; (ii) a sequence of laser pulses with Gaussian envelopes.
We analyse the time evolution of continuous variable entanglement by
analytical and numerical calculations, and show that the periodic
driven pumping also improves the degree of entanglement. The
squeezing and Einstein-Podolsky-Rosen (EPR) entanglement by using
the two pumping driven functions are investigated from below to
above the threshold regions, the tendencies are nearly the same, and the
Gaussian driven function is superior to that of the sine driven function,
when the maximum squeezing and the minimum variance of
quantum fluctuation are considered. In the meantime, the
generalization of frequency degenerate OPA to frequency
non-degenerated OPA problem is investigated. 相似文献
19.
The real time finite temperature perturbation is carried out for the imaginary part of gluon self-energy in the general covariant gauge. Using the result we obtain the electric susceptibility and the magnetic permeability. We show that their imaginary part has a correct sign in the space-like momentum region and hence the finite temperature perturbation in QCD is meaningful, contrary to the assertion due to Hansson and Zahed based on the analysis in the time-like momentum region only. 相似文献
20.
Effects of correlations between the real and imaginary parts of quantum noise on intensity fluctuation for a saturation laser model 下载免费PDF全文
This paper studies the effects of cross-correlations between the real and imaginary parts of quantum noise on the laser intensity in a saturation laser model. It derives the analytic expressions of the intensity correlation function C(τ) and the associated relaxation time T(C) in the case of a stable locked phase resulting from the cross-correlation λq between the real and imaginary parts of quantum noise. Based on numerical computations it finds that the presence of cross correlations between the real and imaginary parts of quantum noise slow down the decay of intensity fluctuation, i.e., it causes the increase of intensity fluctuation. 相似文献