Spectral study of light with a very low intensity by means of the measurement of laplace or fourier transform of the time-interval probability

In this work we intend the analysis of light with a very low intensity be means of the measurement of Laplace or Fourier transform of the probability of the time-intervals between two successive photons. The method is applied to the particular case of light of lorentzian spectrum and the error with which the spectral width would be obtained is studied (with a theoretical model and simulating through a computer). This error is confronted with that which might be attained if the spectral width were determined from the intensity correlation function. Results are discussed.     

双曲余弦-高斯光束经微小孔衍射的轴上光强特性

基于横截面上精确表述的光强和瑞利-索末菲衍射积分公式,通过数值计算分析双曲余弦-高斯光束经微小孔衍射的轴上光强特性,详细讨论了偏心参数、微小孔的孔径a和束腰宽度与波长之比w0/对双曲余弦-高斯光束轴上光强的影响。结果表明:双曲余弦-高斯光束的轴上光强分布依赖于偏心参数、孔径a、w0/参数和传输距离。     

Photorefractive amplification and generation of light beams in BaTiO3 controlled by the intensity of the pump light

3 by photorefractive forward four-wave mixing. The intensity of a signal beam is amplified by a factor up to 3000. We show that heating of the crystal by absorption of the pump light influences the gain because of the thermo-optic effect. Thus both, amplification and generation can be controlled by the intensities of the pump beams. Received: 23 January 1998     

On QCD sum rules of the Laplace transform type and light quark masses

We discuss the relation between the usual dispersion relation sum rules and the Laplace transform type sum rules in QCD. Two specific examples corresponding to the ?-coupling constant sum rule and the light quark masses sum rules are considered. An interpretation, within QCD, of Leutwyler's formula for the current algebra quark masses is also given.     

Determining the cutoff frequencies of weakly guiding optical fibres by the Laplace transform

We investigate the Laplace transform of the reduced radial Helmholtz equation for the electromagnetic fields in weakly guiding optical fibres. In the Laplace transform space we derive an integral condition for the cutoff frequencies of the LP modes. We apply our equation to several refractive index profiles of practical interest.     

Bragg diffraction of light beams by ultrasound with a curved wave front in gyrotropic cubic crystals

We have investigated Bragg diffraction of light beams by ultrasound in gyrotropic cubic crystals for strong acoustoopitc interaction. We have obtained analytical solutions of the vector-matrix coupled-wave equations in partial derivatives relative to the spatial distributions of the light beams and their angular spectra. We consider the asymptotic form of the solutions in different regimes and the diffraction efficiencies. We study the transformation of the amplitude and polarization distributions with respect to the angular spectrum of the diffracted radiation under strong-interaction conditions in the field of an ultrasonic beam with a curved wave front.Tomsk Institute of Automated Control Systems and Radioelectronics. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 3, pp. 273–288, March, 1994.     

Testing of the constrained regularization method of inverting Laplace transform on simulated very wide quasielastic light scattering autocorrelation functions

Provencher's constrained regularization method of inverting the Laplace transform was tested on 7 decades wide simulated quasielastic light scattering (QELS) data. The standard method with integration and logarithmic grid was shown to undersmooth seriously theG(Γ) distribution in the region of largeΓ (small relaxation timeτ). The regularization can be considerably improved by switching the integration off. Then, smooth distributions of relaxation timeτ of the generalized exponential type are reproduced essentially correctly with a tendency to replace asymmetric peaks by more symmetric ones with shoulders (in the Gaussian distribution ofτ) or side peaks (in the Gaussian distribution of 1/τ) on the slow decrease sides. In distributions with singularities such as edges of histogram bins or delta functions, the coarse shape of the distribution is recovered essentially correctly, but smoothing of singularities causes a distortion of wide regions of the relaxation spectrum usually in the form of sinusoidal waves. The bias introduced by taking the square root of theg ₂ function was shown to worsen sometimes the CONTIN results considerably. Thus, the use of Provencher's CONTIN program with logarithmic grid and integration switched off is recommended for the analysis of very wide QELS autocorrelation curves.     

Instantaneous intensity analysis of impulsive sound by the wavelet transform

The method for measuring instantaneous intensity by using the wavelet transform is proposed. We also conducted an analysis of the experimental data by using the hammering noise and confirmed the applicability of this calculation method.     

Creation evidence of the second non-dispersive Zakharenko wave by helium atomic beams in superfluid helium-II at low temperatures

In this work, the experimental results of the creation of the second non-dispersive Zakharenko wave (C _ph = C _g ≠ 0) in the negative roton branch (the so-called second sound) of the bulk elementary excitations (BEEs) energy spectra are introduced. Several BEE signals detected by a bolometer situated in the isotopically pure liquid helium-II at low temperatures ∼100 mK are shown, which give evidence of negative roton creation in the liquid by helium atomic beams striking the liquid surface. The negative roton signals were clearly distinguished by the following ways: the negative roton signal created by helium atomic beams appeared earlier than the positive roton signal created by the beams, and presence of both positive and negative roton signals together. It is natural that the negative roton creation by the beams requires the ⁴He-atom energies ∼12 K, while the positive roton creation by the atomic beams requires energies ∼35 K. Therefore, successive increase in the heater power resulting in an increase in the ⁴He-atom energies gives solid evidence that the negative rotons are first created in the liquid by the helium atomic beams.      

Parametric excitation of the drift wave by a modulated ion beam

Parametric excitation of the drift wave is observed by an ion beam modulated near the lower-hybrid frequency. An rf field parallel to the magnetic field is found to play an important role in the excitation of the instability. Substantial increase of the ion and electron temperatures is observed.     

Indirect measurement of the intensity of incident light by the light transmission fluctuation method

The light transmission fluctuation method is a simple and useful method for in situ and in-line measurement of particle size and concentration. To accomplish the measurement, it is necessary to know the intensity of incident light or background signal I(0). However, measuring I(0) during in-line applications is hard. In this Letter, an algorithm is proposed to indirectly measure I(0) based on the variation of transmitted light signals. Experiments have been carried out to verify the algorithm and the maximum deviation between premeasured I(0) and indirectly measured I(0)' is less than 2.5%.     

Exact solutions of the Klein—Gordon equation with ring-shaped oscillator potential by using the Laplace integral transform

We present exact solutions for the Klein-Gordon equation with a ring-shaped oscillator potential. The energy eigenvalues and the normalized wave functions are obtained for a particle in the presence of non-central oscillator potential. The angular functions are expressed in terms of the hypergeometric functions. The radial eigenfunctions have been obtained by using the Laplace integral transform. By means of the Laplace transform method, which is efficient and simple, the radial Klein-Gordon equation is reduced to a first-order differential equation.     

The light wave flow effect in a plane-parallel layer with a quasi-zero refractive index under the action of bounded light beams

It is shown that external optical radiation in the 450–1200 nm range can be efficiently transformed under the action of bounded light beams to a surface wave that propagates along the external and internal boundaries of a plane-parallel layer with a quasi-zero refractive index. Reflection regimes with complex and real angles of refraction in the layer are considered. The layer with a quasi-zero refractive index in this boundary problem is located on a highly reflective metal substrate; it is shown that the uniform low reflection of light is achieved in the wavelength range under study.     

Alternative to the hyperfine-change-collision interpretation for the behavior of magneto-optical-trap losses at low light intensity

Usually, the large trap loss rates observed in MOTs at the low light intensity regime have been associated with hyperfine change collisions (HCC). We propose an alternative mechanism to explain the sudden raise up of trap loss rates at low intensity without relying on HCC. Using the Gallagher-Pritchard model [Phys. Rev. Lett. 63, 957 (1989)] together with an intensity dependent escape velocity, we were able to reproduce qualitatively well some existing experimental results, including recent observations by Nesnidal et al. [Phys. Rev. A 62, 030701(R) (2000)]. This result reopens the discussion in order to better understand the physical mechanisms and their actual contribution to the trap losses.     

Superimposed volume holograms for measuring the phase and degree of mutual coherence of a light wave

Superimposed volume holograms, which make it possible to determine the phase and degree of mutual coherence of a stationary light wave consisting of partially coherent plane components incident on the holograms at different angles are proposed. To find these parameters of the light wave, the intensities of the waves reconstructed by the holograms are measured in the case of amplitude and phase modulation of the wave incident on the holograms. The phases and degrees of mutual coherence of the components of the wave incident on the holograms are found from the measured data. The holograms are studied based on the modal theory of superimposed volume holograms.     

Evaluation of surface kinetic data by the transform analysis of modulated molecular beam measurements

The merits of different modulated molecular beam detection systems are discussed and the application of modern data handling methods described. It is shown that by using time domain analysis together with fourier transform techniques, information on the kinetics of surface processes is obtained. Data at a number of excitation frequencies is obtained in a single experiment. A means of detecting non-linear surface processes, and an accurate method for the determination of reaction orders is given. The origin of spurious coherent signals is considered, and finally the application of the techniques is illustrated with data obtained from an investigation of the interaction of modulated As₄ beams with GaAs surfaces.     

On the possibility of measuring magnetic fields by scattered light

In the following paper we discuss the possibility of measuring magnetic fields by scattered light. In the case of uncorrelated electrons (i.e. α ?1) the electron spectrum is modulated with the electron gyration frequency if a certain condition is fulfilled. The essential parameters are discussed and some spectra are computed numerically.