Phase Of Wave Field Research Articles

Wave-field phase singularities: near-neighbor correlations and anticorrelations

Near-neighbor phase singularities (vortices) in a random Gaussian wave field are shown to be extensively correlated or anticorrelated depending on the vortex parameter under consideration. In some instances these correlations extend out even to fourth-nearest neighbors. The correlations reflect an underlying, recently discovered universal sign principle and can be expected to be an important feature of all wave fields.

Scanning tunneling microscopy of RF oscillating surfaces

AbstractAmplitude and phase of high frequency surface acoustic wave (SAW) fields are investigated by a novel scanning tunneling microscopy technique. The gap voltage is modulated at a slightly detuned high frequency. Due to the nonlinearity of the tunneling process a frequency mixing appears. For scanned areas with dimensions much smaller than the wavelength of the SAW a remarkable local variation of amplitude and phase of the tunneling current at the difference frequency is observed. Depending on the local morphology different components of the particle displacement vector are detected. Model calculations of amplitude and phase images are presented for a real topography.

One‐way wave propagation methods in direct and inverse scalar wave propagation modeling

Wave field splitting, invariant imbedding, and phase space methods reformulate the Helmholtz wave propagation problem in terms of an operator scattering matrix characteristic of the modeled environment. The subsequent equations for the reflection and transmission operators are of first‐order (one‐way) in range, nonlinear (Riccati‐like), and, in general, nonlocal. The reflection and transmission operator equations provide the framework for constructing inverse algorithms based on, in principle, exact solution methods.

Correlation characteristics of waves in lossy media with smooth fluctuations of the refractive index with oblique incidence on boundary

Abstract The features of coherence function (and angular spectrum) and also the fluctuation of amplitude and phase of wavefield in a random strongly absorptive medium are investigated in the case of arbitrary angle of incidence at the surface. In this paper it is elucidated that with oblique incidence a dissipation in the random medium can accelerate the accumulation of wave fluctuations and its incoherence. This effect strongly depends on the rate of decrease of the ‘wings’ of the scattering indicatrix. An analytical theory (Rytov's approximation and modified method of parabolic equation) has been modelled by Monte Carlo simulation of wave propagation, and also by numerical solution of the model transfer equation. It is revealed that the width of an angle spectrum can nonmonotonically change with the immersion to the absorptive medium.

Wave field splitting, invariant imbedding, and phase space analysis applied to ocean acoustic wave propagation modeling.

Due to the extremely large size of realistic three-dimensional ocean problems, there is an understandable desire to incorporate marching methods into the solution algorithm for the inherently elliptic (frequency-domain) problem. Recognizing that typical ocean propagation problems are essentially scattering problems in terms of a transition region and transversely inhomogeneous asymptotic half-spaces, wave field splitting, invariant imbedding, and phase space methods reformulate the problem in terms of an operator scattering matrix characteristic of the transition region. The subsequent equations for the reflection and transmission operators are first order in range, nonlinear (Riccati-like), and, in general, nonlocal. The system is well-posed, but stiff. The reflected and transmitted wave fields can be computed in a very efficient manner, while the wave field in the transition region (if desired) can be computed by essentially a layer-stripping algorithm. In principle, the transition region can be divided into subregions, allowing for parallel computations and subsequent recombination. Numerical examples will be discussed. [Work supported by NSF, AFOSR, ONR, ASEE, JEWC.]