Physical optics

About: Physical optics is a research topic. Over the lifetime, 5342 publications have been published within this topic receiving 101388 citations. The topic is also known as: wave optics.

A new method in inverse scattering based on the topological derivative

Abstract: The problem of imaging objects embedded in a transparent homogeneous medium is considered. It is assumed that the wavelength of the probing radiation is finite so that scattering effects need to be taken into consideration in the reconstruction process. This problem is commonly referred to as 'inverse scattering' in the literature. Many algorithms, including backpropagation-based algorithms, attempt to solve this imaging problem in either of two ways: (1) by assuming linearizing approximations such as the Born, Rytov or physical optics approximations which result in closed-form expressions for the inversion formula; or (2) by solving the nonlinear inverse scattering problem using an iterative algorithm, which is computationally more expensive. In this paper, a new method for inverse scattering is proposed. This method is based on the notion of the 'optimal topology' that solves the inverse scattering problem. To find this optimal topology, a function called the topological derivative is defined. This function quantifies the sensitivity of the scattered field to the introduction of a small scatterer at a point in the domain. Based on this definition, and the heuristic that the boundary of the objects can be considered as a group of point scatterers, we will identify high values of this function with the location of these boundaries. It is shown that the topological derivative can be calculated analytically so, as a result, the proposed reconstruction algorithm is not iterative. In addition, no approximations (such as the Born, Rytov or physical optics approximations) to the wavefield are made. The numerical examples shown in this paper demonstrate that this simple and efficient heuristic scheme can be used to accurately reconstruct the shape of scatterers.

Optical channels : fibers, clouds, water, and the atmosphere

Abstract: 1. Introduction.- 2. Coherence Theory and Random Channels.- 3. Optical Receivers.- 4. The Fiber Optic Channel.- 5. The Turbulence Channel.- 6. The Optical Scatter Channel and Its Properties.- 7. Mathematical Models for Energy Propagation in the Optical Scatter Channel.- Appendix A. Generalized Radiometry.- A.1. The Generalized Radiance.- A.2. The Mutual Radiance.- A.3. The Generalized Radiant Emittance.- A.4. The Generalized Radiant Intensity.- References.- Appendix B. Transport Theory.- B.1. Heuristic Derivation of the Radiative Transport Equation.- B.2. Radiative Transfer Theory in the Small-Angle Scattering Limit.- B.3. Derivation of the Small-Angle Transport Equation from Parabolic Wave Optics Theory.- Appendix C. Solution of the Small-Angle Transport Equation for the Generalized Radiance and the Mutual Coherence Function.- Appendix D. Power Flow in Fibers.- Appendix E. Optical and Physical Thickness Relations for Clouds at Various Locations on the Earth.- Appendix F. Atmospheric Optical Loss Model.

I: The Wigner Distribution Function in Optics and Optoelectronics

Abstract: Publisher Summary The Wigner distribution function (WDF) in quantum mechanics is a mathematical tool that correctly yields the expectation values of any function of the coordinates or the momenta. The chapter discusses WDF applications to the characterization of light fields and optical systems and to the problem of coupling optimization between sources and waveguides. Phenomena such as diffraction, interference, coherence, or polarization cannot be managed in the framework of geometrical optics but only within wave optics, where the light field is characterized by a vectorial distribution that satisfies the Helmholtz equation. The applications of the WDF support the assertion that the WDF is a valuable theoretical and experimental tool in optics and optoelectronics. Further expansion of WDF applications will probably result from the recent extension of the WDF definition as a quantum quasiprobability distribution of number and phase and as a wide-band distribution function in signal processing.

Observation of geometric phases for mixed states using NMR interferometry.

Abstract: Examples of geometric phases abound in many areas of physics. They offer both fundamental insights into many physical phenomena and lead to interesting practical implementations. One of them, as indicated recently, might be an inherently fault-tolerant quantum computation. This, however, requires one to deal with geometric phases in the presence of noise and interactions between different physical subsystems. Despite the wealth of literature on the subject of geometric phases very little is known about this very important case. Here we report the first experimental study of geometric phases for mixed quantum states. We show how different they are from the well-understood, noiseless, pure-state case.