Showing papers on "Physical optics published in 1982"

Integrated optics, theory and technology

Abstract: Integrated Optics explains the subject of optoelectronic devices and their use in integrated optics and fiber optic systems The approach taken is to emphasize the physics of how devices work and how they can be (and have been) used in various applications as the field of optoelectronics has progressed from microphotonics to nanophotonics Illustrations and references from technical journals have been used to demonstrate the relevance of the theory to currently important topics in industry By reading this book, scientists, engineers, students and engineering managers can obtain an overall view of the theory and the most recent technology in Integrated Optics

Depolarization of electromagnetic waves scattered from slightly rough random surfaces: a study by means of the extinction theorem

Abstract: The scattering and depolarization of electromagnetic waves from perfectly conductive slightly rough random surfaces is studied using the small perturbation method through the Ewald–Oseen extinction theorem. This permits predictions in those cases in which the physical optics, or the Kirchhoff approximation, fails, namely, at grazing incidence and when the wavelength of the incident radiation is comparable with the correlation length of the random heights. In this way it is seen, for example, that, as with the Rayleigh–Fano method, the depolarization of the fields is obtained from the second order of the expansion and exists even in the backscattering and specular directions. Also, unlike the predictions of the Kirchhoff approximation, this depolarization depends on the surface shape. However, this approach yields in the specular direction the same result as the Kirchhoff approximation for those cases in which the latter is known to be valid, i.e., for large correlation lengths and non-grazing-incidence directions and establishes precise conditions under which the Kirchhoff approximation is retrieved in the backscattering direction.

Light and Color

Abstract: The Physical Nature of Light. The Origin of Color. Colorimetry -- Describing and Measuring Color. Color Vision. The Appearance of Objects. Geometric Optics. Applied Geometrical Optics. Wave Optics. Light and Color in Nature. Appendixes.

Path-integral approach to problems in quantum optics

Abstract: A formalism for applying path integrals to certain problems in nonlinear optics is considered. The properties of a coherent-state propagator are discussed and a path-integral representation for the propagator is presented. This representation is then employed in evaluating the propagator for general single-mode and multimode Hamiltonians which are at most quadratic in the creation and destruction operators of the field. Some examples involving parametric processes are given.

Secondary pattern and focal region distribution of reflector antennas under wide-angle scanning

Abstract: A new numerical method, Fourier-Bessel series techniques, has been developed to investigate the far-field pattern and focal region distribution of reflector antennas under wide-angle scanning. In this Fourier-Bessel series technique, the current on the reflector surface is first expanded in terms of elementary sinusoidal functions via the well established fast Fourier transform (FFT) algorithm and the surface integration involved in physical optics integration is then carried out analytically. The derivation of Fourier-Bessel series and its convergence as applied to parabolic reflectors are described. The secondary patterns and focal region distributions of a parabolic reflector with F/D = 0.48 and scanning up to 48 beamwidths are presented.

Nonconventional optical systems and the brightness theorem.

Abstract: The brightness on radiance theorem in geometrical optics is reviewed and restated according to the laws of physics. (AIP)

A hybrid diffraction technique--General theory and applications

Abstract: A new method is presented for calculating the current on a perfectly conducting body. The starting point of the method is in the assumption that the dominant current on the scattering body is an optics type current close to 2\hat{n} \times \bar{H}^{i} . Near shadow boundaries, the current is represented by the moment method such that the total current in the vicinity of a shadow boundary is the sum of the optics current and the moment method current. (In this sense the method may be equivalent to the physical theory of diffraction.) The magnetic field integral equation is then used in an iterative procedure to obtain the correct current in the asymptotic regions (away from shadow boundaries) and in the moment method region. Because the iterative process starts with a current close to the true current, convergence is rapid with two or three iterations being typical. The general theory is presented and then applied to the infinite wedge problem and to the problem of a two-dimensional square cylinder. Results are compared with other independent solutions, and excellent agreement is demonstrated. A comparison is made with conventional physical optics. Application of the hybrid diffraction method to curved surfaces is discussed. Advantages and disadvantages of the method are also discussed.

Light scattering in the physical optics approximation; application to large spheroids

Abstract: The field radiated everywhere in space may be expressed by means of an integral, in terms of the surface field over a closed surface S. S being the surface of a regular shaped scatterer, that unknown surface field has been evaluated by using the Physical Optics Approximation. The method requires the use of Fresnel's and Snell's laws for plane waves which may be inhomogeneous since the scatterer may have a complex refractive index. Accounting for the finite curvature of the scatterer, the amplitude and phase of the waves inside the scatterer have been calculated. A program which allows the computation of the usual four components of the scattered light has been implemented, checked in various particular situations and been successfully used in the case of a spheroidal scatterer at nose-on incidence.

Gravitational effects on the polarization plane

Abstract: We study the rotation of the polarization plane of an electromagnetic wave due to a gravitational field. An evolution law for the polarization plane is derived in the geometric optics approximation. For the particular case of a Kerr space-time, we obtain the polarization plane rotation for an incident light ray parallel to the Z axis at z = -∞ and for a radially outgoing one. The results are compared with others which have already appeared in the literature.

GTD Terrain Reflection Model Applied to ILS Glide Scope

Abstract: The capability of calculating the reflection of electromagnetic signals from uneven terrain has many applications. One of these is the determination of instrument landing system (ILS) glide slope performance. For this application the wavelength is approximately 1 m, incidence angles are usually near grazing, and the fields are horizontally polarized, so that gross irregularities such as dropoffs and hills are more important than surface roughness. Past approaches used to calculate the ground reflections for this application have been three-dimensional physical optics models which were very cumbersome and time consuming and which neglected important diffraction and shadowing phenomenon; a two-dimensional physical optics model which was faster than the three-dimensional models but ignored many shadowing and transverse terrain variation effects; and a half-plane diffraction model which is applicable only to a specified type of terrain geometry. In this paper a terrain reflection model based on the geometrical theory of diffraction (GTD) is described which can accommodate any piecewise linear terrain profile, requires less computer time than the physical optics models, is capable of including transverse terrain effects, and determines the reflected fields with all important diffraction and blockage effects included.

Efficiency of nonimaging concentrators in the physical-optics model

Abstract: The consequences of Liouville’s theorem that are known to be valid in the geometrical-optics limit are shown to hold when wavelength-dependent effects, for example, diffraction and scattering, are taken into account.

On the Calculation of Intensity in Dispersive Inhomogenous Media in the Ray Approximation

Abstract: The Hamilton-like equations of geometrical optics determine the rays of the relevant wavefield in the short wavelength limit. It is shown that, by appending a set of subsidiary equations, the associate intensity can be computed along each ray, as the ray itself is traced. The analysis is applicable to any form of wave propagation, and is not confined to optics. It extends to a fully dispersive anisotropic system, some work of P. Ugincius J. acoust. Soc. Am. 45, 193-205, 206-209 (1969) on acoustic propagation (which is not dispersive) in inhomogeneous media.

Scattering and depolarization by rough surfaces near grazing angles--Full wave solutions

Abstract: Using the full wave approach to rough surface scattering, the apparent singularity in the physical optics and perturbation expressions for the scattered fields is not encountered. The full wave expression for the far fields is shown to vanish in a continuous manner as the observer moves across a shadow boundary. Precise criteria are given for near grazing angles where uniform plane wave excitations cannot be assumed. Comparisons are made between the full wave and the physical optics and perturbation solutions. Since the full wave solution is shown to bridge the gap between the physical optics and perturbation solutions, it accounts for both specular and Bragg scattering. The full wave solutions satisfy reciprocity, duality, and realizability relationships in electromagnetic theory, and they are invariant to coordinate transformations.

Operator Methods In Physical Optics

Abstract: This paper contains a treatment of paraxial wave optics which is expressed in terms of operators acting on vectors in an abstract space. The abstract vectors represent the electromagnetic field (in scalar approximation). The effects of propagation, reflection, and refraction, etc., are implemented by operators acting on the abstract field vectors. This leads to an operator algebraic formulation of paraxial wave optics.© (1982) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A hybrid MM-geometrical optics technique for the treatment of wire antennas mounted on a curved surface

Abstract: The method of moments (MM) and geometrical optics (GO) can be formally combined into a hybrid MM-GO technique. Wire-type antennas are treated by the method of moments, and their interaction with a large curved surface is accounted for through geometrical optics. Thus, in this communication, geometrical optics is used to account for the interaction of a monopole antenna with the curved surface on which it is mounted. Two hybrid MM-GO technique formulations for doing this are discussed. Results are shown for the impedance of a monopole on a circular cylinder as the radius of the cylinder is varied. Some of these results are compared with experimental measurements and good agreement is shown between the calculated and measured results.

Comparison of σ o Obtained from the Conventional Definition with σ o Appearing in the Radar Equation for Randomly Rough Surfaces

Abstract: A comparison is made of the radar cross section of rough surfaces calculated in one case from the conventional definition and obtained in the second case directly from the radar equation. The objective of the analysis is to determine how well the conventional definition represents the cross section appearing in the radar equation. The analysis is executed in the special case of perfectly conducting, randomly corrugated surfaces in the physical optics limit. The radar equation is obtained by solving for the radiation scattered from an arbitrary source back to a colocated antenna. The signal out of the receiving antenna is computed from this solution and the result put into a form recognizeable as the radar equation. The conventional definition is obtained by solving a similar problem but for backscatter from an incident plane wave. It is shown that these two forms for ?' are the same if the observer is far enough from the surface; However, the usual far-field criteria are not sufficient. For the two cross sections to be the same, the observer must be far from the surface compared to the radii of curvature of the surface at the reflection (specular) points. Numerical comparison of the two cross sections has been made for normally distributed surfaces and the difference can be significant.

Several Maggi-Rubinowicz representations of the electric field

Abstract: The Maggi-Rubinowicz technique for scalar and vector fields can be interpreted as a transformation of an integral over an open surface to a line integral around the rim and geometrical optics terms. Using this transformation, Maggi-Rubinowicz analogues are obtained for several integral representations of the electric field. In the case of diffraction from a circular aperture, numerical comparisons between a physical optics and the corresponding Maggi-Rubinowicz formulation show the methods to be in good agreement. To circumvent certain convergence difficulties in the Maggi-Rubinowicz solution that occur as the observer approaches the shadow boundary, a variable mesh integration is used. For the examples considered, where the ratio of the aperture diameter to wavelength is about ten, the Maggi-Rubinowicz formulation yields a significant decrease in computation time relative to the physical optics formulation.

Upper bound on the efficiency of certain nonimaging concentrators in the physical-optics model

Abstract: A simple treatment by scalar-wave theory yields upper bounds to the efficiency of nonimaging concentrators that are lower than those given by geometrical optics.

Scattering cross sections for composite surfaces with large mean square slopes—full wave analysis

Abstract: In this work the full wave approach to rough surface scattering is applied to composite models of rough surfaces with large mean square slopes. It is shown that both specular point scattering as well as Bragg scattering are accounted for in the analysis and the results are compared with earlier solutions based on a combination of physical optics and perturbation theories. Using the full wave approach it is not essential to decompose the rough surface into individual surfaces with different roughness scales unless it is desired to separate the specular point contribution from the Bragg contribution to the scattering cross sections. Shadowing is accounted for in the analysis.

Improved ray representation for planar optical waveguides

Abstract: Scalar wave optics of planar optical waveguides is converted into an exact ray description by nonlinear mapping relations which map ray functions into mode functions and vice versa. An exact duality invariant is derived and shown to be closely related to the Lewis invariant. The theory is also shown to reduce to geometric optics in the limit of vanishing wavelength.

Scattering from a random layer of leaves in the physical optics limit

Abstract: Backscatter of electromagnetic radiation from a layer of vegetation over flat lossy ground has been studied in collaborative research at the George Washingnton University and the Goddard Space Flight Center. In this work the vegetation is composed of leaves which are modeled by a random collection of lossy dielectric disks. Backscattering coefficients for the vegetation layer have been calculated in the case of disks whose diameter is large compared to wavelength. These backscattering coefficients are obtained in terms of the scattering amplitude of an individual disk by employing the distorted Born procedure. The scattering amplitude for a disk which is large compared to wavelength is then found by physical optic techniques. Computed results are interpreted in terms of dominant reflected and transmitted contributions from the disks and ground.

Coherence Theory And Caustic Corrections

Abstract: Recent studies in underwater acoustics have shown how coherence theory may be used to determine the correct intensity distribution in the neighborhood of caustics. These studies may be of interest to the optics community and we review here the method developed. We begin with the basic equation governing the coherence function in the parabolic approximation. The radiation propagates in a medium with a variable mean index of refraction. A lowest order approximation to the basic equation yields the geometric optics solution. To next order we use a two-scale expansion to include the correction term to the geometric optics calculation. This gives the correct intensity distribution in the neighborhood of caustics and it is shown that in the limit of a point source the results reduce to those obtained previously. The results of a numerical example are given. Finally it is pointed out that if there is volume scattering, resulting from a stochastic variation in the index of refraction field, the method may be extended to determine the intensity corrections near a caustic due to this effect.© (1982) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Theory of quasi-optical antennas

Abstract: This chapter and the following one deal with the two principal types of quasi-optical antenna: reflectors and lenses. The principles of ray optics, as opposed to guided-wave or constrained-wave theory, are instrumental in their design. The term “optics”, however, is considered in its most general sense, and diffraction (e.g. physical optics, geometric optics and the geometric theory of diffraction) and aberrations are also included. In fact, the commonest microwave antenna, the collimating reflector, is a diffraction-limited device which is incapable of being analysed using ray optics alone. Other material in these chapters goes significantly beyond the normal realm of optical principles: e.g. spherical wave theory, tolerance theory, aperture blocking, frequency-selective surfaces, contoured beams and low-noise antennas. Yet these subjects are held together by the common thread of their direct applications to quasi-optical antennas.