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.

Effect of perturbations on the widths of narrow morphology-dependent resonances in Mie scattering

Abstract: The extremely narrow morphology-dependent resonances of a microdroplet seen in Mie scattering are important for the nonlinear optical phenomena in these microdroplets, the large storage time being responsible for optical feedback. A formalism is developed within the scalar wave analog to calculate the change in the widths caused by a small perturbation, such as a distortion of the microdroplet shape from perfect sphericity. This formalism may be viewed as the generalization of the usual Rayleigh–Schrodinger perturbation scheme to the imaginary part of the energy. The results are checked against T-matrix calculations. In particular, it is proved that any perturbation can only increase the widths of these resonances, provided that terms of O(1/Q0) can be ignored in the first- and second-order corrections, where Q0 is the original quality factor of the resonance. The result can be interpreted in terms of a generalized golden rule and is relevant to similar problems involving quasi-normal modes in quantum mechanics. The full theory beyond the scalar wave approximation can be developed, and it is expected that all qualitative features will survive.

A comparison between GO/aperture-field and physical-optics methods of offset reflectors

Abstract: Both geometrical optics (GO)/aperture-field and physical-optics (PO) methods are used extensively in the diffraction analysis of offset parabolic and dual reflectors. An analytical/numerical comparative study is performed to demonstrate the limitations of the GO/aperture-field method for accurately predicting the sidelobe and null positions and levels. In particular, it is shown that for offset parabolic reflectors and for feeds located at the focal point, the predicted far-field patterns (amplitude) by the GO/aperture-field method will always be symmetric even in the offset plane. This, of course, is inaccurate fur the general case and it is shown that the physical-optics method can result in asymmetric patterns for cases in which the feed is located at the focal point. Representative numerical data are presented and a comparison is made with available measured data.

Microlens-array-based exit-pupil expander for full-color displays

Abstract: Two-dimensional arrays of microlenses can be used in wearable display applications as numerical aperture expanders or exit-pupil expanders (EPEs) to increase the size of the display exit pupil. A novel EPE approach that uses two microlens arrays (MLAs) is presented. The approach is based on cascading two identical microlens arrays spaced precisely at one focal-length distance with submicrometer registration tolerances relative to each other. The ideal MLA for this application requires a 100% fillfactor, sharp seams between microlenses, and a perfect spherical profile. We demonstrate a dual-MLA-based EPE that produces excellent exit-pupil uniformity and better than 90% diffraction efficiency for all three wavelengths in a color-display system. Two-MLA registration is performed with submicrometer precision by use of far-field alignment techniques. Fourier optics theory is used to derive the analytical formulas, and physical optics beam propagation is used for numerical computations. Three MLA fabrication technologies, including gray-scale lithography, photoresist reflow, and isotropic etching, are evaluated and compared for an EPE application.

Focusing of electromagnetic waves by paraboloid mirrors. I. Theory

Abstract: We derive a solution to the problem of a plane electromagnetic wave focused by a parabolic mirror. The solution is obtained from the Stratton-Chu integral by solving a boundary-value problem. Our solution can be considered self-consistent. We also derive the far-field, i.e., Debye, approximation of our formulas. The solution shows that when the paraboloid is infinite, its focusing properties exhibit a dispersive behavior; that is, the structure of the field distribution in the vicinity of the focus strongly depends on the wavelength of the illumination. We show that for an infinite paraboloid the confinement of the focused energy worsens, with the energy distribution spreading in the focal plane. 2000 Optical Society of America [S0740-3232(00)01309-0] OCIS codes: 260.0260, 260.2110, 050.1960, 260.5430.