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.

Sea Surface Kinematics From Near-Nadir Radar Measurements

Abstract: Doppler radars at all incidence angles measure mean velocities and spreads that have complex relations to oceanic motions, with opportunities to measure winds, waves, and currents. Here, we extend previous theoretical models of backscatter and Doppler using a Kirchhoff approximation and the physical optics model. We show that in Ka-band, around 12° incidence, range-resolved measurements of Doppler and backscatter provide unambiguous estimations of the wave spectrum and surface current. This property is illustrated with numerical examples and airborne data from the Air Surface Water Ocean Topography instrument. The same measurement conditions can be exploited for global ocean mapping from the low Earth orbit sensor satellite configuration.

Physical optics modeling and optimization of laser guide star propagation

Abstract: We use physical optics to simulate LGS propagation and imaging in a Shack-Hartmann wavefront sensor (WFS). We model different launch telescope (LT) sizes and realistic LT aberrations, the turbulent atmosphere, a sodium layer of finite thickness, the downlink propagation of the return light, an 8m-telescope, and finally the planned Very Large Telescope (VLT) Adaptive Optics Facility 40×40 GRAAL WFS. We study both long-exposure and instantaneous images on the WFS and compute spot size statistics. The results agree with observations obtained in the VLT telescope guider camera and enable us to optimize the LT diameter and devise design rules.

Scattering by periodic metal surfaces with sinusoidal height profiles--A theoretical approach

Abstract: A theory of scattering by periodic metal surfaces is presented that utilizes the physical optics approximation to determine the current distribution in the metal surface to first order, but modifies this approximate distribution by multiplication with a Fourier series whose fundamental period is that of the surface profile (Floquet's theorem). The coefficients of the Fourier series are determined from the condition that the field radiated by the current distribution into the lower (shielded) half-space must cancel the primary plane wave in this space range. The theory reduces the scatter problem to the familiar task of solving a linear system. For certain basic types of surface profiles, including the sinusoidal profile considered here, the coefficients of the linear system are obtained as closed form expressions in well-known functions (Bessel functions for sinusoidal profiles and exponential functions for piecewise linear profiles). The theory is thus amenable to efficient computer evaluation. Comparison of numerical results based on this theory with data obtained by recent numerical schemes shows that for depths of surface grooves less than a wavelength and for unrestricted groove widths, reliable and comparable, if not more accurate, data is obtained, in many cases at considerably cheaper computational cost.

Light scattering by ice crystals of cirrus clouds: From exact numerical methods to physical-optics approximation

Abstract: The problem of light scattering by ice crystals of cirrus clouds is considered in the case of a hexagonal ice plate with different distributions over crystal orientations. The physical-optics approximation based on (E, M)-diffraction theory is compared with two exact numerical methods: the finite difference time domain (FDTD) and the discontinuous Galerkin time domain (DGTD) in order to estimate its accuracy and limits of applicability. It is shown that the accuracy of the physical-optics approximation is estimated as 95% for the averaged backscattering Mueller matrix for particles with size parameter more than 120. Furthermore, the simple expression that allows one to estimate the minimal number of particle orientations required for appropriate spatial averaging has been derived.

Optical realization of the baker's transformation

Abstract: The quantization of a completely chaotic system-the baker's transformation-is investigated using the fact that the relationship between classical and quantum mechanics is directly analogous to the one between ray and wave optics. A class of optical systems is constructed for which the ray dynamics is governed by the baker map. Applying wave-optical methods to these physical systems then gives, in the standard way, their corresponding quantum dynamics. The result is that in certain cases the quantum propagator is identical to that found previously using an ad hoc mathematical quantization procedure. However, this is not always so-for other systems with the same classical (ray) limit there are important differences. In particular, the propagator need not be block-diagonal in its q-p' representation, as had previously been assumed, although it always tends to this basic form in the semiclassical limit.