Biomedical subjects

A A Maradudin

Publications and source records attributed to A A Maradudin.

4 recordsLinked to original sources

PubMed2005

Interference of a pair of symmetric Collett-Wolf beams.

We present a study of the interference of light produced by a pair of mutually correlated Gaussian Schell-model sources. The spatial distributions of the fields produced by these sources are symmetric with respect to a plane through their common center and differ by a phase factor exp(i phi). When phi = 0, the resulting radiation is a beam with an intensity distribution that displays a narrow bright line at its center. When the sources can be regarded as Collett-Wolf sources, the resulting bright line diverges much more slowly than the beam itself. When phi = pi the radiated beam has an intensity distribution with a narrow dark line at its center. The theoretical results are supported by experimental results obtained by use of a modified Michelson interferometer and suggest that the interference of a pair of correlated Collett-Wolf beams can be used to produce a pseudo-nondiffracting beam.

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PubMed2005

Coherence of light scattered from a randomly rough surface.

We study the coherence of p-polarized light scattered from a one-dimensional weakly rough random metal surface in contact with vacuum. The mutual coherence function of the single nonzero component of the scattered magnetic field is calculated in planes parallel to, and at increasing distances from, the mean scattering surface in the vacuum region. It is found to be the sum of a contribution that is independent of the distance from the mean surface and a contribution that is a function of this distance and decays to zero over a distance of the order of the wavelength of the incident light. It is also shown that the spatial coherence of the electromagnetic field in the far field in a plane at a fixed distance from the mean surface, as a function of the relative distance along it, mimics the surface height autocorrelation function at short relative distances and oscillates with two periods, T(1) = lambda and T(2) = lambda/sin theta(0), where theta(0) is the angle of incidence. The former is due to the excitation of lateral waves, while the latter is due to the coherent interference of the multiple scattering processes that lead to the enhanced backscattering effect. In the near field the spatial coherence of the electromagnetic field measured at a fixed distance from the mean surface displays oscillations that are due to the excitation of surface plasmon polaritons. The period of these oscillations equals the wavelength of the surface plasmon polaritons, while the exponential decay of their amplitude is determined by the energy mean free path of the surface plasmon polaritons.

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PubMed2004

Backscattering of light from a dielectric layer on a reflecting substrate.

Scattering of light from rough dielectric films is studied experimentally. It is shown that the interference pattern of the scattered field depends critically on the power spectrum of the roughness, especially on its long-scale component. When the height of roughness is small compared with the wavelength, the backscattering peak (if it exists) is due to the interference of the singly scattered fields; hence the properties of the backscattered peak are rather unusual. In particular, the width of the peak is determined by the thickness of the film and is independent of the parameters of disorder. The intensity of the peak increases with an increase of the rms height of the surface roughness and becomes independent of the rms when the roughness is of the order of the wavelength.

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PubMed2003

Two-dimensional random surfaces that act as circular diffusers.

We propose a method for designing a two-dimensional random Dirichlet surface that, when it is illuminated at normal incidence by a scalar plane wave, scatters the wave with a circularly symmetric distribution of intensity. The method is applied to the design of a surface that acts as a Lambertian diffuser. The method is tested by computer simulations, and a procedure for fabricating such surfaces on photoresist is described.

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