Biomedical subjects

Aristide Dogariu

Publications and source records attributed to Aristide Dogariu.

6 recordsLinked to original sources

PubMed2003

Optical path-length spectroscopy of incipient caries lesions in relation to quantitative light-induced fluorescence and lesion characteristics.

A basic understanding of the light-scattering processes that take place inside the dental tissue (either sound or carious) is obtained both with measurements of the photon path-length distribution of light inside such media and with Monte Carlo simulations. Furthermore, the following is investigated: the correlations between different momenta of the photon path-length distribution of light inside caries lesions, the fluorescence loss determined with quantitative light-induced fluorescence, and/or the demineralization and depth of caries lesions determined with transversal microradiography. It is concluded that (i) the light paths inside both carious and sound enamel are considerably influenced by the refractive-index contrast at the tooth surface; (ii) contrary to a previous hypothesis, the fluorescence loss is larger in lesions in which the average photon path length is longer; (iii) very good correlations are obtained between the optical characteristics and the physical parameters of lesions when the optical measurements are performed such that there is high refractive contrast at the tooth surface.

Dental Caries↗

PubMed2003

Directionality of Gaussian Schell-model beams propagating in atmospheric turbulence.

It is known that some partially coherent Gaussian Shell-model beams may generate, in free space, the same angular distribution of radiant intensity as a fully coherent laser beam. We show that this result also holds even if the beams propagate in atmospheric turbulence, irrespective of the particular model of turbulence used. The result is illustrated by an example.

Journal Article↗

PubMed2003

Propagation of partially coherent beams: turbulence-induced degradation.

We show that, when a partially coherent beam propagates through an inhomogeneous medium such as atmospheric turbulence, the phase randomization that is induced is less effective in degrading the spatial coherence properties. By evaluating the final beam widths we report what is to our knowledge the first experimental demonstration that, on propagation through thermlly induced turbulence, a partially coherent beam is less affected than a spatially coherent beam.

Journal Article↗

PubMed2003

Mode analysis of spreading of partially coherent beams propagating through atmospheric turbulence.

The spreading of partially coherent beams propagating through atmospheric turbulence is studied by use of the coherent-mode representation of the beams. Specifically, we consider partially coherent Gaussian Schell-model beams entering the atmosphere, and we examine the spreading of each coherent mode, represented by a Hermite-Gaussian function, on propagation. We find that in atmospheric turbulence the relative spreading of higher-order modes is smaller than that of lower-order modes, whereas the relative spreading of all order modes is the same as in free space. This modal behavior successfully explains why under certain circumstances partially coherent beams are less affected by atmospheric turbulence than are fully spatially coherent laser beams.

Journal Article↗

PubMed2002

Measuring the phase of spatially coherent polychromatic fields.

Realistic optical fields are never completely monochromatic and the interpretation of the concept of phase is not straightforward. It has been pointed out by Wolf that, if a strict condition of spatial coherence is imposed, the statistically averaged behavior of a polychromatic field can be described by an associated monochromatic wave. We show that, for spatially coherent polychromatic optical fields, the measurement of the phase of the second-order correlations determines the phase of this associated, spatially coherent field. We verify this prediction using a novel interferometric technique for measuring the cross-spectral density of a steady-state optical field.

Journal Article↗

PubMed2002

Off-diagonal Mueller matrix elements in backscattering from highly diffusive media.

Measurements of a reduced Mueller matrix in backscattering from highly diffusive, dielectric samples are reported as a function of the angle of incidence. It was found that the off-diagonal terms depend greatly on the angle of incidence, increasing to a maximum near grazing incidence. We show that, despite a significant scattering originating in the bulk of such diffusive media, the nontrivial behavior of the off-diagonal Muller matrix is primarily due to surface scattering phenomena. The experimental data can be simply explained by assuming a random orientation of small particles and considering only double scattering in the plane of the surface.

Journal Article↗