1,283 research outputs found
Analytic evaluation of diffuse fluence error in multi-layer scattering media with discontinuous refractive index
A simple analytic method of estimating the error involved in using an
approximate boundary condition for diffuse radiation in two adjoining
scattering media with differing refractive index is presented. The method is
based on asymptotic planar fluences and enables the relative error to be
readily evaluated without recourse to Monte Carlo simulation. Three examples of
its application are considered: (1) evaluating the error in calculating the
diffuse fluences at a boundary between two media with differing refractive
index and dissimilar scattering properties (2) the dependence of the relative
error in a multilayer medium with discontinuous refractive index on the ratio
of the reduced scattering coefficient to the absorption coefficient ms'/ma (3)
the parametric dependence of the error in the radiant flux Js at the surface of
a three-layer medium. The error is significant for strongly forward biased
scattering media with non-negligible absorption and is cumulative in
multi-layered media with refractive index increments between layers.Comment: 21 pages 7 Figures Text further revise
Calibration of a fission gas monitor
Calibration of argon gas neutron activation sampling devic
On Two Models of the Light Pulse Delay in a Saturable Absorber
A comparative analysis of two approaches to description of the light
modulation pulse delay in a saturable absorber is presented. According to the
simplest model, the delay of the optical pulse is a result of distortion of its
shape due to absorption self-modulation in the nonlinear medium. The second
model of the effect, proposed at the beginning of our century, connects the
pulse delay with the so-called "slow light" resulting from the group velocity
reduction under conditions of the coherent population oscillations. It is shown
that all the known experimental data on the light pulse delay in saturable
absorbers can be comprehensively described in the framework of the simplest
model of saturable absorber and do not require invoking the effect of coherent
population oscillations with spectral hole-burning and anomalous modifications
of the light group velocity. It is concluded that the effect of group velocity
reduction under conditions of coherent population oscillations has not received
so far any experimental confirmation, and the assertions about real observation
of the "slow light" based on this mechanism are groundless.Comment: Regretfully, the journal version of the paper (in Optics and
Spectroscopy) appeared to be strongly corrupted due to ignorant editing. In
particular, "coherent population oscillations" (CPO) was replaced by
"population coherent oscillations" (PCO), "bleaching" - by "clearing", and
"bleachable absorber " - by "clearable absorber". Here we present original
version of the pape
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