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SCATMECH > Classes and Functions >
Surface Scattering Models
> Axisymmetric_Particle_BRDF_Model
class
Axisymmetric_Particle_BRDF_Model
The Axisymmetric_Particle_BRDF_Model implements the
theory of Bobbert and Vlieger for the scattering by a
sphere on a substrate, extended for an axisymmetric
particle on a substrate. Since the theory of Bobbert and
Vlieger requires that the particle remain inside a sphere
which does not include the substrate, there are conditions
under which the theory will not be valid for axisymmetric
particles. It is important that the user check the model
for convergence over the polar and azimuthal harmonic
orders. If the routines do not appear to converge, none of
the results should be considered valid.
Parameters:
| Parameter |
Data
Type |
Description |
Default |
| lambda |
double |
Wavelength of the light
in vacuum [µm].
(Inherited from BRDF_Model.) |
0.532 |
| type |
int |
Indicates
whether scattering is evaluated in reflection (0) or
transmission (1).
(Inherited from BRDF_Model.) |
0 |
| substrate |
dielectric_function |
The
optical constants of the substrate, expressed as a
complex number (n,k) or, optionally, as a function of
wavelength.
(Inherited from BRDF_Model.) |
(4.05,0.05) |
| density |
double |
The
surface number density of local scatterers
[µm].
(Inherited from Local_BRDF_Model.) |
1 |
| Shape |
Axisymmetric_Shape |
The shape
of the particle. |
Ellipsoid_Axisymmetric_Shape |
| n2 |
dielectric_function |
The
optical constants of the particle, expressed as a
complex number (n,k) or, optionally, as a function of
wavelength. |
(1.46,0) |
| n1 |
dielectric_function |
The
optical constants of the substrate coating, expressed
as a complex number (n,k) or, optionally, as a function
of wavelength. |
(1.59,0) |
| t |
double |
The
thickness of the substrate coating
[µm]. |
0 |
| delta |
double |
The
distance between the particle and the substrate
[µm]. This value is zero when the particle is
touching the substrate. It cannot be less than
zero. |
0 |
| lmax |
int |
Maximum
spherical harmonic polar order used in the calculation.
Setting this value to 0 sends a request to use the
value appropriate for the free-space particle, as
suggested by Bohren and Huffman. For negative values of
lmax, the lmax appropriate for the free-space particle
is increased by the absolute value of lmax. For an
accurate solution, convergence should be checked by
varying this parameter. |
0 |
| nmax |
int |
Maximum
spherical harmonic aximuthal order used in the
calculation. Setting this value to 0 sends a request to
use the value appropriate for the free-space particle,
as suggested by Bohren and Huffman. For negative values
of lmax, the lmax appropriate for the free-space
particle is increased by the absolute value of lmax.
For an accurate solution, convergence should be checked
by varying this parameter. |
0 |
| order |
int |
The
perturbative order for the solution. For the exact
solution, the order should be set to -1. When order is
set to 0, the model reproduces the Double_Interaction_BRDF_Model with a
MieScatterer. When order is
set to 1 or higher, matrix inversion is performed by
successive approximation. This parameter is included in
the model for pedagogical reasons and should be set to
-1 for the exact solution. |
-1 |
| Norm_Inc_Approx |
int |
A flag
indicating whether or not to use the Normal Incidence
Approximation in the calculation. This approximation
assumes that the reflection coefficients are constant
and given by their normal incidence values. This
approximation is valid for a perfectly reflecting
metallic substrate, or if the distance of the particle
from the surface is large. This approximation is
included for pedagogical reasons, and the flag should
be set to 0 for an accurate solution. See the reference
by Videen for
details. |
0 |
| improve |
int |
The
number of iterative improvement iterations. Routines to
set or get the number of iterative improvement steps
requested for improving the solution for each incident
angle. For lmax much larger than that
needed for the free-space Mie scattering solution, the
matrix inversion accumulates some significant errors
that propagate to the final scattering solution.
Setting this value to something other than 0 increases
the computation time needed for each different incident
angle. A value of 2 or 3 has been found to be
satisfactory under all conditions. |
0 |
See also:
SCATMECH Home, Conventions, Local_BRDF_Model, Axisymmetric_Shape
P.A. Bobbert and
J. Vlieger, "Light scattering by a sphere on a
substrate," Physica 137A, 209-242 (1986).
P.A. Bobbert,
J. Vlieger, and R. Greef, "Light reflection from
a substrate sparsley seeded with spheres - Comparison with
an ellipsometric experiment," Physica 137A, 243-257
(1986).
J.H. Kim,
S.H. Ehrman, G.W. Mulholland, and
T.A. Germer, "
Polarized light scattering from metallic particles on
silicon wafers," in Optical Metrology Roadmap for
the Semiconductor, Optical, and Data Storage
Industries, Angela Duparré and Bhanwar Singh,
Eds., Proc. SPIE 4449, in press (2001).
G. Videen, "Light
scattering from a sphere on or near a surface,"
J. Opt. Soc. Am. A 8, 483-489
(1991).
T. Wriedt and A. Doicu,
"Light scattering from a particle on or near a surface,"
Opt. Commun. 152, 376-384 (1998).
A. Doicu, Y.A. Eremin,
and T. Wriedt, "Convergence of the T-matrix method for
light scattering from a particle on or near a surface,"
Opt. Commun. 159, 266-277
(1999).
Include file:
#include "axipart.h"
Source code:
axipart1.cpp
axipart2.cpp
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Current SCATMECH version: 6.00 (February 2008)
This page first online: Version 5.00 (July 2005)
This page last modified: Version 6.00 (February 2008)
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