Optical properties of surfaces. This project is intended to identify the needs of Swedish and Nordic industry for improvements in the field of optical measurement. We demonstrate an approach for modeling the optical properties of rough surfaces in COMSOL Multiphysics®. Read the full blog post. obtained over the years for the description of the optical properties of thin films .. It is the aim of this book to describe the optical properties of surfaces with a.
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That is, we generate a set of statistics by sampling the rough surface.
A rough surface with random variations reflects and transmits light in random directions. The computational model must sample a statistically significant subset of the roughness profile.
Our computational domain must now be very wide, many times longer than the wavelength. As we still want to optical properties of surfaces a plane wave incident at various angles on the structure, we use the Floquet periodic boundary conditions, which require that we have an identical mesh on the periodic boundaries.
Practically speaking, this means that we may need to slightly alter the geometry of our domain to ensure that the boundaries on optical properties of surfaces left and right side are identical.
Optical Properties of the Paint Surface
If we do use a sum of sine functions, as described herethen the profile will automatically be periodic. We still want to launch the wave with a Port boundary condition. However, it is no longer practical to use diffraction order ports to monitor the reflected and transmitted light, as this can result in hundreds or thousands of diffraction orders.
That is, this modeling approach optical properties of surfaces the total integrated scatter plus the specular reflection and transmission of the surface. The computational domain for a model optical properties of surfaces a rough surface.
Optical properties of surfaces
Light is launched from the interior port toward the material interface. Light reflected back toward this port passes though it and is absorbed in the PML, as is the transmitted light.
Two additional boundaries are introduced to monitor the total reflectance and transmittance. Thus, we introduce an alternative modeling strategy that does not use ports to compute reflection and transmission.
: Optical Properties of Surfaces : Dick Bedeaux, Jan Vlieger: Books
Instead, we use a perfectly matched layer PML above and below to absorb all reflected and transmitted light as well as probes to compute reflection and transmission. PMLs absorb any fields incident upon them, as described in optical properties of surfaces blog post on using PMLs for wave electromagnetics problems.
The PML absorbs both propagating and evanescent components of optical properties of surfaces field, but we only want it to absorb the propagating component. Thus, we again need to ensure that we place the PMLs far enough away from the material interfaces.
How to Model the Optical Properties of Rough Surfaces | COMSOL Blog
We use the same rule of thumb as before, placing the PML at least half a wavelength away from the material interfaces. As we approach grazing angles of incidence, even the PML domain does not, by default, absorb all of optical properties of surfaces light. At nearly grazing angles, the optical properties of surfaces wavelength in the absorbing direction is very long, and we need to modify the default wavelength in the PML settings shown below.
The PML settings modified to account for grazing angles of incidence. Since our domain is now bounded by PMLs above and below, the port that launches the wave must now be placed within the modeling domain.
To do this, we use the Slit Condition option to define an interior port that is backed by a domain.