OptiLayer
Thin Film Software
OptiLayer software supports all sides of the
design-manufacturing-characterization process. The main module, OptiLayer, is the fastest optical design software. But an even
more important fact is that a carefully ellaborated interface and
a number of automatic modes enable the
solution of the most complicated design problems even by a user
without special experience in optical coatings design. Special design modes meet the
requirements of the most sophisticated designer and enable an
effective application of all his experience to the fastest
solution of various design problems. Diverse
analysis modes of OptiLayer
provide the user with all the necessary tools for
predicting manufacturing and application properties of any
design. Both design and analysis can be performed over wide
spectral ranges and wide ranges of angles of light incidence for
coatings with dispersive and absorbing layer materials.
A special module of the software, OptiChar, is inteneded for the optical characterization of
single thin films based on spectral photometric and ellipsometric
measurements. It incorporates a large variety of thin film models
that enable the user to investigate absorption in a thin film,
dispersive properties of its optical parameters, and the
dependence of optical parameters on the thickness of a thin film
(inhomogeneity). A special interface provides an opportunity for
a flexible and well-grounded choice of the specific thin film
model depending on the available experimantal data, its accuracy,
and a priori information about the optical properties of
the investigated thin film. Sophisticated mathematical algorithms
enable the user to reliably detect and investigate even the most
fine effects in thin films caused by a small absorption, small
bulk and surface inhomogeneities .
Another software module, OptiRE, is intended for post-production characterization and
reverse engineering of optical coatings. It provides the user
with various options for a more accurate determination of optical
parameters of layer materials, for the determination of
correction factors used for the quartz cristal monitoring of the
deposition process, and for the determination of systematic and
random errors in the thicknesses of layers of manufactured
optical coatings.
All software modules utilize the most
up-to-date software decissions which makes them extremely
convinient to use. OptiLayer
software operates under Windows 95, 98, 2000,
NT 4.0, XP.
This is the only thin film
software that uses threaded computations. This allows the user to
interact with the software without interrupting computations and
to obtain all other benefits of the modern Windows 32 bit
environment.
OptiLayer thin film
software
Alexander V. Tikhonravov
and Michael K. Trubetskov
copyright 1997-2008, OptiLayer Ltd.
Introduction
OptiLayer thin film software consists of
several modules: OptiLayer (design and evaluation), OptiChar (optical
characterization),and OptiRE (post-production characterization and reverse
engineering. All modules are compatible on the database level and can easily
exchange data. OptiLayer software operates under Windows 95 and Windows NT 4.0.
This is the only thin film software that uses threaded computations. This allows
the user to interact with the software without interrupting computations and to
obtain all other benefits of the modern Windows 32-bit environment.
OptiLayer software utilizes the most
up-to-date software decisions and has mathematical kernel designed on the
highest professional level. User interface of OptiLayer software confirms the
latest Windows 95 specifications and is extremely convenient to use.
General
OptiLayer software can operate under wide
spectral and angle of incidence ranges. The number of points of spectral or
angle of incidence grids is practically unlimited (up to 999*99). For user
convenience there are two main modes of the software: spectral mode and angular
mode. In both modes, targets (or measurement data in OptiChar and OptiRE) can be
specified over two-parametric (spectral parameter and angle of incidence)
domains. The spectral mode is more convenient when spectral dependencies of
coating characteristics are the main interest, while the angular mode is more
convenient when the user is mostly interested in angular dependencies of coating
characteristics. Spectral parameters can be specified in micrometers,
nanometers, angstroms, inverse centimeters, and electron volts. Angular
parameters can be specified either in degrees or in radians.
All programs of the OptiLayer software are
organized around discrete database directories which allow the user to store
data for specific problems in separately identified directories without mixing
them up. At the same time, convenient options allow the transfer of data files
between various directories. A special directory, CATALOG, contains data files
with standard light sources and a library of optical glasses.
Input
Options
All programs of the OptiLayer software
family have a set of original editing options, which enable convenient and fast
input of numerical and symbolic data. These options include linear and nonlinear
grid generators, column editor allowing the fast generating of data in columns,
copying, inserting and deleting options, pages editor allowing the fast
generating of huge arrays of data specified over two-parametric domains,
specific import options allowing easy input of numerical data from any external
ASCII file. The last options make OptiLayer compatible with all other commercial
thin film software packages and with the user's own software.
OptiLayer supports data acquisition from
the data files of widely used spectrophotometers and ellipsometers, in
particular, data files written in JCAMP-DX format.
Graphical
Options
Graphical options of OptiLayer software
will meet all demands of even the most captious user. The user can control the
display and appearance of all chart elements, label area, line, and data point
elements, control the scale and appearance of various types of axis, control the
positioning and appearance of various titles, footnotes, and legends, and do
much more.
Due to the implementation of threaded
computations the user has a unique opportunity to control and change chart
windows in the on-line regime without interrupting computations. Convenient
dialog boxes allow this to be done in a quite simple way.
Output
Options
Results obtained by the programs of the
OptiLayer software family are presented in a graphical form and in the form of
"Reports" containing numerical data and detailed text comments related
to these data. The user can print and save all chart windows and reports. Chart
windows can be saved as *.VTC files (special format of the powerful OptiLayer
graphical option 'Plot Engine'), *.WMF files (Windows metafiles format), *.BMP
files (bitmapped graphics format). Reports are saved as ASCII files.
Analysis
Options of the OptiLayer Program
The user can evaluate a large variety of
optical coating characteristics:
reflectance, transmittance, absorptance
for s-polarized light, p-polarized light and non-polarized light, phase shifts
on reflection and transmission for s- and p-polarizations, differential phase
shifts on reflection and transmission, ellipsometric angles psi and delta.
All characteristics can be evaluated over
arbitrary spectral and angle of incidence ranges. It is possible to calculate
color coordinates of a coating with an arbitrary light source in the reflected
or transmitted light of an arbitrary polarization. Luminous reflectance and
transmittance can also be calculated with arbitrary light source and state of
polarization. Evaluation modes of the program are accompanied with a set of
other convenient options. The user has an opportunity to average coating
characteristics over arbitrary spectral or angle of incidence ranges, to pick
out exact numerical values from the evaluation plots at arbitrary points, to
change the number of evaluation plots and their chart appearance in the most
convenient way.
Optilayer has a set of powerful options
for analyzing the influence of errors in parameters of optical coatings. The
error analysis can be performed in the case of errors in layer thickness, errors
in layer refractive indices.
The program can evaluate the sensitivity
of each coating layer to the errors in parameters of this layer and rank coating
layers according to their sensitivity to errors.
There is a number of other analysis
options with flexible setup interface, among them: admittance diagrams, plots of
the electrical field inside a coating, plots of coating refractive index
profiles.
Design
Options of the OptiLayer Program
Unprecedented design capabilities of
OptiLayer are provided by a flexible combination of various design approaches
with the most powerful modern design technique, the needle optimization
technique. The needle optimization technique was invented in 1982 by one of the
creators of the OptiLayer software and since that time the group of OptiLayer
developers has continually improved its mathematical algorithms. Due to this
fact, OptiLayer incorporates the unique know-how that is inaccessible to other
thin film programs.
Refinement modes of OptiLayer use the most
powerful first, second, and higher order optimization routines. OptiLayer is the
only one thin film software where all optimization routines are based on
sophisticated analytic algorithms for computations of gradients and Hesse
matrices of merit functions. These algorithms belong to the unique know-how of
OptiLayer developers. They provide the eminent convergence rate and accuracy of
the OptiLayer refinement modes.
The Needle Optimization AUTO mode of the
program enables the solution of the most complicated design problems even by a
user without special experience in the optical coating design. The choice of a
starting design is not critical for the needle optimization design procedure. It
is quite possible to start the procedure with an arbitrary starting design, for
example, a single layer. The most important parameter is the overall optical
thickness of a starting design. By successively increasing this thickness the
user can generate a set of designs having increasing numbers of layers and
decreasing merit function values. This will allow the user to choose the most
practical design and thus to deal with the intrinsic uncertainty of the
correlation between the number of design layers and the merit function value.
The Gradual Evolution mode of the program allows the user to generate a set of
design in an automatic regime.
The manual Needle Optimization mode meets
the requirements of the most sophisticated designer and enables an effective
application of all his design experience to the fastest solution of various
design problems. Combining various design modes of the program may facilitate
the solution of complicated design programs. The Random Optimization mode also
helps to do this. It automatically generates a set of designs that can be later
used as starting designs for the needle optimization procedure. The best designs
generated by the Random Optimization mode are stored in a special Collection
database. The program keeps a record of the designs obtained at different steps
of the design procedure. The corresponding database is called the History
database. This feature adds flexibility to the design procedure because the user
can easily return to the previous steps of the design procedure and try to apply
other design approaches.
The developers of OptiLayer gave much
consideration to the flexibility of the design procedure in order to provide the
user with the best possible opportunities to meet all practical requirements.
There are a number of auxiliary options, which help to meet various feasibility
demands. The Design Cleaner and Thin Layer Removal options allow the reduction
of the total number of design layers and the elimination of thin layers in the
design. The Target Modifier automatic option and Modify Target manual option
help to improve the fitting of the design targets.
Characterization
Options of OptiChar
OptiChar is intended for the optical
characterization of single thin films based on spectral photometric and
spectral/angular ellipsometric measurements. The determination of optical
parameters of single thin films from photometric and ellipsometric data is a
typical inverse problem and thus features all difficulties inherent to such
problems. The most serious ones are possible nonuniqueness and instability of
the inverse problem solution. According to the basic ideas of the theory of
inverse problem in order to overcome these difficulties one should apply special
mathematical algorithms and to take into account all possible a priory
information about the investigated thin film. The developers of OptiChar are
experts in the theory of inverse problems and thus have been able to implement
in the program the most advanced mathematical methods. At the same time the main
goal has been to provide a user-friendly and physics oriented interface, which
helps to obtain the most detailed and reliable information about the film being
investigated. The corresponding interface means are provided by the diverse and
flexible characterization options and by the number of auxiliary analyzing
options.
In OptiChar an optical characterization of
a thin film is based on a hierarchy of thin film models. The choice of a model
from this hierarchy depends on the available experimental data, their accuracy,
and the a priori information about the optical parameters of the investigated
film. Insight on the methodology of this choice is provided by the text
"Advanced Optical Coatings: Characterization" which is available to
the users of OptiChar. The Layer Characterization mode of the program provides a
choice of a model from the set of models of a homogeneous thin film. The set
includes models of absorbing and non- absorbing films, various types of the
refractive index and extinction coefficient dispersive dependencies. The user
can specify the limits for thin film parameters according to the a priory
information about optical properties of the investigated film.
Two modes of the program, Bulk
Inhomogeneity and Surface Inhomogeneity, allow the user to investigate the
dependence of optical parameters on the thickness of a thin film. The
investigation of the bulk inhomogeneity in the first, so-called Schr\"{o}der's
approximation, allows the determination of the degree of inhomogeneity of a thin
film. More exact approximations allow investigating the refractive index profile
of a thin film. The Surface Inhomogeneity mode allows determining the surface
inhomogeneity in the near substrate and the near ambient regions.
The hierarchy of thin film models can be
represented as a tree structure. To extract the maximum information from the
available experimental data the user should have an opportunity to browse along
the tree of layer models and to analyze the results of the layer
characterization using any particular model. This opportunity is provided by a
set of convenient auxiliary options. Results of the layer characterization using
each particular model are stored in a special database called the Collection
database. The information presented in this database allows the user to trace
the steps of the characterization procedure and to return to one of the previous
steps in order to use different models for the characterization procedure. A set
of graphical options and spreadsheet reports allow the user to analyze
characterization results and to examine the fitting between model and
measurement data. This helps to check the validity of each particular thin film
model.
The Modify Measurements option permits the
user to edit the measurement data being loaded in the RAM. This option increases
the flexibility of the characterization procedure. It allows the user to change
tolerances of measurement data, to exclude questionable measurement data, to
change the spectral range of the characterization procedure, etc. The Layer
Refinement mode allows the user to refine the results of the characterization
procedure when the input measurement data are slightly changed or when a good
approximation to the film parameters is already available.
The Substrate Characterization option is
used to determine optical parameters of substrates. As in the case of a thin
film on a known substrate it is possible to apply various substrate models in
the course of the characterization procedure.
Characterization
and Reverse Engineering Options of OptiRE
OptiRE is intended for the post-production
characterization and reverse engineering of optical coatings based on spectral
photometric and ellipsometric data. This program provides a feedback for the
design-manufacturing process. Its main purpose is to discover systematic and
random errors in parameters of produced coatings and thus to help raise the
quality of an optical coating manufacturing.
The Systematic Errors mode of the program
performs a search for systematic errors in layer thickness. Results obtained
with this mode are presented in the form of "correction factors" to
the theoretical thickness of layers of each particular material. This mode is
especially convenient for the calibration of layer thickness when quartz crystal
monitoring is used. It also helps to discover systematic errors in the case of
optical monitoring of layer thickness.
The Indices Correction option is purposed
for the post-production characterization of layer refractive indices. For
various reasons layer refractive indices in a multilayer stack may vary from the
corresponding indices being determined from single layer measurements and then
used for the computations of optical coating designs. The Indices Correction
option allows for the determination of practical indices more accurately and
thus provides a feedback to the design procedure.
The Random Errors mode performs a search
for random errors in layer thickness. This search is a multiparametric inverse
problem which solution may be unstable and non- unique. The mathematical
algorithms of OptiRE and accordingly its users-interface have a number of
additional options allowing the user to overcome the problems connected with the
instability and non-uniqueness.
The Quasi-Random Errors mode of the
program combines the features of the Systematic Errors and Random Errors modes.
It incorporates the sophisticated mathematical algorithm based on the most
advanced ideas of the theory of inverse problems (so-called ideas of the
regularization of the inverse problem solution). From a physical point of view
this algorithm takes into account possible correlations between errors in
thickness of layers of each particular material. A special "Errors"
spreadsheet allows the user to analyze the results of the reverse engineering
procedure and to separate random and systematic errors in layer thickness.
There are a number of auxiliary options
that help to extract maximum information from the available experimental data. A
set of graphical options and spreadsheet reports allows the user to analyze the
results of the reverse engineering and to examine the fitting between the
measurement data and the data corresponding to these results. The Modify
Measurements option permits the user to change tolerances of measurement data,
to exclude questionable measurement data, and to change the spectral and angular
ranges over which measurement data are specified. This may be useful for the
verification and the refinement of the results of the reverse engineering
procedure.
