Electrical Engineering FACULTY
Optoelectronics LABORATORY
LECTURER: Dr inż. K. Marszałek
Design of thin film optical filters using MCalc MULTILAYER
Calculation
(version 4.0.6)
Kraków 2012
Contents:
1. Introduction
2. Functionality decription
2.1. Design
2.2. Calculating Parameters
2.3. Analyse
2.4. Monitoring
2.5. Refining Target
2.6. Color CIE
2.7. Load/save options for Project and filter analysis.
2.8. Material Data.
2.9. Adding nw materials
3. Introduction to CIE theory and LAB
4. Filter examples
4.1. TiO2 + SiO2 filter – reflection under 1% in 400÷700 nm region.
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1. First Introduction.
MCalc program is used to design thin-film filters for electromagnetic radiation in any region
of the spectrum. It creates graphs of transmission and reflection, depending on the
wavelength. With this program you can simulate arbitrarily changing the filterparameters
(thickness, material, etc.). One of the parameters is the refractive index, which is not constant
for a given material for electromagnetic waves of different lengths. The program included
tables of the refractive index of various materials available for constructing a filter- in more
detail in Section 2.8.
2. Second description and program functions
Most of the options program is distributed in six tabs as described in subsections
2.1 to 2.6. In subsections 2.7 to 2.9 are described in other program options, such as
options associated with the type of material and options for transferring data from
outside (eg for treatment of another program), import data into, or counted the value of
preserving and / or setting the filter.
2.1. Design.
Filter plate is called a uniform material that is ground (Substarate) for thin layers produced
(steamed) on its front (Frontdesign) and posterior (Backdesign) surface. The entire filter
can be placed in a certain neighborhood, or contact (link) with some element of the front
side of the filter(Medium 1), as well as and from the rear (Medium 2). Such a system
diagram of Figure 1 shows the filter
Figure 1 Diagram of the filter shown in the middle of the tab with the design (Design).
If not defined the layout of the filter (for Backdesign
and Frontdesign), then the diagram does not appear appropriate color block.
Tab design has three key elements:
Symbolic Input - the field to edit the filter layer by typing certain characters.
Semantics: a layer represents a point (as defined in the Material Database
MaterialID block - see below), it is not necessary to share a space each letter,
number of layers (eg AB) can be duplicated
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of optical thickness (eg 1.89A); its absence indicates the optical thickness
equal to 1. In the title block also contain an indication that the system is
currently being edited, which is from the pad of the electromagnetic wave.
After run the program, this field contains the typed "factory" formula for
systems for front and rear of the filter. With this feature are associated the
buttons (located on the subject):
Backside (Frontside) - undo button switches between the parties of the
substrate (Substrate); an inscription in the button indicates the side to edit
and switches the filter after it is pressed
Translate - a button to define a given system (Backside or Frontside) entered
in the field of Symbolic Input. Defined system appears in the table below
(Table described below). If the field is blank Symbolic Input table is
cleared, and vice versa (Translate Back button).
Translate Back - the acting contrary to the above. Symbolic input field is
filled like the system defined in the table.
Material Database - is the table containing the definitions of various
materials that can be used to construct various elements of the filter.
Material ID column contains the IDs of materials: Substrate indicates
surface; Medium 1, Medium 2 - Ambient filter and letters from A to Z as
representations of the materials used to construct the filter layer systems; in
the column Refr Ind / Material (Refractive Index / Material) is contained the
corresponding values of the refractive index n (Refractive Index) or selected
from a list of materials as defined in the Material Data (what is it and how to
use to built-in materials description in the description paragraph. 2.8 and 2.9
) - The material selection list will appear by double-clicking on the selected
field. Typing in this box indicates the environment. Tooling column changes
the optical thickness (Optical thickness) of all layers of the type used in the
construction of the filter. It should be in mind that when changing the optical
thickness of one type of layer all the other layers are set according to this
column and is therefore not advisable to use this column.
The third key element of the tab design (Design) is a table containing a defined
layer of the system (from the table the data are retrieved for calculations). This
table
contains the column:
Layer No. - Ordinal number of the layer system.
Layer ID. - Ordinal letter of the material from the Material Database block in
the Material ID column.
Material. - Specifies the type of material (name) defined in the Material
Database block Column Refr Ind / Material (if the chosen material is
available in the program, if not - indicates the index of refraction).
Refractive Index n. - optical refractive index n of the material.
Optical Thickness. - Optical thickness. This column can be edited.
Geometrical Thickness. - The geometric thickness measured in nanometers.
This column can be edited.
Refine (Yes / No). - Determines whether the material will be purified. A single
click changes between the two options for given layer.
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Testglass, XTC Toolings, these are the columns of the table used to work with the
device for the production of thin surface. Using these options is possible, when the device
have a suitable measuring elements.
Remarks, these are comments on a given layer.
Editing data in a given row is done by placing the cursor in the edit box with the
mouse (double click) and keyboard (press Enter), the next step is to enter from the
keyboard and the Enter key to confirm.
In addition to the manage data in the table buttons are (see Figure 2):
Copy Layer, the key used to copy single or multiple selected layers of the system.
Paste Layer, the key is used to paste previously copied layer
in the selected field by placing the check box under pasted layers.
Insert Layer inserts a single layer to a table in the selected location.
Delete Layer, removes the selected layer from the table.
Append Layer, insert a single layer in the table at the end.
Reverse Sequence, inverts the order of selected layers.
Keys Insert Layer and Append Layer always insert the item with the beginning
letter, "H", of course, then it is possible to change to something else.
The keys become active only after the selection of layer(s).
Selecting the layer(s) is done by selecting the appropriate row in column
Layer No.; selected layer is highlighted in blue on the entire length of the table.
Picture 2. Toolbar of MCalc program. Six last icons in the red frame depicts (from left side): Copy
Layer, Paste Layer, Insert Layer, Delete Layer, Append Layer and Reverse Sequence.
The buttons associated with the table, are Refine and No Refine - these buttons
determine whether the material of which a given system consists is cleaned. The term
"purity" of the individual layers can be changed in the table with a single click on the
appropriate line in column Refine. The tab Refining the Targets contains options for
changing settings for purification.
On the design tab there is still one more function started by Batch time button. This is
a function to specify how long will take the machine to produce a filter with preset values
(eg, during warm-up time of the machine, etc.).
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2.2. Parametry obliczeniowe (Calculation Parameters)
The analyse of the filter plot for the Transmission and the Filter and Reflection Wave
from the Surface of the filter consist of a percentage of the Wavelength. In this tab are the
option to set the configure parameter of the analyse-chart.
The tab consist of five seperate blocks:
Select Calculation Mode – in those three domains you can set the X-Axis , the YAxis and the Calculation Mode parameter. In the X-axis you can only choose the range in
nanometer, and for the Y-axis you can choose the following parameters:
Transmittance [%] – Transmission wave through filter (Transmission factor)
Reflection [%] – Reflection of the wave filter
Transmittance p-Pol – Transmittance of the p-type wave
Transmittance s-Pol – Transmittance of the s-type wave
Reflection p-Pol – Polarisation of the p-type wave
Reflection s-Pol – Polarisation of the s-type wave
Transmittance [dB] –Transmission factor of the wave through the filter in decibel
In the block Calculation Mode you can choose between Calculation without
Dispersion (Dispersion No), with Dispersion (Dispersion) and with Dispersion and
Absorption (Dispersion + Absorption).
General – Option in which you can choose Angle of incidence; Reference
Wavelength; Include Backside Reflection and you can choose if you like to see the visible
colors in the chart analyse (CIE Colors).
X-Axis parameters – You can set the minimum and the maximum Wavelength and
the Wavelength step in nanometer if calculate with reflection.
The hole block is disable when your current Design is in process Backside (Substrate)
Y-Axis parameters – You can set the minimum and maximum label of the Y-axis
Caption – Information about the chosen parameters in the section Select Calculation
Normally the standard parameters (default parameters) are good enough for a first
analyse. Sometimes at the beginning it is easier to find the reflection if you set the YMax
to 100% (standard is 5%), so you are able to see the hole Reflection process.
Default settings of Calculation Parameters card are very often enough for Basic
analysis. However, sometimes, for Reflection it’s better to see the changes if we set Ymax for 100% (5% as default) – We may see whole reflection, then.
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2.3. Analyse
When the filter is ready we may plot transmission/reflection to wavelength plot.
One of the most important functions of plotting is ability to place several plots on one
Picture using Overlay function (places next plot on the same picture - fig. 3) No Overlay
function is also available – plots new chart in the painting field.
Rysunek 3. Toolbar of MCalc program. Two buttons marked with red rectangleare (from left): No Overlay
and Overlay. After expanding Analyse (list (also in red rectangle) both functions are also available.
Overlay plots graphs changing line color, so we hale 6 dfferent plot colours: blue,
green, light blue, red, violet and yellow.Sefenth plot in the same diagram will be painted
using first color and so on. Using this function we must look out when we for example:
plot transmission (by default: Y-Max = 100%) and then (using Overlay) reflection (again
by default: Y-Max = 5%), ytthen program won’t fit scale of Y axis–Y scale will be taken
form 1st plot treated as 0 to 5 % Scale.The same wraining with X axis scaling.
Sumimng up, we need to look pout when plotting several graphs in one coordinate
system to identically scale X i Y axes of evere plot. Hence we will exclude element
causing bad conclusions.
Rysunek 4. Menu bar of Analyse.tab. Some transmission charts in background.
When we right-click mouse on the plot (figure 4), we have a few options to
choose:
Cursor - this option switches between a cursor and function analyze cursor mode
(cursor changes into horizontal arrows with vertical, green line). In the bottom
part of the screen (Status bar ) it shows value of function for selected
wavelength from recently plotted graph (figure 5). In this mode, after left-
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clicking mouse small cross appears on plot. This cross shows the reflection
function point corresponding to proper wavelength (Reflection z Include
Backside Reflection – more in 2.2).
Figure 5. Fragment of plot with vertical (green) line showing value of wavelength
and corresponding value on Y-axis and Status bar (grey strip on the bottom of
the screen), showing (from left): number of plots in one coordinate system, No
of Layers - number of filter layers, Wavelength – wavelength value shown by
vertical line, R/T - value R or T (on Y-axis) corresponding to proper
wavelength. Violet plot is the most recently added one.
Target Input - (?)
Zoom In - zooming in the selected part of plot
Zoom Out - returns to main view - showing whole plot on one screen
Copy - copies the whole plot (as picture file) to clipboard
Copy Data:
Each Value - copies values of function in a worksheet form. You should check
program options Misc > Options > Clipboard, if you have any problems with data
pasted to worksheet (treating data as text, instead of numbers) changing the
floating-point separator (dot or coma) should help .
Every 2nd Value - the same as above, the only difference is it copies every second
value.
Thick Line - switches between drawing a plot with thick/thin line
Edit Graph - choosing this function causes showing the Format Diagram window
with available options for formatting the plot. Figure 6 shows that window. The
only card which has available options is Title, (Axis card does not have any
available options, Grid card has some, but none of them works properly). To sum
up, in Title card, we can add the plot title, by typing the name into textbox;
tihen we specify which one, it’s type (reflecitron/translation) and with what axes
borders will be the last plot plotted (we can see it on pic 6 – many plots In the
background, and only last one in the window) to set we use Accept key and
then OK for confirmation.
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Rysunek 6. Format Diagram window – for plot options setup.
Edit Legend – wexecutinmg this function allows us to edit the description of the
plot. For this task – window appears (fig. 7), and there we place the table with
colums called Legend Text (function description) and Color (its color). Show
Legend option toggles showing the legend next to the plot.
Fig. 7. Edit Legend window of Analyse used for making plot description.
2.4. Monitoring
This tab provides a tool to analyze the reflection and not a function of
translation wavelength, but as a function of optical thickness of the filter, and a
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few other features. Data is divided into two blocks: the settings and watch
(monitoring). Function block settings are described below, the block contains
three distinct viewing the inner tabs (located in the lower left corner of the
block): Monitoring, Runsheet and Analyse. Monitoring tab is a graph
generated by the block Monitoring tab settings. Runsheet tab is only part of
information - it gives a description of the layers in the filter table of the test by
pressing the Create Runtable (described below). Analyse tab is a
generalized version of the main tabs to determine the transmission and
reflection waveforms (Analyse) program. Allows you to change the mode
(transmission / reflection), amend the limits of X and Y axes, change step
calculations (density calculations) and the only option to draw the graph
represented by the key No Overlay (new chart on the new coordinate system).
It is still in the card is added Analyse the plot option page, or function (if
enabled) adds (Overlay function) another plot to the main tab Analyse.
Figure8 window with a block monitoring card settings. It is located on the
left and right there is a window with a block monitoring.
Figure8 shows a block to the settings tab browning
Starting form the top:
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Calculation mode - the choice between reflection (Reflection), and transmission
(Transmittance).
Backside Refl (Reflection) - should it be considered a reflection of the back side of the
filter. It works the same way as Include Backside Reflection from the parameters of
alculation tab (Calculation Parameters).
Minimum R / T - lower limit of Y axis
Maximum R / T - upper limit of Y axis
Optical Thck Min (Minimum Thickness) - Lower limit of the X-axis
Optical Thck Max (Maximum Thickness) - upper limit of the X-axis
Optical Thck (Thickness) Step – calculations density – per how many optical thicknesses
reflection or transmission should be calculated
Refr Ind TG (Target Refraction Index) - the target refractive index
Mon Wavelength - wavelength reference
Testglass No - this is an option associated with the device producing thin layer
Auto Scale X - automatically adjusts the upper and lower limit of the X-axis
Square Simulate Signal - a signal simulating a square
Calculate - generating the chart
Create Runtable - button creates a table of data browsed filter Runsheet tab.
Settings - by pressing this key appear: "Mark layers, When trigger point is different from
next turning point (TP) to R /T X% ", which means: "Highlight the layer, at which point
downward differs from next to X% ", where X is a digit (0 to .. 100). The result of the use
of this function is changing the color of those parts of the course graph, in which the
difference between the near-peak and valley graph is less than or equal to the size entered
in%. This function is optional.
2.5. Refinijg Targets
This tab contains information abort clearness of material (Refine).
2.6. Color CIE
In tihs tab we may find XY cordinates graph with contour of colour plain marked
(module CIE 1931 Standard Observer 2°; D65 illuminat – look In charter 3). At the
bottom of the settings block using option View all colors on screen we may fill up the
contour. Above, there are fields containing X, Y i Z CIE coordinates pointed by a mous on
the colour pattern and the pointed colour In a small square.
This tab is used to define the net colour of te prepared filter. (what will be the colour
of light reflected by a filter as seen from observer perspective). Calculate button calculates
this colour; additionally the coordinates of calculated colour in the CIE scale and L*, a*, b*
are given; the bigger square next to them shows this colour; the position of this colour is
marked by X mark on the colour plain.
2.7. Load/save options for Project and filter analysis.
S The design of the filter is finished. Analyses has been made. All we nneed to do is
to save our work.
Saving project design can be made using File > Save (or File > Save Design As, if we
want to save in another file).We load design using Load Desingn option. Newly opened
window has useful option Auto Preview which show fragment of transmission chart.
Program has also tool to import spectral data files generated by spectrometers (Import
Spectral Data): *.sp, *.dx – Perkin Elmer; *.csv – Varian; *.spk – Eta and text files (Ascii
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Files). This function has options Overlay (add) and No Overlay (new) generating charts
(choice in a window) transmission, reflection, and absorption.
Program can also print results received. Just the Analyse chart (File > Print > Graph)
or more detailed description (File > Print > Report), where also table with Filter Layers
Substrate and Medium data is included.
In subchapter 2.3 you may find information abort how to copy chart values to
clipboard and then to another program, eg. for further treatment.
In subchapter 2.9 we may find information abort how material data (refractibe index
value in wavelength function ) can be copied to clipboard.
the labor contractor (Material Data).
List of materials (depending on the refractive index of
wavelength for a
given material):
Ag, Al, AL2O3, Al2O3Syrus, B270, BK7, DRALO,
Glas808462, h1, H4, Herasil,
HfO2, LASFN9, LIMA, LIMA8, MALBUNIT, MGF2,
OS_50, Sapphire, SiO2,
SiO2B, SIO2TMDS, Suprasil, TA2O5, TA2O5APS,
TA2O5DWD, Ta2O5gr, TI3O5,
TiO2, TiO2_APS, TIO2APS, TIO2KALT, TMDS,
TOPCOAT, ZnS, ZRO2.
List of metarials colected by labor contractor:
Source:
http://astron.berkeley.edu/~jrg/MATERIALS/node2.htm
Materials: Glass BK7
Source: http://www.crystran.co.uk/index.htm
Materials:
higher data standard:
Calcium Fluoride CaF2
Lithium Fluoride LiF
Magnesium Fluoride MgF2
Silver Bromide AgBr
Silver Chloride AgCl
Germanium Ge
Silicon-FZ (?) Si
Thallium Bromo-Iodide KRS-5 Optical Crystral (TlBr-TlI)
Caesium Iodide CsI
Caesium Bromide CsBr
Sodium Fluoride NaF
Zinc Selenide ZnSe
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Zinc Sulphide (Forward Looking Infra-Red - FLIR - grade)
ZnS
Zinc Sulphide (Multispectral grade) ZnS
Rubidium Bromide RbBr
lower data standard:
Sapphire Al2O3
Crystal Quartz SiO2
Thallium Bromo-Chloride KRS-6 Optical Crystal (TlBrTlCl)
Sodium Chloride NaCl
Potassium Bromide KBr
Potassium Chloride KCl
Potassium Iodide KI
Gallium lanthanum sulphide (GLS) glass
Rubidium Chloride RbCl
Rubidium Iodide RbI
2.8. Dodawanie nowych materiałów.
FIlters are beign made form materiale butli In the program or with dconstant
material’s refractive indexes enterred manually (Design > Material Database > Refr
Indx/Material).
material’s refractive index is changing depending on the wevelength so it’s
comfortable to use gathered tabular values which can be fund in many sources.
Manual addition of tabular materials is possible. Single material’s data are available
in *.mat file In main program catalog (C:\Program Files\Common Files\MCalc – katalog
domyślny), where * - name of material
Structure of material’s file: file name – material name; digit In first row of file show
Numer of data; starting form second row data domposed in 3 columns starts:: wavelength
in nm; corresponding refractive index n and Absorption coefficient k, so (?) here, the terror
is possible, because, abs. coeff. Is not k, but alfa, and between k and alfa there is a
dependency. Data row is beginned and ended with a quotation mark and values are
separated with semicolon. Dot is a separator in floating point number. FIle can be made
with any test editor (text mode), or with butli In editor (description below).
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Fig. 9. Toolbar of MCalc. Red-marked button is Edit Material. After expending Edit (also marked with
red line) can be found under Material Data….
On fig. 9 we can see a button allowin to show Edit Material window.
Newy opened windowi s divided for 2 main modules (tabs): Dispersion Table and
Dispersion Formula. In thew title of the window we may find the information about what
material are we editing (which file). Below me may choose the material to edit form
available matierials (mat files) – Name of Material.
In Dispersion Table tab we may find material data edition table with columns:
Wavelength – respective to the Refraction Index and Absorption coefficient k, so (?). If we
want to add New/edit material we fill up missing rows in the table.
To manage material files we use buttons available on the bottom of the window. We
may find such buttons: Exit, New Material – clears data from table and prepares window
for New edition; deleting material file from hard drive - Delete Material; savubg changes
in material file - Save Material and copying Dispersion Table contents to Clipboard Copy Clipboard. Last one copies up to 50 positions with dot aas floating point separator.
Dispersion Formula tab (fig. 10) gives opportunity to generale data to Dispersion
Table.
Rysunek 10. Dispersion Formula. tab
3. Introduction CIE system theory and CIELab.
4. Filter examples
4.1. Filter preparation step by step
4.2. TiO2 + SiO2 filter – reflecti0on below 1% in 400÷700 nm range.
Not included:
Edit>Copy>Plot >Design >Monitoring
Analyse>Filter Performance
Misc>Options (wspomniane)
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Errors In program/remarkl:
Material Data > Copy to Clipboard copies maximum of 50 elements and only with “.”
Fluorides (there is a couple)
Oxides
Nitrides
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