TFCalc 3.5 Changes

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Major New Features

There are a number of minor changes that are not documented here. The new features described here are in the Windows version only; except for bug fixes, the Macintosh version was not updated.


Analysis

  • Interactive analysis. This new feature enables the designer to change a parameter and see immediately how that change affects the performance. The following parameters can be changed: layer thickness (QWOT or physical), group factor, refractive index (N or K), incident angle, incident wavelength, electric field wavelength, monitoring wavelength, mixture percentage, and variable material factor. Each time the user changes one of these parameters, the following windows are automatically updated: Plot, Table, Electric Field, Color Chart, and Monitor Chart. Up to five of these "interactive analysis" dialogs can be open simultaneously. The sequence of plots generated by the interactive analysis can be saved as a GIF animation file.

  • Animations saved. When TFCalc produces a sequence of plots, that sequence can be saved as a GIF animation file -- a popular format for storing graphical information. There are two ways of creating animations: (1) using interactive analysis to save the contents of the Plot, EFI Plot, Color, or Monitor windows and (2) analyzing a coating for angles and wavelengths. In the latter case, there is a new command on the Plot window's Option menu: Save Animation to File. GIF files can be viewed in web browsers such as Internet Explorer and Netscape Navigator. QuickTime for Windows is another good application for viewing animated GIFs. (Due to resource limitations, Windows 95/98/ME users should limit their animations to about 50 frames.) Examples

  • Yield analysis. This feature can help determine the manufacturability of a coating design. The user must specify the coating's performance tolerance using inequality targets. Then the yield analysis uses parameters in the Sensitivity dialog to generate designs having small random errors. The yield is the percentage of these random designs that have performance within the tolerance. The yield analysis also plots a graph that indicates which wavelengths contribute most to the failure of designs to meet the tolerance.

    Unless a design must consist of all integer quarter-wave optical thickness layers, it is possible to use TFCalc's "optimize sensitivity" option in the Optimization parameters dialog to improve the yield of a design.

  • Ultra-fast performance computed. TFCalc can compute the ultra-fast quantities GD (group delay), GDD (group delay dispersion), and TOD (third-order dispersion). These are merely the first, second, and third-order derivatives of phase shift with respect to wave number. These quantities are available for reflection and transmission, and for P and S polarization and the difference P-S. These quantities are computed using numerical derivatives. Sample35

  • Backside phase. Now it is possible to calculate and optimize the phase shift from the backside of the coating. This feature is useful when performance from the front and back of the coating must be controlled.

  • Analysis parameters dialog revamped. There were two ways to analyze the performance of a coating: collimated light or a cone of light. In previous versions, TFCalc did not remember how the coating was analyzed. Now the parameters for collimated light and a cone of light have been collected in one dialog containing three panels. The first panel contains the wavelength and angle information from the old dialog. The second panel contains the cone angle information. The third panel contains parameters for phase shift and color. There is a checkbox that enables the user to select whether or not the cone-angle average should be computed.

  • Phase can be stored with an illuminant. Data about an illuminant can now include the phase shift as a function of wavelength. Phase information is important when designing coatings that control phase shift and its derivatives. If the illuminant's phase shift is not important, it should be set to zero.

  • Illuminant source. When results are saved as an illuminant, a comment is saved with the illuminant indicating source of the illuminant.

  • Dispersion of equivalent layers. When a layer is replaced by equivalent layers, it is sometimes useful to know how dispersive the layers are. The dispersion is now calculated for all HLH and LHL solutions found in the Compute Equivalent Stack dialog.

  • Four active materials. There are now four active materials instead of three.

  • Smallest wavelength is 0.1 Angstrom. This is important for designers of x-ray coatings.

  • Sensitivity: vary all indices independently. In the sensitivity dialog, the user can now choose to vary all layer indices independently. Previously, the material indices were varied; layers composed of the same material would always have the same index.

  • Sensitivity analysis works with cone angles. When "Compute Cone-Angle Average" is selected in the Analysis Parameters dialog (see above), then the sensitivity calculations are also performed using a cone of light. Note that this analysis will take significantly longer.

  • Sensitivity change. In the sensitivity dialog, the minimum allowable relative error is now 0.0001%.

  • Print stack formula. In the stack formula dialog, there is now a print button.

  • Equivalent index improvement. When computing the equivalent index of a sequence of layers, TFCalc now makes sure the layers are symmetric.


Optimization

  • Optimization using cone-angle targets. TFCalc has had the capability of computing the performance of a coating when illuminated by a cone of light for many years. Now the designer can also optimize the coating for a cone of light. Selecting "Targets - Cone Angle" from the Modify menu will open the window where cone-angle targets can be entered. Cone-angle targets work with all forms of optimization in TFCalc. Sample35

  • Optimization of ultra-fast quantities. A new command on the Options menu of the "Targets - Discrete" window is "Generate ultra-fast targets". This enables the designer to add targets for GD, GDD, and TOD. These targets work with all forms of optimization in TFCalc. Sample35

  • Inequality targets and tolerances can be read from a text file. Previously, all targets read from a file were equality targets. Now a target file can have three columns: wavelength, target value, and tolerance. If there is no tolerance column, a default tolerance is used. Here is an example of part of a target file: 
        500.0    >45.0
    500.0    <55.0
    550.0    100.0    0.1
    Note that a wavelength can appear more than once. The first two targets in this example would use the default tolerance; the third would use 0.1.

  • Equal-ripple targets. A new command on the Options menu of the "Targets - Discrete" window is "Generate equal-ripple targets". This feature is useful when designing equal-ripple bandpass filters.

  • Automatic design of bandpass filters. On the new "More Options" menu of the Layers-Front window, there are three commands for creating equal-ripple bandpass filters having up to 25 cavities. The user selects the number of cavities, bandwidth, ripple, and H and L materials. The three commands enable the user to (1) create a prototype bandpass filter, (2) convert the prototype to an intermediate design containing some variable material layers, and (3) convert the intermediate design into a real design by either (a) replacing the variable material layers with equivalent layers or (b) using 3-QWOT layers to eliminate the variable material layers. Sample35

  • Enter targets in dB. In the Discrete Targets, Continuous Targets, and Cone-Angle Targets windows, the optimization target can now be entered in dB. This is done by entering a negative number. For example, -0.5 will be converted to 89.1251%.

Materials

  • Mixtures of materials. On the Modify menu there is a new command "Mixture Materials" that displays a window that enables the user to make mixtures of two materials by giving the names of the two materials A and B, and the percentage of A. The mixture is just a linear mix of the dielectric constants of the two materials. The window also displays the refractive index of the mixture at the reference wavelength. If the user changes this index, the percentage of A will be adjusted to obtain the desired index. Mixture materials are important in at least two areas: (1) to determine the effect of impurities in coatings and (2) to create materials with special properties. Using interactive analysis, the user can adjust the mixture percentage and see immediately how the coating performance changes.

  • Dispersion formula constraints removed. Most dispersion formulas had parameters that were constrained to be non-negative. These constraints, which are used when the dispersion formula is fit to measured data, have been removed. However, the user can set these in the Constraints dialog.

  • Variable and mixture materials searched first. When TFCalc opens a design, now it searches for material names in the variable materials and the mixture materials lists before the regular materials list. When designs are received from other designers, this feature prevents a problem caused by designs that use a variable or mixture material whose name is the same as an existing material.

  • Variable materials factor. When designing a prototype bandpass filter using variable materials, it is sometimes desirable to adjust the width of the passband. This can be accomplished by multiplying all indices greater than 1 and dividing all indices less than 1 by a factor. TFCalc's new interactive analysis feature makes it easy to find the correct factor; just open an interactive analysis dialog, select "variable material factor", and adjust that factor while watching a plot of the filter. Animation example.


User Interface

  • User can change background color of windows to white. The gray background is too dark on some computers. White, though bright, improves the readability of data windows. Select the "Window Options" command on the Misc menu for this option.

  • Plots copied to the clipboard now have a white background. Previously, the gray background was copied to the clipboard. Now the background is always white.

  • Color printers detected. If plots are printed using a color printer, TFCalc will print solid lines instead of dashed lines.

  • Open files detected. When TFCalc tries to read a file that is being used by another program, it displays a warning message. Previously, TFCalc would fail to read the file and there was no message.

  • Radio buttons change automatically. When the user changes text associated with a radio button, the button is selected automatically.

  • Improved zooming. Now when you zoom a plot (by holding down the Control key while dragging the mouse), a green rectangle shows the area that will be zoomed.

  • Better error handling. Errors in TFCalc -- if there are any -- are reported with more information and stored in the file TFCalc.Log


Miscellaneous

  • Configuration parameters are stored with each design. This means that each design remembers the configuration settings (wavelength units, thickness priority, color observer, phase convention, etc.) that were in effect when the design was saved.
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