Options

Common options:

• If the Save Settings box is checked then all Scanning, Fields and Options parameters will be saved in the structure file in addition to the parameters from the General and Layers pages. The part of the structure text file with settings is hidden for the user but accessible with any external text redactor.
• The check box Background calculation disables the output to the result editor window during the calculation process.
• If the Number of Modes Correction box is checked, then if necessary the software will automatically increase the value of Number of Modes to the value adequate the number of Cover and Substrate diffraction orders.
• If the Merge Adjacent Cells box is checked the software merges adjacent cells of identical permittivity. The first and last cells are not considered as adjacent.
• Check box Advanced Options is visible if the structure contains sections of Advanced Options. If the Advanced Options check box is not checked, the software ignores the Advanced Options sections in the structure.
• If the Favor Memory Consumption box is checked the software utilizes minimum possible memory to complete calculation. This option is incompatible with the field calculation and modes analysis.
• For a reasonable response of the other windows applications it is not recommended to increase the Calculation Priority greater than Idle.
• Calculation Direction option is useful for calculation of structures with a uniform layers stack. Calculation is faster if it starts from this stack section.
• For the Field calculation and to activate the page Fields the box Field Calculation should be checked at that the page Scanning becomes inactive. The Autoselect check box allows enabling/disabling of a conformation dialog appearance while the user enters the Fields or Scanning disabled pages. The fields are calculated in two steps: calculation of the structure for the fixed parameters followed by the field distribution calculation in accordance to the page Fields settings.
• If the Automatically Start Second Stage box is not checked, then the calculation will be stopped after the first step and the user should press Run to proceed with the second step. This option is useful to check the intermediate results in the editor window. Changes in page Fields do not activate the first step.

TMM options:

• If the Extended Regime box is checked the software detects the situation where some parts of the grating period became independent of each other for low order lamellar modes and then automatically splits by two all necessary Cells and applies a special procedure of modes orthogonalization temporarily. This situation occurs for a high refractive index contrast or for long period gratings and without special treatment it may lead to an accuracy loosing. The Cells splitting is permanent for Fields or Modes calculations.
• Interface Fields Matching Basis control defines a projection eigen functions set for an interfaces fields matching. The Adjacent Layers option means the applying of eigen functions of two adjacent layers simultaneously (combined approach) while the Cover Medium option means the applying of incident medium eigen functions set for all interfaces.
• If TMM method for TM polarization and metal structures gives a stupid result (for example the balance is larger than unity) the most probable reason is that the eigen modes search subroutine lost some modes. The parameters below allow to extend the modes search area in the complex permittivity plane and/or to change the search algorithm.
  Delta Argument parameter defines the fragmentation of eigen modes search contour. If the appropriate box is checked this value is fixed otherwise if the error will be detected the software automatically will try a new search with a smaller Delta Argument value and repeat it if necessary till the minimum value specified in the appropriate combo box.
  Segment Sub Divisions parameter defines the number of successive contour segments satisfying the Delta Argument condition for the termination of fragmentation procedure for these segments.
  Real Axis Extension parameter is applicable only for the TM polarization and if at any Layer Cell the permittivity real part is negative. Positive limit of search region equals to the maximum value of the layer real part permittivity plus parameter value.
  Imagine Axis Extension parameter defines the imagine axis limits of search region from the minimum layer imagine part permittivity minus parameter value to the maximum layer imagine part permittivity plus parameter value. For the TE polarization this parameter is fixed and equals to unity. For the TM polarization, if the appropriate box is checked, this parameter is fixed otherwise if the error will be detected the software automatically will try a new search with a higher Imagine Axis Extension value and repeat it if necessary till the maximum value specified in the appropriate combo box.
  If all refractive indexes of the layer are real the software uses an alternative faster algorithm and parameters: Delta Argument, Segment Sub Divisions, Real Axis Extension and Imagine Axis Extension are not applicable in that case.

FMM options:

• In the case of the TM polarization and a binary highly conductive metal grating the truncation of Fourier representation of Maxwell's equations generates spurious plasmon-like modes. These modes have anomalously high effective refractive indexes and are responsible for the so called numerical instabilities. They do not present in the real lamellar structure (TMM) modes spectrum. If the Neff Filter Level box is checked the software considers the modes with effective refractive index above the specified level as no propagating in the layers. These modes are still used at the interfaces field matching. This option may be used to suppress so called numerical instabilities. For more details see Ref.9 in the Introduction.
• If the Max Permittivity Order box is checked the software fixes the number of the direct and inverse permittivity Fourier set members to the specified value. This option may be used to simulate smooth permittivity distribution (see Note).
• If the Smoothing Walls box is checked the software introduces the sinusoidal transition of the direct and inverse permittivity between adjacent Cells. If one of the adjacent Cell has the length less than the specified transition length, for this situation the transition length will be taken equals to this Cell length. This option may be used to simulate smooth permittivity distribution (see Note).
• The other controls of the Fourier Modes Method Options panel allow evaluating of the layers permittivity distribution under calculation.

Note The Max Permittivity Order and Smoothing Walls special FMM options have not yet a rigorous mathematical basis and the user responsibility is to interpret results while using these options.