Modes

This page provides the user with the possibility to calculate the lamellar modes and overlapping/scattering matrix parameters or Fourier modes and scattering matrix parameters of a grating structure, and to analyze their values as well as to draw the eigenmode field distributions. Most of the controls of this page have an obvious meaning; only a few deserve an explanation:

• The Output Type control allows choosing the appropriate type of displayed coupling coefficients (Overlapping or Scattering for Lamellar and only Scattering for Fourier modes).
• The Incidence Layer edit window provides the possibility to select a layer of the structure where from an incident mode propagates towards one of the layer interfaces, and the Mode N edit windows provide the possibility to select the order of an incident mode whose effective index/permittivity is displayed under Mode Propagation control.
• The Output Layer edit window provides the possibility to choose which one of the adjacent layers or the layer itself contains the scattered mode and the Mode M edit window provides the possibility to select the order of this mode.
• The Output control informs which part (up or down) of the Overlapping/Coupling N to M mode Coefficient is displayed. If the Incidence Layer and the Output Layer is the same, the Up choice means the scattering from a bottom interface the Down choice corresponds to the scattering from a top interface.
• The Polarization control (in the conical mount version) provides the possibility to select a mode polarization type. In this case, the mode polarization is defined as TE if the mode has only the Y component of the electric field and as TM if the mode has only the Y component of the magnetic field.
• The Save Modes button provides the possibility to save in a text or data file an effective index and permittivity table of all modes for the selected Incidence Layer and optionally to save a N to M mode Overlapping/Scattering Coefficient table.

Note 1 If the layer index is 0 or N+1 (where N is the number of layers), this index corresponds to the cover or substrate media respectively.

Note 2 Modes of a simple (without grating) layer are enumerated as Raleigh modes including positive and negative indexes. Lamellar/Fourier modes of a grating layer are enumerated in decreasing effective refractive index for positive real part value.