# General Parameters

General Parameters — MC Grating documentation for Modal Crossed. General Number of Orders allow to define the number of orders along X and Y directions (the…

Canonical: https://mcgrating.com/docs/modal-crossed/general.html


Written by Nikolay M. LyndinLast revised 2017-03-04

This documentation was written for releases up to 2018 and is being revised. Some dialogs have changed since. If something does not match what you see, write to [mc@mcgrating.com](mailto:mc@mcgrating.com).

**General**

- ***Number of Orders*** allow to define the number of orders along* X* and *Y *directions (the total number of modes is the product of these values). The order values should be adequate to the number of appropriate Rayleigh diffraction orders in every layer. There is a possibility of automatic fixing of this problem (see page ***Options***).
 The Rayleigh diffracted order indexes are calculated in positive directions of *X* and *Y *axes.
- ***Wavelength***, measurement unit is *nm*.
- Grating ***Period*** field** **has two editor controls for periods along *X* and *Y *directions, measurement unit is *nm*. The selected Check box between these editor controls imposes constrain on period values preserving their ratio during editing.
- ***Polarization. ***The polarization state is defined by two electric field vectors ***Es*** and ***Ep*.** The wave vector ***k*** of the incident wave and these electric field vectors are mutually orthogonal. Vector ***Es*** is parallel the *X-Y* plane and vector ***Ep*** is parallel the incidence plane. Amplitudes of these vectors are defined by the ***State*** polarization angle and the phase difference between them is defined by the ***Phase*** angle.
 Angles measurement unit is *degrees*.
 Under exactly normal incidence it is impossible to define the incidence plane unambiguously. In this case depending on a coordinate system the software uses the following rules.
 - For the Plane base coordinate system a plane of AngleI changing is considered as the incident plane.
 - For the Grating base coordinate system a X-Z plane is considered as the incident plane.
- ***Incidence Angles,*** the angles definition is explained in the ***Structure Geometry*** picture. In the conical mount version the incident wave orientation is defined by two angles (definition depends on ***Coordinate System***). Theirs meaning are obvious from the pictures presented at the same page. Measurement unit is *degrees*.

From the in-application help of Modal Crossed, documented through 2018. If you publish results computed with MC Grating, see [how to cite it](https://mcgrating.com/references.html#cite).