# Resonance

Resonance — MC Grating documentation for Modal Collinear and Modal Conical and Chandezon Collinear and Chandezon Conical. The resonance search is aimed at…

Canonical: https://mcgrating.com/docs/common/resonance.html


Written by Nikolay M. LyndinLast revised 2016-10-16

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).

- The resonance search is aimed at searching for anomalies of the reflected and the transmitted waves when the incidence angle is changed in a fixed incidence plane. These anomalies could be caused, for example, by excitation of the waveguide modes the dielectric structure under modeling. For conical geometry the incidence plane is defined in the ***General*** page. It looks for the *pole* parameters (position - ***angle*** and ***width***) associated with the reflection (transmission) anomaly (resonance) of the selected polarization (***Polarization Output***). At the page opening the software automatically estimates the waveguide parameters by calculating the mode effective indexes of the multilayer structure under the assumption of a structure with real refractive indexes, the grating regions being considered as suitably averaged uniform layers. The exact resonance search can then be performed for a selected mode with the button ***Find*** and iteratively improved with the same button changed to ***Repeat***. The main resonance parameters are calculated on the basis of the phenomenological resonance response approximation by *poles* functions using five (single resonance) or seven (double resonance) equidistant angular positions located within an angular range covering four ***Half Resonance Width*** symmetrically with respect to the resonance ***Angle*** position. The exited mode effective index is calculated for excitation order defined by the user.
 If the ***Double Resonance*** check box is checked two consecutive poles will be calculated. This double resonance search is obligatory in two cases: first under normal incidence, secondly in the case of two neighboring resonances (poles).
- The full set of *poles* parameters can be found after the resonance searching by using an appropriate page of ***[Analysis](https://mcgrating.com/docs/common/analysis.html)*** dialog.
- The all fields and controls of this page are rather obvious.

**Note 1** The calculated mode effective index (***N Effective***) depends on the diffraction ***Excitation Order***. The program tries to determine this value, but nevertheless, the user is responsible for the final decision.

**Note 2** The user can try and find any type of resonance in addition to the mode resonances estimated above by editing values in ***Angle*** and ***Half Resonance Width*** field and using them as the starting values in a resonance search.

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