# Leo Enge: Periodic and Non-Periodic Filter Structures in Lasers

**Time: **
Thu 2021-01-07 10.00 - 10.30

**Lecturer: **
Leo Enge

**Location: **
Zoom, contact organiser

**Supervisor: **
Ander Szepessy & Jan-Olof Wesström (II-VI Incorporated)

### Abstract

Communication using fiber optics is an integral part of modern societies and one of the most important parts of this is the grating filter of a laser. In this report we introduce both the periodic and the non-periodic grating filter and discuss how there can be resonance in these structures. We then provide an exact method for calculating the spectrum of these grating filters and study three different methods to calculate this approximately. The first one is the Fourier approximation which is very simple. For the studied filters the fundamental form of the results for this method is correct, even though the details are not. The second method consists of calculating the spectrum exactly for some values and then use interpolation by splines. This method gives satisfactory results for the types of gratings analysed. Finally a method of perturbation is provided for the periodic grating filter as well as an outline for how this can be extended to the non-periodic grating filter. For the studied filters the results of this method are very promising. The method of perturbations may also give a deeper understanding of how a filter works and we therefore conclude that it would be of interest to study the method of perturbations further, while all the studied methods can be useful for computation of the spectrum depending on the required precision.

**Zoom note:** To get the link conact szepessy at kth.se.