3.1         Introduction

Let us firstly remind some general remarks concerning the QW-V2D. There are two important consequences of using the vector two-dimensional formulation of FDTD in cylindrical coordinates:

-        Firstly, QW-Editor generates only one layer of FDTD cells

-        Secondly, this layer corresponds to xrhalf-plane, above the axis of symmetry, which is pre-defined at r=0.

The above entail that in the QW-V2D regime, only half of a long-section of the structure in xr‑plane (in the QW-Editor and QW-Simulator referred as xy-plane) is considered (and this should be drawn by the user). It is very important that no elements, objects or ports may extend below the symmetry axis (into the r<0 (y<0) half-plane).

Since the physical structure is known to be axisymmetrical, the notions such as “level” or “height” (important when defining elements, objects, etc. in the UDO) along the j–direction are irrelevant. However, purely for compatibility with the 3D regime of QW-Editor, we define all elements at a fictitious level = 0 and of fictitious height = 1. The only exception is NTF (Near-to-Far transformation) box, automatically created form ntf_2dv.udo at level = 0.25 and of fictitious height = 0.5. These fixed fictitious values cannot (and should not) be modified by the user.

More information about specific aspects of FDTD analysis in QW-V2D can be found in Specific aspects of FDTD analysis in QW-V2D.

Let us point out what are the main practical conclusions of the above discussion concerning the specific features of QW-V2D:

1.     To draw the structure that will be analysed in QW-V2D, we need to simply draw a contour of a half of structure’s long-section. The structure should be drawn in a way that its symmetry axis coincides with project symmetry axis r=0 (in the QW-Editor and QW-Simulator referred as y=0).

2.     Each element of the structure is drawn with line segments by giving the coordinates of the following points.

3.     It is advised to draw the elements (as in point 2) counter clockwise, so that the medium assigned to the element will fill its inside.