The following is only available in FDTD and MODE:
This section describes how to create various waveguide bends using the waveguide object. The path of the waveguide is a Bezier curve, which is defined by a set of points, called 'poles.' Further detail on Bezier curve can be found on the ' Structures - Waveguide' page.
The example file, usr_waveguide_bends.fsp, contains an s-bend and a Y-branch, which can be used to build more complex structures such as cascaded y-branches and directional couplers.
Creating an S-bend
The s-bend waveguide can be created by specifying the poles in the 'edit waveguide' window. The red dots in the image below corresponds to the poles in the table on the right. The example s-bend can be located in the usr_waveguide_s_bend.fsp.
If only two poles are specified, a straight waveguide is formed.
Creating a Y-branch
Using the straight and the s-bend waveguides as building blocks, a Y-branch structure group as shown below can be created. The group contains two s-bend as well as three rectangles. The dimensions of the waveguides (x1, x2, y2) can be parametrized and a script in the structure group can be used to build the structure automatically. This is a good example of a parent structure script modifying child structure scripts.
The following script is used in the 'script' section of the structure group:
Note: Reference points
The pole points are defined at the center of the waveguide cross section. The x1, x2, and y2 in the Y-splitter example are all measured with respect to the corresponding pole points.