Launch Fields define where light will enter a photonic device in Rsoft CAD. An example that uses multiple launch fields is the beam combiner.
On the sidebar, select “Edit Launch Fields”. To add a new lauch, select New and chose the pathway. A waveguide will be selected by default. Moving the launch to a new location however will place it elsewhere. Input a parameter other than “default” to change the location, and other beam parameters.
Choosing “View Launch” will plot the field amplitude of the launches. For the plot below, the third launch was removed.
Right-clicking on the structure will give the option to chose the “Combine Mode.” Be sure that Merge is selected to allow waveguides to combine.
When stringing multiple parts together, it is important to check a lightwave system for losses. BeamPROP Simulator, part of the Rsoft package will display any losses in a waveguide pathway. Here we have an example of an S-bend simulation. There appears to be losses in a few sections.
Here, the design for the S-bend waveguide has a few locations that are leaking, as indicated by the BeamPROP simulation.
The discontinuities are shown below, which are a possible source of loss:
After fixing these discontinuities, the waveguide can be simulated again using BeamPROP. In fact the losses are not fixed. This loss is called bending loss.
Bending loss is an important topic for wavguides and becomes critical in Photonic Integrated Circuits (PIC).
An interesting feature of BeamPROP simulations and other simulators in the Rsoft packages is that the simulation results can be displayed in a running animation. The following simulation is the result of a simulation of an optical fiber. BeamPROP simulates the transverse field in an animation as a function of the z parameter, which is the length of the optical fiber.
To design an optical fiber component with Rsoft CAD, select under 3D structure type, “Fiber” when making a new project.
To build a cylinder that will be the optical fiber, select the cylinder CAD tool (shown below) and use the tool to draw in the axis that the base of the cylinder is found.
Dimensions of the fiber can be specified using the symbol tool discussed previously and by right-clicking the object to assign these values. Note that animations of mode patterns through long waveguides is not only available for cylindrical fibers. Fibers may consist of a variety of shapes. Multiple pathways may be included. Simulations can indicate if a waveguide has potential leaks in it or the interaction of light with a new surface.
BeamPROP is a simulator found in the Rsoft package. Here, we will use BeamPROP to calculate the field distributions of our tapered waveguides. Other methods built withing Rsoft CAD are will also be explored.
The tapered waveguide that we are simulating is found below. We will use the BeamPROP tool to simulate the field distributions in the waveguide. We will also use the mode calculation tool to simulate the mode profile at each end of the waveguide.
BeamPROP Simulation Results
Mode Profile Simulation
The mode simulation tool is found on the sidebar:
Before choosing the parameters of the Mode Simulator, let’s first take a look at the coordinates of the beginning and end of the waveguide. This dialog is found by right-clicking on the component. The window shows that the starting point along the z axis is 1 and the ending point is 43 (the units are actually micrometers, by the way). We will choose locations along the waveguide close to the ends of the waveguide at z equals 1.5 and 42.5.
Parameter selection window:
Results at z = 1.5:
Results at z = 42.5: