This page provides a simple analysis group that calculates the net power flow out of a rectangular volume within a simulation. The files in this section were created using FDTD, but the same analysis group can be found in the Component library in MODE.
Lumerical provides many built in analysis groups in our object library. Please press this button to open the online library of analysis groups and select optical power category to insert transmission boxes.
The monitor group in the associated files (usr_transmission_3Dbox.fsp and usr_transmission_2Dbox.fsp ) calculates the net power flow out of the box of monitors. To use this group to calculate net power flow into the box, just multiply the result by -1.
For example, in the associated files, we have a small silicon particle in a focused beam. The box of monitors can be used to measure the power absorbed by the particle. After running the simulation, use the following commands to plot the absorption vs wavelength. Once the visualizer is open, you may want to use the "-Real" option to make the numbers positive, since power is flowing into the box.
net_power = getresult("trans_box","T");
These monitor boxes work properly when symmetry boundary conditions are used. When symmetry boundary conditions are used, the monitor group assumes there will be equal power flows on both sides of the plane of symmetry.
Note: Field data not saved
The monitors in these groups are set to record the net power only, to minimize the amount of data saved to file.
Note: Spherical transmission monitors
The files usr_transmission_3Dsphere.fsp and usr_transmission_2Dsphere.fsp contain spherical transmission monitor objects. These are very similar to the transmission boxes described above, but they use a series of point monitors to create a spherical surface, rather than using 6 2D monitors to create a box.
Due to the additional interpolation required by these monitors, they tend to be less accurate than box monitors. They are also not designed to work with symmetry boundary conditions and can't be used to do far field projections. For these reasons, we recommend using box monitors rather than spherical monitors.