The spatiotemporal VCSEL model uses multimode laser rate equations in both frequency modes and transverse optical modes. There are a few of ways you could reduce the number of modes for examination:
- The most physical is to reduce the aperture size and thus the number of possible transverse modes will naturally decrease. You could adjust oxide aperture in the Geometry tab.
- You can use the Mode Selector component located in Receivers Library/Multimode. All the modes would still be used in the actual VCSEL calculation, but you now extracted the particular one of interest.
- Under the numerical tab of the Spatiotemporal VCSEL, you can select the number of modes to use in the calculation. This will introduce inaccuracies; as it then removes a number of modes from the multimode rate equations.
I have attached an example OptiSystem file which demonstrates each of the choices above. If you just want to examine particular modes arising from the system, I would recommend option 2.