Yes, you are right: “Inverse design using Topology Optimization enables automatic generation of devices that are optimized for a user-specified figure of merit (FOM). In this Y-splitter example, we want to maximize T_up, the fraction of the total input energy that is transmitted into the upper arm. Since we will enforce symmetry in the y-direction, the maximal value of the FOM will be 0.5. For visualization, instead of directly plotting T_up, we show the insertion loss, so FOM=0.5 – T_up.”
Currently the optimization is to target a scalar result, which means it has only one value.