Is it possible to perform adjoint inverse design through the Poynting Flux over a certain range of frequencies? The meep.adjoint.EigenmodeCoefficient object has a register_monitors function to track the power across specified frequencies, but I'm unsure as to how one could use this to inverse design a device.

I tried to use it in this tutorial, where I added the following lines in the adjoint optimization tutorial:

frequencies = np.linspace(1/1.55 - 0.1, 1/1.55 + 0.1, 100)
TE_top.register_monitors(frequencies)

https://nbviewer.jupyter.org/github/NanoComp/meep/blob/master/python/examples/adjoint_optimization/01-Introduction.ipynb

I replaced the TE0 variable with TE0.monitor, but this ended up giving me the following error:

AttributeError: 'DftFlux' object has no attribute 'register_monitors'.