Finding mode volume with python interface

[Dev-linkon]

Hi there,

I want to simulate a photonic crystal cavity wthere the ratio of quality factor and the mode volume (Q/V) is very important. By running the simulations for resonant modes with 'Harminv', I am able to obtain the Q but I can not obtain any information about V.

Kindly help me with the Python script to find out the mode volume (V).

Thanks for reading

[stevengj]

Realize that Q/V is simply an approximation for the LDOS at the point of maximum field intensity, so I would generally recommend computing LDOS instead. Meep has a built-in dft_ldos feature to help with that, and the Meep LDOS tutorial has an explicit comparison with Q/V.

See this textbook chapter, section 4.4.6, and also this paper on cavity optimization.

Alternatively, if you want to compute the modal volume directly, then you need the E field pattern of the mode. The easiest way to get this, after you have already run harminv to find the resonant mode frequencies, is to run a new simulation with a narrow-band source around the resonant frequency (so that you excite only the mode). After the source is done, the E field should be approximately that of the mode, and then you can use the modal-volume formula with this.