On Thu, 15 Mar 2007, hb wrote:
I want to calculate the mode volume of a cavity. Could anyone tell
me how to calculate it using meep?
First, you have to decide what definition of modal volume you want to use.
For example, one definition that is relevant for the Purcell effect
(spontaneous emission) is:
V = integral epsilon |E|^2 / max epsilon |E|^2
but this is not the relevant definition for other physical processes, e.g.
chi3 nonlinear effects.
Second, whatever definition you use, you use Meep's
integrate-field-function and max-abs-field-function to compute it.
For certain definitions, there may be built-in Meep functions to help you
further. For example, there is a built-in function electric-energy-in-box
to compute integral epsilon |E|^2 / 2. There are also some functions in
the C++ interface that are available in the Scheme interface but ar enot
documented yet in the online manual.
For example, there is a function fields::electric_energy_max_in_box to
compute max epsilon |E|^2 / 2. There is even a function
fields::modal_volume_in_box that computes the volume V according to the
above definition. You would call it via:
(meep-fields-modal-volume-in-box fields (volume ...))
where (volume ...) is the volume in which to compute the integrals/maxima,
e.g. (meep-fields-total-volume fields) to just use the whole computational
volume.
Steven
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