On Jul 11, 2008, at 10:41 AM, Yiling Qi wrote: > I am now simulating a 2D (square lattice) photonic crystal. I set k- > points to be Gamma-X-M. instead of the relationship between > frequency and parallel k-vectors, I am more concerned about the > propagation constant(generally named as beta, actually is z > component of wave vector in this situation I think). So how could I > convert frequency into kz? Could it be deduced by the formula shown > as follows: > beta^2=(2pi*f*n)^2-(2pi*kx)^2-(2pi*ky)^2 > ( suppose a=1 and f, kx, ky are all got from MPB) >
No, that formula is just for plane waves in a homogeneous medium. In general, there is no analytical formula relating frequency and propagation constant -- solving for this relationship (the dispersion relation) is the whole point of MPB. The propagation constant is just one component of the k vector. So, in MPB you are actually specifying the propagation constant and computing the corresponding frequency; to specify the frequency and compute the propagation constant, see this section of the manual: http://ab-initio.mit.edu/wiki/index.php/MPB_User_Reference#The_inverse_problem :_k_as_a_function_of_frequency Steven _______________________________________________ mpb-discuss mailing list [email protected] http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/mpb-discuss
