Steven G. Johnson <stevenj.mit <at> gmail.com> writes:

> > > > On Jul 14, 2009, at 11:08 AM, Alexandre Besnier wrote: > Good morning, I'm a student and I work currently on your software Mpb, I try to make a rectangular lattice of 0.204µm x 0.561µm size, and I would like to understand units give by band diagram. On your wiki pages you say that frequency is given in c/a unit, but I don't understand several things : - In band diagram, if I obtain frequency = 1, that say a=c, ie a=3.10^8 meters ? > > > No, it means that frequency = 1 (c/a). Since frequency = c / lambda, this means that > > > c/lambda = 1 (c/a) > > and thus > > > lambda = a > > > Put another way, the frequency in MPB's units is exactly the same as a/lambda (where lambda = vacuum wavelength). > > - Normally, "a" is the lattice period, but with rectangular lattice, I have two periods, so what is "a" compared with my two periods ? > > "a" is whatever unit of distance you want; it doesn't have to have anything to do with the lattice constant(s). > > You are perfectly free to use a=1um, for example, and then specify the size of your computation cell as 0.204 x 0.561, and give all distance units in microns. In this case the frequencies returned by MPB are equivalent to 1/(lambda in microns). > > - In the page "Mpb User Tutorial/A few words on units", you say at the last paragraph : "Thus, the corresponding vacuum wavelength is a over the frequency eigenvalue." It is not "Thus, the corresponding vacuum wavelength is c over the frequency eigenvalue." ? Because frequency * lambda = c ? > > See above. This is a consequence of using c/a units of frequency. > > | Finally, if I would like to have frequency in Hz, what I have to do to convert it ? > > Multiply Meep's units by c/a in SI units. > > > Steven > > > > > _______________________________________________ > mpb-discuss mailing list > mpb-discuss <at> ab-initio.mit.edu > http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/mpb-discuss Hi Professor Steven G. Johnson I am trying to simulate the rectangular rods in rectangular lattice and facing difficulty in the process. I am not sure how to set the rectangular rods length in program as in book it is mentioned for square rods in sqare lattice that square side has a relation as side/a=0.4(as an example) but how can we apply it for the case rectangular rods in rectangular lattice. For example my dimensions for rectangular rod and rectangular lattice are x1 x y1 and x2 x y2 then what will be my inputs in program. Thanks _______________________________________________ mpb-discuss mailing list mpb-discuss@ab-initio.mit.edu http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/mpb-discuss