On Jun 5, 2008, at 7:47 AM, Juntao Xi wrote: > > -------------------------------------------------- > From: "Steven G. Johnson" <[EMAIL PROTECTED]> > Sent: Thursday, June 05, 2008 9:16 PM > To: <[email protected]> > Subject: Re: [Meep-discuss] E and H for the "same point" > >>> >>> Both E and H are necessary in order to calculate stress tensor. >>> Do I need to run the simulation twice with different source >>> component? >> >> No. A single source produces both E and H. (From Maxwell's >> equations, an oscillating E field creates H fields and vice versa.) > > However, all Hx and Hy field are zero when src-component is set as Ey. > all Ex and Ey field are zero when scr-component is set as Hxuss
In two dimensions, the fields (by symmetry since the xy plane is a mirror plane) can be divided into two polarizations, TE (Hz, Ex, Ey) and TM (Ez, Hx, Hy). When you use an Ey source, it only produces TE- polarized fields. You get a magnetic field (and a nonzero stress tensor), but it is in the z direction only. Conversely, an Hx source produces only TM fields, by symmetry. (See also chapter 3 of our new textbook, available online at http://ab-initio.mit.edu/book) Obviously, the optical forces (the stress tensor) will depend on what source you use (and consequently what field patterns you excite). I have no idea what physical situation you are interested in. However, there is nothing physically wrong with using just a TE source, computing the stress tensor from the resulting (Ex,Ey,Hz) fields, and hence obtaining the radiation pressure on some object. Steven _______________________________________________ meep-discuss mailing list [email protected] http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
