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: meep-discuss@ab-initio.mit.edu
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
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