Whoops, better revise that source declaration as:
(set! sources
(list
(make source
(src
(make gaussian-src
(width df)
(frequency fcen)))
(component Ex)
(amplitude 2)
(center 0 0 (- (/ sz 2) dmpl))
(size sx sy 0))))
We don't want the source sitting completely inside the PML!
Regards,
Alex
____________________________________________________________________
Alexander S. McLeod
B.A. Physics and Astrophysics - University of California at Berkeley
Simulation Engineer - Theory Group, Molecular Foundry (LBNL)
Site Lead - Network for Computational Nanotechnology at Berkeley / MIT
[email protected] 707-853-0716
____________________________________________________________________
On Dec 2, 2009, at 3:54 PM, [email protected]
wrote:
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Today's Topics:
1. Re: plane wave sources in meep (Alex McLeod)
From: Alex McLeod <[email protected]>
Date: December 2, 2009 3:54:43 PM PST
To: [email protected]
Subject: Re: [Meep-discuss] plane wave sources in meep
Hi Philip,
In my experience, the best way to get an ideal plane wave source in
MEEP for simulations like scattering off a nanoparticle is the
following: Place PML layers around the entire computational cell,
and place a plane source along one of the inner PML boundaries.
Make sure the size of the source is the same as that of the ENTIRE
simulation cell (including the PML thicknesses) along its planar
dimensions. For example:
(set! (geometry-lattice (make lattice (size sx sy sz)))
(set! pml-layers (list (make pml (thickness dpml))))
(set! sources
(list
(make source
(src
(make gaussian-src
(width df)
(frequency fcen)))
(component Ex)
(amplitude 2)
(center 0 0 (/ sz 2))
(size sx sy 0))))
When I've instead used "(size (- sx (* 2 dpml)) (- sy (* 2 dpml))
0)" for the source, the results have less than ideal due to discrete
dipole effects at the source edges propagating into the simulation
cell. This even seems to be an issue when periodic boundaries are
used. That said, my prescription is not perfect - there is a
gradual decrease in source intensity as the wavefront moves down the
simulation cell due to PML absorption at the boundaries, but the
effect is typically small, especially when sx ~ sz and sy ~ sz.
Give that setup a whirl and let me know if you notice problems with
it.
Cheers,
Alex
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