Hi Ryan,
I can only offer some quick advice. First, I think you should try to
take the time to really understand what you're trying before you run a
simulation. Following the mailing list advice blindly won't help you
get farther.
You want to calculate the scattering of a 3D crystal slab. Your slab is
oriented in the XY plane, and propagation is in Z dimension.
What I think you want to try is to truncate your computation domain in
the Z dimension using PML layers. This creates the illusion that you
have infinite half spaces for waves to propagate in the +Z and -Z
directions, without having to actually simulate all that space.
Next, because your structure is an infinite and periodic slab plane, you
can truncate the compuation domain in the X and Y dimensions using
periodic boundary conditions. To do this, you have to choose a unit
cell which will correspond to your periodicity. With your hexagonal
lattice, this could correspond to a circle in the center of your cell,
plus four quarter-circles in the corners, for example.
In summary, PML in Z direction, periodicity in X and Y. For the latter
you will want (set-param k-point (vector3 kx ky 0)), with kx equal to
1/sx, and ky equal to 1/sy.
You can investigate whether your simulation is setup correctly by
visualizing the epsilon function. Your unit cell should like it could
tessellate into your full slab.
Best,
Matt
On Tue, 12 Aug 2008, Ryan Hao wrote:
> Hi, Matt,
>
> Sorry to trouble you, but I really need to work out this problem (I am
> in big pressure, my supervisor is hurry for my results everyday).
>
> My assignment is simple:
> Incident a pulse in to 3D photonic crystals slab, use 3D FDTD method
> to calculate the zodd transmission spectrum.
> My structure is shown in pic1~3.
> + + + + + + |y
> + + + + + |
> + + + + + + |_______X
>
>
> I was confused by Prof. Johnson, maybe I was too stupid:
> At first, I did not use Periodic Boundary Condition in my structure, he
> told me to use Periodic Boundary Condition in Y direction, add PML in X and
> Z directions
> On 07/08/2008, Steven G. Johnson <[EMAIL PROTECTED]> wrote:
>>
>> From a quick look at your structure, I would make two suggestions:
>>
>> First, if you want the transmission along a particular direction in the
>> slab, your computational cell should be periodic in the direction
>> perpendicular to the wave propagation. e.g. in your .ctl file the light is
>> propagating in the x direction, your cell should be periodic in the y
>> direction (no PML in y, only in x and z), and be only one period thick in
>> the y direction. That will make your calculations a lot faster! More
>> importantly, it will mean that your incident light (if your source is one
>> period wide in the y direction) will correspond to a specific incident
>> angle.
>>
>
> But yesterday he told me that I should only apply the Periodic Boundary
> Condition in X direction (the light propagate direction)
> On 12/08/2008, Steven G. Johnson <[EMAIL PROTECTED]> wrote:
>>
>>
>> If I recall correctly, only your X direction does not have PML. In
>> that case only the X component of k matters; the k component is set by
>> what direction you want your incident wave to come from. For normal-
>> incident light, kx=0.
>
>
> Now I really confused whether to add Periodic Boundary Condition in Y
> direction or not.
> For my understanding, I should not add periodic boundary in y direction in
> my structure, because the fields in the Y direction will decay and will not
> periodically repeat (though the structure are periodically repeat)
>
> Mr. Matt, please understand, I should finish the job in June, I am in big
> pressure every day.
> Further more, there must be other mistakes in my CTL file.
> Please, could you please so kind to have a look of the attached CTL files,
> and if possible, correct or point out the possible mistakes? (I attached
> both CTL with and without periodic boundary )
> I will great appreciate for your kind help~
>
> --
> ==============================
>
> Sincerely
>
> Yours,
> Ryan Hao
>
>
> PhD candidate
> Wuhan National Laboratory for Optoelectronics
> College of Optoelectronic Science and Engineering,
> Huazhong University of Science & Technology,
> Wuhan, 430074, P.R.CHINA
> Phone: 86-027-87792242-809(O)
> Website:
> http://www.wnlo.net/spm/People_Ryan_Hao.html
> http://wnlo.hust.edu.cn/spm/People_Group.html
>
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