Hi Hyma,
It's been a long time since I did this but this should be very easily
done if you choose each Bragg layer to have optimum optical thickness,
that is a quarter of a wavelength. Normalise the result to the lattice
spacing (as we pretty much always do in MPB) and you obtain
d(high)=n(low)/(n(high)+n(low)) where d(high) corresponds to the
thickness of the high index material normalised to the lattice. So the
only input parameters are n(high) and n(low).
Next, you just define a 1D unit cell of size 1 say in x with default
material n(low) which you fill with d(high), hence automatically
defining d(low). To "fill" with d(high) you can choose a cylinder with
axis x, infinite radius and height d(high). The code should be in one of
the examples downloaded with MPB I think...
Just add d(high) as input parameter if you want to define each
thickness, the rest is the same. You should get the result in no time.
Frederic
Hyma Yalamanchili wrote:
Hello
Iam trying to find bandgap for a 1 dimensional photonic crystal.(bragg
reflector structure)
I have many doubts in simulating the structure..
1.As Iam dealing with a 1 dimensional structure,how can I specify my
lattice vectors such that the structure repeats just in 1
direction.(i.e if crystal strucutre is periodic in x has to repeat in x
but not in y and z)..
If I specify no-size in y or z direction it doesn't consider y at all
but I have to specify a length in that direction without the lattice
repeating...
Attached is the code that Iam using.
Please help me
Thanks
Hyma Yalamanchili
----- Original Message -----
From: "F.S.F. Brossard" <[email protected]>
Date: Saturday, December 13, 2008 8:06 pm
Subject: Re: [MPB-discuss]
To: Hyma Yalamanchili <[email protected]>
Hi Hyma,
MPB does some internal dielectric averaging between boundaries so
that your structure look more realistic. It also means you probably
don't need such high resolution. For me, I rarely had to use a
resolution beyond 16 in x and y for all bandgap calculations. I
didn't see a significant difference with higher res (except a few
%). Also, you can lower your supercell size in z to 8, even for low
index material such as yours.
Howevever, you should increase your k-interp to 8 at least to make
sure you get a reasonably accurate bandgap.
Last advice: there is no need to calculate all points of the
reduced Brillouin zone to calculate the bandgap of a simple
triangular lattice with circular air-holes, at least for TE-like
modes (I have rarely looked at TM-like modes). In this last case,
just look at the K and M points of your first and second bands and
also at the intersection between the light cone and the G-K and G-M
directions.
Hope this helps,
Frederic
On Dec 12 2008, Hyma Yalamanchili wrote:
Hi Frederic
Attached is the control file which Iam using..
Thank u so much for your reply.
I hope my problem gets resolved
Hyma
----- Original Message -----
From: Frederic Brossard <[email protected]>
Date: Friday, December 12, 2008 1:13 pm
Subject: Re: [MPB-discuss] efield vs. dpwr, field definition -->
follow>up on old thread
To: Hyma Yalamanchili <[email protected]>
Cc: [email protected]
Hi Hyma,
Could you please let us know your control file? otherwise, it is
difficult to know why it takes so much time without asking you a
lot of
questions first.
Thanks,
Frederic
Frederic Brossard
Researcher
Cavendish Laboratory
J J Thomson Avenue
Cambridge CB3 0HE
Hyma Yalamanchili wrote:
Hii
Iam in the initial stages of learning MPB tool.
My work is mainly focused on band gap tuning.
I tried to change the radius every time before I simulate and
find the
band gap but as Iam dealing with 3-D structures,its consuming
a
lot of
time like 4 to 5 hrs for each simulation to run.
Can anybody suggest me a method to find the radius of the
triangular> lattice photonic crystal for a particular band gap
using some kind of a
loop???
Thanks,
hyma
----- Original Message -----
From: "Steven G. Johnson" <[email protected]>
Date: Thursday, December 4, 2008 12:01 pm
Subject: Re: [MPB-discuss] efield vs. dpwr, field definition -->
follow up on old thread
To: [email protected]
Your k point is wrong, for one thing. Maybe you're not
looking
at
a
band underneath the light line.
Look at the line-defect.ctl example file included with MPB.
Alternatively, you may find it easier to rearrange things
into
an
orthogonal supercell. See:
http://article.gmane.org/gmane.comp.science.photonic-bands/1376
http://article.gmane.org/gmane.comp.science.photonic-bands/1213
Steven (with a v)
On Dec 4, 2008, at 12:10 AM, Chad Husko wrote:
Stephen,
I spent a little more time with the fields and have some
follow
up
questions (on the bottom).
First, some answers to yours. I will be using the proper
definition
of the effective area as you suggest. I am sure that there
is
an
Ex
field. The propagation direction is x of the PhCWG. z is the
vertical super cell and y is the direction of sqrt(3)*a of
the
air
holes. Attached is the CTL file.
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_______________________________________________
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--
Dr Frederic Brossard
Researcher
Hitachi Cambridge Laboratory
Cavendish Laboratory
J J Thomson Avenue
Cambridge CB3 0HE
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