help in FDTD for calculating propagation constant

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red5000

Joined: 06 Nov 2006
Posts: 120
Helped: 32

01 Dec 2008 16:41 propagation constant

i'm looking for any program to calculate the propagation constant with FDTD, and thanks

red5000

Joined: 06 Nov 2006
Posts: 120
Helped: 32

08 Dec 2008 18:44 waveguide fdtd

help me, any adeas please.

rrumpf

Joined: 06 Jul 2007
Posts: 179
Helped: 22

23 Dec 2008 22:20 fdfd waveguide

I maybe do not quite understand what you are asking. Do you want to calculate the propagation constant of a waveguide mode? If so, is there a reason you want to do this with FDTD? I would suggest looking at a frequency-domain tool like the finite element method (FEM) or finite-difference frequency-domain (FDFD). A frequency-domain code can very easily solve an eigen-value problem where the eigen-values are your propagation constants. What type of waveguides are you interested?

I will keep this e-mail short incase I do not understand what you are interested in.

-Tip

red5000

Joined: 06 Nov 2006
Posts: 120
Helped: 32

27 Dec 2008 15:34 numerical values for propagation constant

my professor require to me to use the fdtd method for calculate the beta (propagation constant), and the waveguide is a finline.

rrumpf

Joined: 06 Jul 2007
Posts: 179
Helped: 22

27 Dec 2008 16:18 waveguide fdtd

Calculating the propagation constant (beta) of a guided mode using FDTD works backwards from what you may be thinking. Instead of FDTD giving you beta, you will give FDTD the beta quantity and it will compute the modes that result. Essentially, you will iterate this method until the mode you are interested in falls onto the frequency you are interested in. The algorithm works like this:

1. Pick a beta
2. Run 2D FDTD with d/dz=i*beta
3. FFT the time response
4. Look for peaks in the FFT. These are your modes
5. The beta you assumed is the beta of the mode you just calculated.
6. Adjust your beta and rerun FDTD until the frequency of the mode is the frequency you are interested in.

Here are two references:

Min Qui, "Analysis of Guided Modes in Photonic Crystal Fibers Using the Finite-Difference Time-Domain Method," Microwave and Optical Technology Letters 30(5), pp. 327-330 (2001).

T. Ando, "Eigenmode Analysis of Optical Waveguides by a Yee-Mesh-Based Imaginary-Distance Propagation Method for an Arbitrary Dielectric Interface," J. Lightwave Technol. 20( Cool

, pp. 1627-1634 (2002).

red5000

Joined: 06 Nov 2006
Posts: 120
Helped: 32

27 Dec 2008 20:52 propagation constant beta

thank you for your help, do you have any pattern program for beggening.

rrumpf

Joined: 06 Jul 2007
Posts: 179
Helped: 22

27 Dec 2008 20:58 how to calculate mode in fdtd

I do not have these codes, but I am interested in writing one for modeling very large waveguides. If/when I do, I would be happy to share my code.

-Tip

red5000

Joined: 06 Nov 2006
Posts: 120
Helped: 32

28 Dec 2008 10:14 how to find modes in 2d fdtd

thank you, and if you have e-books in this domain could you please help me with it.

Added after 5 minutes:

and could you please upload the two papers of qiu and ando.

rrumpf

Joined: 06 Jul 2007
Posts: 179
Helped: 22

13 Jan 2009 0:53 propagation constant beta for a waveguide mode

Here are three papers...

Unfortunately, I don't have any e-books.

-Tip

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elifelite

Joined: 12 Apr 2006
Posts: 46
Helped: 14

13 Jan 2009 12:45 calculating propagation

rrumpf wrote:

Hi,

Can you please explain how to find propagation constant solving eigen value problems with FEM? Or any references that you advise?

thanks

rrumpf

Joined: 06 Jul 2007
Posts: 179
Helped: 22

13 Jan 2009 13:13 optiwave fdtd

solving an eigen-value problem with FEM is easier and harder. It is harder in the sense that FEM requires more upfront work formulating the equations you type into the computer to build the matrices. It is easier in the sense that once you have the matrices, you can simply solve for the eigen-values (propagation constants) and eigen-vectors (the mode profiles) and the answers fall right out.

What type of waveguide are you analyzing? If you are just starting out, can I recommend a frequency-domain finite-difference method?

For a good ebook on numerical modeling, try this...

http://rapidshare.com/files/14651218/numerical.methods.in.electromagnetics.rar.rar

-Tip

elifelite

Joined: 12 Apr 2006
Posts: 46
Helped: 14

13 Jan 2009 15:29 fdtd of waveguide

rrumpf wrote:

Hi,

Thanks for the book, I've already started to study photonic crystal waveguide with FEM. So now dont have chance to do this with FDTD.

red5000

Joined: 06 Nov 2006
Posts: 120
Helped: 32

13 Jan 2009 21:43 how to find propagation constant

thanks

khald_1980

Joined: 11 Dec 2007
Posts: 12
Helped: 1
Location: libya

22 Jan 2009 13:49 optiwave fdtd rapidshare

you can try use optiwave fdtd to find every thing aboutv guiding mode in photonic crystal waveguide

good luck Very Happy

rrumpf

Joined: 06 Jul 2007
Posts: 179
Helped: 22

22 Jan 2009 15:19 waveguide propagation constant

Does Optiwave FDTD have a way to distinguish degenerate modes? That is, can it separate distinct modes that happen to have the same propagation constant?

red5000

Joined: 06 Nov 2006
Posts: 120
Helped: 32

23 Jan 2009 9:43 fdtd fdfd

i don't know what is Optiwave FDTD ??

Added after 8 minutes:

but i'm looking for an algorithm with fdtd

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iyami

Joined: 12 Apr 2008
Posts: 120
Helped: 16

23 Jan 2009 13:58 value of propagation constant

Quote:

i don't know what is Optiwave FDTD ??

A commercial FDTD simulation tool. Usually, sold with special hardware.

red5000

Joined: 06 Nov 2006
Posts: 120
Helped: 32

31 Jan 2009 9:45 optical waveguides: numerical modelling with fdtd

help

Last edited by red5000 on 02 Feb 2009 16:47; edited 1 time in total

red5000

Joined: 06 Nov 2006
Posts: 120
Helped: 32

02 Feb 2009 16:46 how to find propagation constant in waveguide

i'm looking for an algorithm with fdtd please

rrumpf

Joined: 06 Jul 2007
Posts: 179
Helped: 22

02 Feb 2009 17:02 fdtd optiwave

Unfortunately, I have not written this form of FDTD. You may look for codes that go along with Taflove's book on FDTD, but I do not know if you will find it there. If not, you have three options: (1) you can purchase an off-the-shelf software; (2) you can pay somebody to write the code for you and provide you the code; or (3) be satisfied with a different modeling approach like FDM or EM where codes are available online. I suspect in these tough economic times, there would be plenty of individuals willing to write the code for you.

-Tip