# Discussion Forum

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## Reflectance / Transmittance calculation using PORT

Hello all

I want to calculate effect of nanostructure on reflectance and transmittance.

As a starting point, I have refered "Fresnel equation" library.
Without any nanostructure, the calculated reflectance is well matched with theorectical value!
So.. one thing I want to know is that the same port boundary condition can be applied to a model system with 3D nano structure? (Simply, air/Nanostructures on substrate/substrate)

Also, I want to calculate the reflectance using input and output power.
Output power can be calculated using integration of time-averaged power outflow (nPoav).
However, I don't know how to know incident power when I use scattering boundary condition, or electric field condition.
Would you comment on this?

<Summary>
1. Using same model of "Fresnel equation" library, can reflectance of a system with 3D nano structure be calculate?
2. How can I calculate incident power of light, when I use electric field boudnary condition?

Thanks!

Dong-yeong Kim

5 Replies Last Post 2013年6月18日 GMT-0400上午2:50
Posted: 5 years ago
1. Yes, generally
2. Electric field BC won't give you the correct solution. Only scattering BC will work.

Posted: 5 years ago
Thanks sir.

I wanna ask you 3 more things.

1. As far as I know, there are 3 ways to generate electric field.
- Scattering boundary condition
- Electric field
- Port
Could you explain the differences between them?

2. Many libraries are using Floquet periodicity for imposing periodic boundary condition.
In my humble opinion, effect of "Floquet periodicity option" and "Continuity option" might be same.
Is it right?

3. For periodicity, PEC(PMC) condition can be used when electric(magnetic) field is normal to surface.
So.. if field is not perpendicular to a certain surface, I should use a periodic condition instead of PEC/PMC.
Is it also right?

I have had difficulty choosinig boundary conditions. :(

Posted: 5 years ago
1. Electric field BC - you simply specify total electric field at the boundary. Since you generally don't know the reflected field, you can't use it
Scattering BC - to launch plane waves
Port BC - to launch plane waves as well as any other. As a benefit, reflection coefficients are calculated for you.

2. Floquet BC is more general since it takes care of phase shift at the boundary. Continuity BC doesn't.

3. No. You should use Floquet. I'd suggest using it always, even when PEC/PMC would work.

Posted: 5 years ago
Thanks a lot!

This is a big helpful to me.

Posted: 4 years ago

Hello all

I want to calculate effect of nanostructure on reflectance and transmittance.

As a starting point, I have refered "Fresnel equation" library.
Without any nanostructure, the calculated reflectance is well matched with theorectical value!
So.. one thing I want to know is that the same port boundary condition can be applied to a model system with 3D nano structure? (Simply, air/Nanostructures on substrate/substrate)

Also, I want to calculate the reflectance using input and output power.
Output power can be calculated using integration of time-averaged power outflow (nPoav).
However, I don't know how to know incident power when I use scattering boundary condition, or electric field condition.
Would you comment on this?

<Summary>
1. Using same model of "Fresnel equation" library, can reflectance of a system with 3D nano structure be calculate?
2. How can I calculate incident power of light, when I use electric field boudnary condition?

Thanks!

Dong-yeong Kim

I am a newbie in this field. I want to obtain reflectance and absorption spectra for a substarte. Can you tell me which module to use..?? Probably some link which gives step by step guidance.. ?

Thanks

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