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What is the exact electric field expression when using the PORTs? - Inconsistent values

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Dear all,

In the attached 2D model, I use 'Electromagnetic Waves frequency domain' and I would like to study the light propagation inside my structure.

I would like to have a input power flow at port 1 of 100 mW/cm^2, the excitation must be a TE plane wave. My geometry is also periodic, therefore I have imposed the periodic boundary condition and used 2 periodic ports.

As you can see from the model the excitation at port one is Pin = inputPower = 100 [mW/cm^2] * Active_area, where Active_area is the active area of my device (Active_area = width * depth, however depth is just an ideal depth since this is a 2D model).

In order to have a TE polarized wave, I have defined the following 'Electric field amplitude' in port1: E0 = [ 0 0 1]. I don't understand why they call it 'Electric field amplitude', because this field seems to be a 'versor'. No matter what values you put in the z term, if you write E0 = [0 0 1e10] the calculated electric field in my structure would be the same.

SO, DO YOU KNOW WHAT IS THE EXPRESSION OF THE FIELD EXCITED BY PORT1? I cannot find it in the guide.

There is also another issue. I have placed a point probe PowerFlowPoint in the middle of port1. This point probe
probes a ‘powerFlow’ (amplitude of the Poynting vector) of 5.58355 [W/m^2] at the port 1. However at port 1 I have a Port input power of Pin = inputPower = inputPowerFlow*Active_area = 1e-6 W. The power flow corresponding to Pin is inputPower/Active_Area = 100 [mW/cm^2] = 1000 [W/m^2].

HOW WOULD YOU EXPLAIN THIS INCONSISTENCY in the values?

Thanks in advance,

Samuele


3 Replies Last Post 20 janv. 2013, 00:21 UTC−5
Sergei Yushanov Certified Consultant

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Posted: 1 decade ago 18 janv. 2013, 12:09 UTC−5
Samuele,

Your result is the same because there is no incident wave in your model.

For TE polarization, equation for the plane incident wave is
E={0, 0, E0*exp(-j*k.r)}

where

k={kx,ky,0} is wavevector and r={x, y, 0} is spatial radius-vector.

Look at the fresnel_equation.mpg from Comsol RF Model Library.

Regards,
Sergei
Samuele, Your result is the same because there is no incident wave in your model. For TE polarization, equation for the plane incident wave is E={0, 0, E0*exp(-j*k.r)} where k={kx,ky,0} is wavevector and r={x, y, 0} is spatial radius-vector. Look at the fresnel_equation.mpg from Comsol RF Model Library. Regards, Sergei

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Posted: 1 decade ago 18 janv. 2013, 15:10 UTC−5
When you specify the electric field in port boundary condition, you just give the direction. The value of electric field will depend on the input power. If you need just TE wave, instead of using "user defined" port, just use rectangular.

Regarding the point probe, you better not use it for calculating power flow. Since power is defined as W per unit area, it's hard to tell what the area of your point probe is ;)
When you specify the electric field in port boundary condition, you just give the direction. The value of electric field will depend on the input power. If you need just TE wave, instead of using "user defined" port, just use rectangular. Regarding the point probe, you better not use it for calculating power flow. Since power is defined as W per unit area, it's hard to tell what the area of your point probe is ;)

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Posted: 1 decade ago 20 janv. 2013, 00:21 UTC−5
Thanks both. It makes more sense now! ;-)
Thanks both. It makes more sense now! ;-)

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