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Electric field

Posted 31 janv. 2022, 06:32 UTC−5 2 Replies

Francesca Cattai
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Hello everyone, I am new in comsol. For my thesis I need to observe the propagation of the electric field emitted by an UVC led. In particular, we don't want to reconstruct the photodiode but simply to say to comsol that a spherical wave of initial amplitude E0 note starts from a given surface. How can I do that?

2 Replies Last Post 3 févr. 2022, 10:50 UTC−5
Robert Koslover Certified Consultant
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Posted: 3 years ago 31 janv. 2022, 15:42 UTC−5
Updated: 3 years ago 31 janv. 2022, 15:52 UTC−5

If you truly wish to simplify the problem to the extent that all the physics of interest to you can be modeled as a "spherical wave" (which, we note, for EM waves, does not really exist in nature) with some initial (presumably scalar?) amplitude , then it seems to me that you don't need to build a Comsol model at all. Set and plot E vs. r, for various values of t. Note that , , and is the radius of your spherical source. As you can see from the equation here, when and . E falls off linearly with 1/r, just as it should, while also oscillating appropriately in time and space. Did you, perhaps, want to include a more detailed view of the actual physics of your source than that? Note that if you don't care about polarization, you could simply set a boundary condition (let in the equation for E above) on a spherical surface in a Comsol model using the classical scalar wave equation. This is included in all Comsol packages. Go to File, New, Model Wizard, 3D, Mathematics, Classical PDEs, and then Wave Equation (waeq).

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If you truly wish to simplify the problem to the extent that all the physics of interest to you can be modeled as a "spherical wave" (which, we note, for EM waves, does not really exist in nature) with some initial (presumably scalar?) amplitude E_0, then it seems to me that you don't need to build a Comsol model at all. Set E=E_0(r_0/r)cos(k(r-r_0)-\omega t) and plot E vs. r, for various values of t. Note that k=2\pi/\lambda, \omega = 2\pi f, and r_0 is the radius of your spherical source. As you can see from the equation here, E=E_0 when r=r_0 and t=0. E falls off linearly with 1/r, just as it should, while also oscillating appropriately in time and space. Did you, perhaps, want to include a more detailed view of the actual physics of your source than that? Note that if you don't care about polarization, you could simply set a boundary condition (let r=r_0 in the equation for E above) on a spherical surface in a Comsol model using the classical scalar wave equation. This is included in all Comsol packages. Go to File, New, Model Wizard, 3D, Mathematics, Classical PDEs, and then Wave Equation (waeq).
Francesca Cattai
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Posted: 3 years ago 3 févr. 2022, 10:50 UTC−5

Thank you very much for the support, I will try to do what you advised me, hoping to succeed. Greetings Francesca

Thank you very much for the support, I will try to do what you advised me, hoping to succeed. Greetings Francesca

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