What is an evanescent wave? What are its applications?

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Evanescent waves are closely related to near-field effects and arise from the application of Maxwell's Boundary Conditions, though deriving them mathematically can be complex. The discussion highlights the challenges faced in understanding and applying these concepts, particularly in scenarios like fiber networks. Participants express a desire for a step-by-step proof of how evanescent fields can be derived from Maxwell's equations. Additionally, resources are shared for further reading on the topic, including presentations and reviews in both English and German. The exploration of evanescent waves remains a nuanced area of study in electromagnetic theory.
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I am reading some papers that mention evanescent waves. From what I can find, evanescent waves occur because of the Maxwell Boundary Conditions but I don't really see how. Could some please comment on this or just on the general topic. Thanks!
 
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ksmith1281 said:
I am reading some papers that mention evanescent waves. From what I can find, evanescent waves occur because of the Maxwell Boundary Conditions but I don't really see how. Could some please comment on this or just on the general topic. Thanks!

That's a nice question. Evanescent fields are near field effects which are not easy to deal with. We had struggled to derive evanescent fields from Maxwell Equations to solve a problem in an hypothetical fiber network a while ago and I assure you it's not an easy task to mathematically immerse into evanescent phenomena. For general information and some of the applications ; http://www.faculty.iu-bremen.de/dknipp/c320352/Projects/Presentations%202005/CL%20Evanescent%20Fields.pdf

I would like to hear if someone comes up with the proof that derives evanescent fields from Maxwell equations step-by-step.
 
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Thanks!
 
For those who understand German, here I've written a quite complete review about fields in wave guides (in vacuo):

http://theory.gsi.de/~vanhees/faq/causality/node8.html
 
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