Lecture 21 (EM21) -- Surface waves

This lecture introduces the student to the concept of surfaces waves. It describes why they exist identifies a number of different types of surfaces waves. Extra detail is provided on ways to couple energy into surface waves, surface plasmons, and Dyakonov surface waves.

[@mahmoudelzouka5689]

Prof. Raymond, I really appreciate your effort and your wonderful lecture slides. It helped me a lot through my PhD. I am a mechanical engineer by the way :)

[@empossible1577]

+Mahmoud El-Zoka Thank you!

[@takiyaazrin7562]

Great. Dr what is your field

[@hongbinbin24]

Thanks a lot for the video!

[@zeinabjafari5692]

really informative, thanks professor

[@empossible1577]

Thank you! Have you been to the course website? It has the latest version of all the notes along with other resources. emlab.utep.edu/ee5390em21.htm

[@msf60khz]

The radio surface wave, over sea water say, looks very much like a true surface wave, as we know there are ground currents and also a changeover frequency where the substrate changes from predominantly a conductor to a dielectric, rather like a metal. Will the wave be guided by the interface so it can follow a curve, or must we rely on diffraction? We see guiding action on a single wire transmission line, so why not with the Earth? The finite resistance of the substrate would seem to slow the wave within it a little, compared to the wave above. Would this cause the wave to be held down to the surface?

[@takiyaazrin7562]

Great explanation professor

[@empossible1577]

Thank you!

[@kalpanasinghsolanki1764]

Dear Sir In slide 31, you have explained why there is only Ex exists. I just want to make sure if I have understood correctly. If lower medium is metal, so electric field is zero in metal, it means Ex, Ey and Ez in metal are zero. we know at the interface only tangential components are equal, so Ey and Ez are zero in both the medium as Ey and Ez are zero in metal. But the perpendicular component Ex is discontinuous at the interface. So Ex is zero in metal but may be present in dieletcric ( upper medium). Is this correct what I have understood? Also, as the surface plasmons get excited only when the wave vector of the incident field matches with the surface plasmons. Here in the slide you have shown a decaying field in upper and lower field. But I have seen few papers, where surface plasmons are excited metal/insulator/metal/insulator layers just incident the plane waves. then how come do they matches the wavevector ? waiting for the reply. Thanks

[@LeilaMazaheri]

thanks for the video

[@empossible1577]

+Leila Mazaheri You are welcome!

[@LostAnFound]

27:15: Why do we, “kinda know that ahead of time?” regarding the need for metal?

[@empossible1577]

Even before EM analysis, it is usually pretty well known by most that metals are used to support surface plasmons. No worries if you were now aware of surface plasmons before this.

[@kalpanasingh7686]

I have one question. In slide 21, figure top left ( first figure), the representation of the wave in the upper half is blue and red blobs and in the upper half it is in the blue nad red straight lines. why it is so?

[@empossible1577]

To understand this, you need to understand what is happening physically. There is a wave being applied from the upper-left at some angle. When this wave hits the interface, some of it reflects and some of it transmits. This means that above the interface you have both the applied wave and the reflected wave. The "blobs" arise due to the interference between these two waves. In the bottom region there is only the transmitted wave so you see pure wave fronts that are flat. Hope this helps!

[@pratyushpushkar6343]

Prof.Raymond,you lectures are very nice and intuitive. However ,I have one doubt in slide 25.Here you have drawn reflectance vs frequency. It is possible that a lower order diffraction may get transmitted through Material 1 and 2 without coupling as a surface wave ,but still you may have a dip in reflectance vs frequency curve ,which may lead to a wrong conclusion.So,is their any other alternative technique to verify a surface wave?

[@empossible1577]

I suspect this could happen if you are not careful. You can calculate the number and angle of the diffraction orders using the famous grating equation. I would recommend ensuring there is only one diffracted mode to avoid the situation you described.

[@pratyushpushkar6343]

Thanks a lot sir

[@empossible1577]

You are very welcome!

[@chnadell1]

At about 32:30, it sounds like "nonmagnetic materials" have mu_r = 0. Doesn't nonmagnetic usually mean mu_r = 1? It seems like mu_r = 1 is the substitution necessary to arrive at the simplified dispersion relation at the bottom of the slide.

[@empossible1577]

+Christian Nadell Woops! Perhaps I misspoke. No magnetic response implies that the relative permeability is one, not zero.

[@josevellojin4465]

How do you make the images in 6:40 and 17:37?

[@empossible1577]

These are made using MATLAB's pcolor() and surf() commands. The data is generated from a simulation. If you want to learn a bit more about MATLAB graphics, checkout the videos in Topic 2 here: empossible.net/academics/emp4301_5301/ If you want to learn more about the simulation technique, which I think is the easiest to learn and implement, see this new book: empossible.net/fdfdbook/ Hope this helps!

[@ernaus22]

Can I download these slides from somewhere?

[@empossible1577]

Absolutely! In fact, I recommend accessing the course through the website. You can download the notes, get links to the latest videos, and get other resources: empossible.net/academics/emp6303/

[@wenda2192]

the Prism of Giza

[@kakistocracyusa]

This is remarkably devoid of any real understanding of physics. The aphysical causal relationships claimed (e.g, "because it's slower" "because it's compressed") are not supported by or based in any recognized physics. Light isn't "compressed" in a clad waveguide - that is contrived nonsense.

[@empossible1577]

The purpose of this video is to serve as an easy and intuitive introduction to surface waves and not to be a rigorous treatment of them. I suspect you were looking for the latter and came away disappointed. You make good points about how I describing the physics. This video comes after a series of other videos where I talk in more detail about phase velocity, group velocity, energy velocity, Bloch waves, electromagnetic properties of materials, etc. I recommend using the course website as your main portal to these videos as they puts in the sequence and context, you can download notes, get links to the latest versions of the videos, and get access to other learning resources. Here is the link to this course: empossible.net/academics/emp6303/