Lecture -- Unit Cells & Brillouin Zones

[@alirezasadeghifar3815]

Perfect explanation, I have finally learned the Brillouin zone in depth.

[@stopstalkingyouspookybastard]

oh trust me, this is just scratching the surface. in depth this shit is way too fucked up

[@blackmagicsuiteopus9545]

@@stopstalkingyouspookybastard hahaha naah. It is related to very complex stuff but the concept itself is not that hard, don't you think?

[@dutonic]

@@stopstalkingyouspookybastard Seeing this at the start of my graduate condensed matter physics class. Don't scare me like that!

[@jacobvandijk6525]

@ 1:54 "A PERIOD"??? A period is an amount of time. This is an amount of space. For the last few ceinturies. this is a called WAVE LENGTH.

[@empossible1577]

The word “period” is a homonym, meaning it has multiple definitions. It can mean the duration of time for one cycle of a wave to repeat, but it can also mean the physical distance over which a periodic pattern repeats. In the case you pointed out, we are not talking about waves at all. Instead, we are talking about periodic structures, or lattices, such as photonic crystals or metamaterials. Think of patterns like Swiss cheese, fishnets, checkerboards, etc. These are physical structures and not waves all. They do not move or change with time. The distance between repetitions of the pattern is called the period (another definition of the word), or alternatively periodicity, lattice period, lattice spacing, and probably other things. Because we are not talking about waves here, the repetitions are described by a ‘grating vector’ instead of a ‘wave vector.’ There is a close analogy between the two which has a profound effect in the mathematics describing waves propagating through periodic structures. If you want more evidence or more information about this, perform a Google search for "period of a lattice."

[@jacobvandijk6525]

@@empossible1577 When I teach, I try to be as clear asl possible about the words or concepts I use. I don't want students/viewers to be confused. Thanks for your reaction anyway.

[@empossible1577]

@@jacobvandijk6525 I do as well. I think part of the problem is that you are viewing the third video in a series of videos on periodic structures. In a prior video, I have pictures describing exactly what I mean by "periodic structure" and definitions of words. I recommend using the course website as your main portal to these videos. You can see the organization of the videos, download the notes, and get links to many other learning resources. Here is the course website: empossible.net/academics/21cem/ The video you are watching is the third video in Topic 4.

[@macmic1097]

Golden video on this topic 👍👍👍👍 This video should have million views

[@mohammadmahyaresfahani2905]

Your video was very clear and proffessional. Thanks!

[@empossible1577]

Thank you!

[@luisriverafernandez8652]

Thank you very much for this great explanation of Brillouin zones.

[@empossible1577]

Thank you! Great to hear it is helping people!

[@JulianFrey-b1g]

Great Video !!!

[@relaxinghealingmusic6541]

your channel needs more attention man. keep it up. nice explanation

[@empossible1577]

If you know how to get it more attention, I am listening! Thank you!

[@relaxinghealingmusic6541]

@@empossible1577 Man, see my channel, its sucks.. what advice can I give you, however, will share your content with others. Cheers!

[@146fallon]

I wish I have watched this video earlier. Thank you for the video. Self-Studying by KZbin is as taking many redundant paths to understand a thing.

[@empossible1577]

Thank you!! It is great to hear the content is helping!

[@melvi8834]

8:11

[@zihengwang7048]

a great tutorial, very helpful

[@leonbaiyu]

Great explanation thogh I enjoyed the pronunciation of Brillouin zone much less 😅

[@dana5731]

Great!! ❤

[@physicsdiva1871]

Nice explanation

[@kevinpears2628]

Excellent sir

[@fabio_air4230]

Your lectures are clear and engaging! Could you provide some literature about the use of "pseudo-periodic" in electromagnetics and/or acoustics?

[@empossible1577]

Thank you! I am not actually sure where that boundary condition is discussed in the literature. I have a book that should get released around January where I cover the boundary condition in detail, including its derivation. Here is a link to what will be the book's website: empossible.net/fdfdbook/

[@serhaterdogan6490]

Great video! I wish you had a list where you put lectures in order so that it is easier to follow. You have a lot of videos but I am having trouble navigating through them.

[@empossible1577]

You got it! I recommend accessing the courses through the official course website. I keep all of them here: empossible.net/academics/ The specific video you are watching here is in Topic 4 of the EM21 course at the link below: empossible.net/academics/emp6303/ Hope this helps!!

[@serhaterdogan6490]

@@empossible1577 Thanks for the quick reply! This helps a lot

[@mfaisal654]

Dr. Rumpf! Thanks for a very well-explained lecture. I wonder you categorize FSS and metamaterials separately. Materials with negative material parameters also act as frequency selective surfaces. Is the phenomena behind filtering in case of MNG & ENG materials similar as it is in DPS materials. In my understanding, there is LC circuit behavior which enables bandpass and bandstop filtering in DPS materials.

[@empossible1577]

Most everything electromagnetic has a filtering response, but we do not label them all as FSSs. An FSS is a flat planar structure that filters. Metamaterials, gratings, photonic crystals, circuit elements, etc., can all also perform filtering functions, but they are not FSSs. It also does not make much sense to assign effective permeability and permittivity to planar structures. That is more for volumetric things like metamaterials. Generally metamaterials are subwavelength so the wave does not diffract inside of the structure. Photonic crystals have a slightly larger period making them diffract. There are also high impedance planes, artifical magnetic conductors, metasurfaces, metalines, etc., The line between all of these different things is very gray and fuzzy. As long as you understand how all the devices are working, I would not get too paranoid about what you call them. Generally, we call things whatever will get the research funded. ha ha

[@astrophage381]

Thank you Dr. Rumpf!

[@empossible1577]

You are welcome! Glad the material is helping you!

[@rabiulislamsikder344]

Dear Prof., Could you make a video on the photonic crystals?

[@empossible1577]

Absolutely! I recommend accessing the videos through the official course website. Here is the link: empossible.net/academics/emp6303/ Lecture 5c is about photonic crystals, but all of the lectures in Topic 4 and 5 lead up to lecture on photonic crystals. Hope this helps!

[@rabiulislamsikder344]

@@empossible1577 Thanks

[@tarunpurohit6522]

Brilliant

[@aiyshafayaz6682]

Thanks a lot sir.

[@empossible1577]

You are welcome!

[@oddly-satisfying666]

helps a lot. thanks.

[@empossible1577]

You are welcome! I recommend accessing the videos through the course website. You can download the notes and the links will always point to the latest versions of the videos: empossible.net/academics/emp6303/

[@sollinw]

supergood!

[@haya4895]

thank you so!

[@nadzimzamri2149]

This is great. But in my honest opinion, you dont need to put 'typed sentence or statement' in the presentation if you not gonna read it out loud. I'm kinda lost to keep track on listening to your voice while at the same time trying to read those typed sentences. You get what I mean?

[@empossible1577]

I definitely agree that these are horrible slides for something that is purely a presentation. However, that is not what is happening here. These have been converted to PDF and are intended to be notes for a course that I teach. Therefore, they have to be somewhat stand-alone in this regard and have enough information in them that I do not need to be narrating them. Here is a link the course website: empossible.net/academics/emp6303/ BTW, here is a link to one that I intended to only ever be presented so there is MUCH less text. It is an introduction to all of electromagnetics for high school seniors and college freshmen. That was a pretty challenging thing to do. kzbin.info/www/bejne/haO3o5yKgr94pM0

[@nurnasuhakassim3207]

Okay bro 🌚👌🏻

[@Marco-x3c]

Bro its 2am how the fuck did i end up heee

[@empossible1577]

Luck!