Lecture -- Other Waveguides

This short video finishes the discussion of waveguides by introducing some more exotic types of waveguides and discussing their applications and drawbacks. Topics include the double-ridge metal waveguide that extends bandwidth, cylindrical waveguides, waveguides for very high power, integrated optical waveguides, and photonic crystal waveguides
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[@hishigherness8472]

I appreciate the waveguidance...lol

[@empossible1577]

Any time! 😀

[@tominku]

When and where those high order modes are used in practice?

[@empossible1577]

They are usually not used and waveguides are most often designed to support only a single mode. That is because the different modes propagate at different speeds and this distorts signals. However, that is not what you asked.
There are multimode optical fibers that support hundreds or thousands of modes. It is not so much that the higher order modes have a specific purpose. It is more that it becomes much easier to get light into and out of them. Single mode optical fibers require much more precise alignment.
Some people are researching using each mode as a different information channel, effectively extending the bandwidth of a waveguide. The real challenge here is that any imperfection or discontinuity in the waveguide tends to scramble power between the modes, causing cross-channel interference.
The fifth (or sixth?) mode of a cylindrical metal waveguide has an azimuthal polarization that propagates with minimal loss. This is used for very high power waveguides and is called and “over moded waveguide.”
There are some sensors that make use of coupling between the various modes in a waveguide. Look up “turn around point long period gratings” for one interesting example of this.
I am sure there are other applications for the higher order modes that I am not thinking about.
Hope this helps!