Lecture -- Other Waveguides

Ғылым және технология

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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Пікірлер: 8

  • @HisHigherness8472
    @HisHigherness84722 ай бұрын

    I appreciate the waveguidance...lol

  • @empossible1577

    @empossible1577

    2 ай бұрын

    Any time! 😀

  • @tominku
    @tominku2 ай бұрын

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

  • @empossible1577

    @empossible1577

    2 ай бұрын

    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!

  • @localfuture1484
    @localfuture1484Ай бұрын

    Hi, I cannot figure out why "only tangential components at the surface of the metal would do help for High Power". Could you further explain it?

  • @empossible1577

    @empossible1577

    Ай бұрын

    Tangential components are forced to be zero due to boundary conditions. Since they are zero, they cannot induce surface currents that would produce loss. If the mode at normal components, those do not have to be zero and will induce surface currents, leading to much lossier modes. Does this help?

  • @localfuture1484

    @localfuture1484

    Ай бұрын

    @@empossible1577 Hi, Still some confusions. Q.1 It seems like "boundary conditions" you mentioned are applicable for Electrostatic. Can those "boundary conditions" still hold for "WaveGuides" case here? I think it's not static for "WaveGuide" case. Q.2 "Tangential components are forced to be zero". I think the precodition is that This is Perfect Electric Conductors. Thus, in PEC, the normal component within conductor is still Zero (only normal component within "Dielectric" exists. Can this cause loss?). Q.3 For energy loss, where does the energy go? Go to Dielectric or Metal?

  • @empossible1577

    @empossible1577

    Ай бұрын

    @@localfuture1484 Q1 - In this course I derive the BCs for electrostatics. It turns out it is the same boundary conditions for electrodynamics. It is very good you caught this and was curious! Q2 - Yes, I am assuming PEC. There is no loss for PEC. Despite this, the normal component in the dielectric, but right against the metal, can be very non-zero. Q3 - When there is loss, you cannot assume PEC. In this case there will be an electric field, particularly the normal component. This induces currents which leads to ohmic loss. While there is no perfect dielectric and there will always be loss, the vast majority of energy is absorbed by the metal. This gets converted to heat. Hope this helps!!

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