1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Dielectrics scattering electromagnetic waves

  1. Jan 11, 2008 #1
    Hello everyone,
    First and foremost I would like to see if everyone's having a good day? (assuming you respond yes) Awsome! Secondly I was hoping someone would be able to help me understand how dielectrics work.

    I don't need to know everything about dielectrics. I only need to know how they affect electromagnetic waves passing through them. More specifically how they would affect the amplitude of an RF signal having a frequency of anywhere between 10 MHz to 100 GHz and an unmodulated amplitude.

    The reason I would like to know specifically about dielectrics is because I read the following from a patent description which can be found here http://www.freepatentsonline.com/5230029.html" [Broken] :

    "The results of non-normal plane-wave scattering from a planar three-layer guiding structure as illustrated in FIG. 1 in which the central dielectric film or layer is active are described." "A fine-grained scan of the plane-wave incidence angle, has revealed the existence of narrow discrete angles where large amplitude scattering resonance is obtained. Enhancements in the scattered field intensities on the order of 100 have been observed using active films 80 as thin as 6 microns."

    From what I understand this means that this dielectric film 80 reflects an electromagnetic wave which scatters the amplitude of the incedent wave.

    Ofcourse I could be terribly wrong seeing as how this is all very confusing to me, So if anyone out there knows what's really going, could you please either tell me "no, you're not right" or instead tell me "yes, you're correct" and then explain how the dielectric does this.

    Sorry if this was all very confusing, but any help would be most appreciated.
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Jan 11, 2008 #2


    User Avatar

    ugh... I'd forgotten how much I don't like patents: they usually take for ever to say nothing.

    Anyway... I don't really get your question, but it seems that the device is nothing more than an active flat cavity. The two outer layers act as cavity mirrors and the central dielectric is the gain medium. The resonance is tuned by angle. I would suggest you read the wikipedia entry on lasers and perhaps thin film interference.
  4. Jan 14, 2008 #3

    Claude Bile

    User Avatar
    Science Advisor

    The properties of the devices/structures the patent depend primarily on the dimensions of the waveguide structure, not so much the dielectric itself.

    What the patent authors are doing are making waveguides with what are called leaky modes. These modes are slightly different to guided modes in that they decay slightly with length (hence the name), but still have a well defined field shape (as opposed to radiation modes). Importantly, leaky modes, have well defined propagation constants, which means that the energy that leaks out of these modes at well defined angles.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook