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Electromagnetic waves in a cavity resonator

  1. Aug 18, 2011 #1
    If EM waves are pumped into a resonant cavity at it's resonant frequency will each incoming wave add it's energy to amplify the wave(s) in the cavity?

    I know that if you pulse a light source into a circular wave guide and you pulse the light source each time the light wave returns to it's starting point the waves amplitude will increase with each pulse inputted....

    Is the same true for resonant cavities?
  2. jcsd
  3. Mar 16, 2015 #2
    If the initial pulse is followed by subsequent pulses that are in phase with the returned pulses you will make up for the propagation losses in the cavity. You can also use a sub-harmonic of the resonant frequency of the cavity to keep the amplitude strong and use the cavity as a frequency doubler or tripler.
  4. Mar 16, 2015 #3


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    Each wave applied will increase the amplitude inside the resonator, which acts as a store. When the amplitude inside grows until it equals that outside, we have near equilibrium, but a small flow of energy will take place into the resonator to make up for energy losses. When you stop applying waves from outside, the resonator will gradually supply its stored energy to the outside world in the same way.
  5. Mar 17, 2015 #4
    The cavity or any other tank circuit acts like a bell. One tap and it rings and the amplitude decays to nothing. If you tap in phase with the oscillation it will be sustained. Is that what you mean?
    Last edited: Mar 17, 2015
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