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Plasma frequency, shield, laser

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  1. Nov 28, 2013 #1
    1. The problem statement, all variables and given/known data
    A plasma is to be used as a shield against a laser in the visible spectrum (400 - 700 nm wavelength light) by attenuating the field amplitudes.

    (a) What is the minimum electron density that should be used?
    (b) What thickness of this shield would be needed to reduce the power of a 10 kW beam with wavelength 500 nm to below 1 W?


    2. Relevant equations
    omega p = √(Ne *e^2)/(me*epsilon0)

    Ne= electron density
    e= electron charge
    me= electron mass
    omega p = plasma frequencey

    V= Fλ

    V= velocity/speed of light
    F= frequency
    λ= wavelength



    3. The attempt at a solution

    For part a, is this the way to go about it?

    F=v/λ = 3x10^8 / 700nm = 4.29x10^14

    Ne= (omega p)^2 *me*epsilon0 / e^2 = 5.78 x10^-25

    (b)
    Pretty stuck on what equations to use here

    any help much appreciated, thanks
     
  2. jcsd
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