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Homework Help: Laser:population rate equation

  1. Apr 25, 2007 #1
    1. The problem statement, all variables and given/known data
    Simultaneous Laser Emission on Two Lines
    Consider the multi-level system show in the figure where amplification can occur at frequencies [tex]\omega_{12}[/tex] and [tex]\omega_{21}[/tex]. The arrow "triplets" are meant to indicate the 3 Einstein absorption and emission processes that take place between levels 2 and 3. Write down the population rate equations for levels 1, 2 and 3.

    The figure is attached.

    My problem is: I don't know if I have to introduce the pumping power inside the population rate equations.

    2. Relevant equations
    Ni=number of particles in level i
    Between levels 1 and 2 we have:
    [tex]\downarrow \uparrow \downarrow[/tex]
    first down arrow: spontaneous trasition rate
    up arrow: absorption rate
    second down arrow: stimulated emission rate

    3. The attempt at a solution
    For level 3 I have:
    [tex]dN_{3}/dt = - N_{3}A_{31} + N_{1}B_{13}W(\omega_{13}) - N_{3}B_{31}W(\omega_{13})[/tex]

    Level 2:
    [tex]dN_{2}/dt= - N_{2}A_{21} + N_{1}B_{12}W(\omega_{12}) - N_{2}B_{21}W(\omega_{12})[/tex]

    Level 1:
    [tex]dN_{1}/dt = - dN_{3}/dt - dN_{2}/dt - N_{1}R{1}[/tex]

    Should I add P3 to level 3 and P2 to level 2?

    Attached Files:

    Last edited: Apr 25, 2007
  2. jcsd
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