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Optical Engineering - Lasers

  1. Nov 21, 2013 #1
    1. The problem statement, all variables and given/known data

    Consider an amplifying medium, composed of homogeneous broadening four-level atoms as show in figure 26.5, page 557 of textbook.

    http://img689.imageshack.us/img689/6108/lt2f.png [Broken]

    Amplification is to occur on the 2-to-1 transition. The medium is pumped by a laser of intensity [itex]I_{p}[/itex], which is resonant with the 3-to-0 transition. The spontaneous decay processes are indicated on the diagram. The total number of gain atoms is [itex]N_{T} = N_{0} + N_{1} + N_{2} + N_{3}[/itex]. The various parameters are:

    [itex]k_{32} = \frac{10^{8}}{s}; k_{21} = \frac{10^{3}}{s}; k_{10} = \frac{10^{8}}{s}; k_{30} = k_{31} = k_{20} = 0[/itex]
    [itex]σ_{p} = 4x10^{-19} cm^{2}; σ = 2.5x10^{-18} cm^{2}; λ_{30} = 300 nm; λ_{21} = 600 nm; N_{τ} = 2.0x10^{26} m^{-3}[/itex]

    Assuming an ideal four-level laser system determine:

    a) The pump irradiance required to sustain a small signal gain coefficient of [itex]\frac{0.01}{cm}[/itex]
    b) The saturation innradiance.
    2. Relevant equations



    3. The attempt at a solution
    I know that [itex]γ_{0} = σR_{p2}τ_{2}[/itex]

    I know that [itex]τ_{2} = \frac{1}{k_{2}}[/itex]. I'm just not exactly sure what [itex]R_{p2}[/itex] is and how to find it.

    Thanks for any help.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
    Last edited by a moderator: May 6, 2017
  2. jcsd
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