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Derive the expression for the round trip gain G of a simple laser cavity. You may assume that the laser medium fills the cavity completely and you may use the expression I=I0 e(k-ˠ)L where I is the irradiance , L the length of the cavity and (k-ˠ) the effective gain coefficient.

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Calculate how thick an absorber needs to be absorb 75%of the incoming light using the lambert-beer law for absorption. How is the small gain coefficient k of a laser defined in relation to the absorption coefficient α