q1
Posted: Tue May 17, 2022 8:15 pm
q1
A laser medium produces monochromatic light as a consequence of transitions between two specific energy levels, E2 and El. (a) Show how the rates at which the populations of the two separate energy levels change can be written in terms of the Einstein coefficients (you should define all of the parameters you use). (b) Derive an expression for the rate of change of photon density inside the laser cavity (i.e. in terms of the population of the two energy levels, the photon density in the cavity and the Einstein coefficient related to stimulated emission). (c) Given that the time constant for spontaneous emission for a material inside the laser cavity is 1 x 10-7s, and that the frequency of the transition is 4.74 x 1014 Hz, determine the rates of stimulated and spontaneous emission at temperatures of 300 K and 400 K.
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