Saturation Fluence
For pulsed operation, in the limiting case of short pulses, absorption can be expressed through the fluence
where time should be small compared to the relaxation time of the medium; it is assumed that the intensity is zero at . Then, the saturable absorption can be written as follows:
where saturation fluence is constant.
In the intermediate case (neither cw, nor short pulse operation), the rate equations for excitation and relaxation in the optical medium must be considered together.
Saturation fluence is one of the factors that determine threshold in the gain media and limits the storage of energy in a pulsed disk laser.
Read more about this topic: Saturable Absorption
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