Gain clamping

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Gain clamping (engl., Dt. Gain limit ) is a term from the quantum optics . He describes the phenomenon that (also called cw operation) in the steady operation of the laser gain (dt. Gain ) of the laser medium exactly the threshold for laser oscillation corresponds. At this threshold value, the amplification of the light field corresponds exactly to the resonator losses, which are primarily determined by the resonator mirror. Further, often negligible, loss mechanisms are scattering of the light field within the resonator and absorption by the laser medium. Once stationary laser operation has been achieved, even a considerable increase in the pump power would not further increase the gain. At the threshold value of the laser amplification, the intensity of the light field within the laser resonator is constant, since amplification and losses cancel each other out.

Gain clamping is caused by gain saturation (engl., Dt. Gain saturation ) and can be intuitively understood as follows: If we could by increased pumping power the gain above the threshold increase, the gain would exceed the value of the resonator losses. This would lead to an exponential increase in the laser intensity within the resonator. However, due to the increased intensity, the gain saturation effect in turn leads to a decrease in the gain back to the threshold value.

The mechanism just described can lead to relaxation oscillations in laser operation .

Individual evidence

1. ^ PW Milonni, JH Eberly: Lasers (= Wiley Series in Pure and Applied Optics . Volume 7) John Wiley & Sons, 1988, ISBN 0-471-62731-3 , p. 321.