Dynamics of laser intracavity absorption

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Abstract
The dynamical behavior of a multimode dye laser with an intracavity absorber has been investigated theoretically as well as experimentally. This behavior is described by a system of rate equations which has to include the influence of saturation in the case of large absorption coefficients. With the rate-equation-system model calculations have been performed for the cases of saturated and unsaturated intracavity absorption. Saturation of the absorption is shown to severely reduce the sensitivity of intracavity absorption. In general, the sensitivity is governed by the average lifetime of the individual modes. This mode lifetime is limited by large intensity fluctuations which are capable of quenching individual modes. The probability for mode quenching is shown to increase with increasing spectral power density. For this reason, intracavity absorption gains sensitivity close to the lasing threshold. The theoretical results are found to be in excellent agreement with our measurements. In addition, discrepancies in previous work have been resolved within the framework of our theory. With the detailed understanding of the intracavity absorption, reliable measurements of very small, absolute absorption coefficients have become possible.