Intracavity laser spectroscopy with nonlinear frequency conversion

A new absorption spectroscopy method is proposed. This method is based on intracavity generation of sum and difference frequencies and it is analogous, in respect of its physics and capabilities, to intracavity laser spectroscopy. An investigation is reported of the dependence of the sensitivity of the new method on the efficiency of nonlinear frequency conversion and on the phase relationships obeyed by waves interacting in a nonlinear crystal. It is reported that the sensitivity of the new method in determination of weak absorption is between two and three orders of magnitude higher than the extracavity variant.