High-resolution spectroscopy of weakly absorbing objects based on a competing beam method

A new competing beam method is proposed for intracavity measurement of weak absorption. In this method two independent lasers with the same active medium are employed. An investigated sample is placed inside the resonator of one of the lasers with a narrow tunable emission line. In contrast to the selective intracavity absorption method, photoelectric recording of the spectra can be used in the proposed method and this can be done for narrow lines as well as for wide absorption bands. Moreover, the new method can be used to determine the two-photon absorption spectra.