Saturated absorption resonances in an active interferometer

Saturated absorption resonances are widely used in spiectroscopy and for laser frequency stabilization. To obtain such resonances, the absorber can be placed both inside the laser cavity and outside it, In this work, a promising way of obtaining saturated absorption resonances is presented. It is based an the use of an active interferometer of the Fabry-Perot type, in which an amplifying medium is placed in addition to an absorbing cell. Our theoretical and experimental investigations shown that the such system makes it posible to obtain an advantage in Signal-to-Noise ratio in comparison with a widely used passive interferometer. An original system of two weakly coupled optical cavities considered as well. One of the cavities contains an amplifying medium and another one contains an amplifying and absorbing media. Such a system is an improved active imerferometer and our estimations show that it make it posible to increase the intensity of optical resonances and hence the signal-to-noise ratio.