Polarization photon echo spectroscopy

A review of theoretical and experimental works on the polarization photon-echo spectroscopy (PPE spectroscopy) is carded out. The main attention is payed to the following advantages of the PPE spectroscopy. First, the PPE spectroscopy, free of the influence of the inhomogeneous spectral line broadening, allows to make the high precision measurements within the envelope of a inhomogeneously broadened spectral line. Second, the high resolution ability of the PPE spectroscopy, directly in the temporal field, unables to accomplish the investigations of the fast relaxation processes, when ultrashort nano- and picosecond exciting pulse are used. Third, in the PPE spectroscopy the investigated relaxation processes are not subjected to the perturbing action of the intensive laser radiation. Farther, it is necessary to note the flexibility of the PPE spectroscopy consisting in the existence of a great number of various methods used for receiving different spectroscopic information. Finally, as far as the signal intensifies of the photon echo and of its variants are proportional to the squared number of the resonant atoms (molecules), it secures the definite advantages for the PPE spectroscopy as compared to the spectroscopk methods based on the non-coherent phenomena (especially for low pressure a gas considered). The possibilities of new experiments on photon echo and its variants aimed for obtaining a detailed new spectroscopic information are discussed.