The pioneering experiments by Hunbery-Brown and Twiss had demonstrated that spatio-temporal field correlations can provide important information about physical objects in nature and laboratory, sometimes not available in other approaches. In optical domain the spatio-temporal photon correlations are observed at frequencies, which are by many orders of magnitude lower as compared to optical frequency. This results from the evident fact that in correlation measurements one observes the low-frequency beatings in space-time between the high-frequency light fields. The spectroscopy of intensity fluctuations in atomic non-linear optics was intensively investigated by our group .
After invention of lasers, which are considered to be a source of bright coherent light with the low noise level, the problem of natural fluctuations in laser radiation attracted a lot of attention. An important contribution was made by our group, when we suggested the sub-Poissonian laser with regular excitation of working medium . The sub-Poissonian laser is the source of non-classical light field with suppressed photon (shot) noise. The semiconductor sub-Poissonian laser was later realized experimentally by Japanese, US, European and Russian groups.
The first demonstrations in mid 80'th of non-classical states of bright coherent light (sub-Poissonian, squeezed etc.) with suppressed quantum fluctuations stimulated active experimental and theoretical research. Our work in this direction aimed at, on the one hand, on the search of effective methods of generation of non-classical light, and, on the other hand, on the possible applications of non-classical states of light for optical measurements with sensitivity far beyond the standard photon noise limits. It is worth to mention here the works of our group on the non-classical signal exchange between active optical cavities, on the super-radiant laser, on the modern vertical-cavity-emitting-semiconductor laser (VECSEL) etc.
The first observations of non-classical squeezed light were done with the light wave fronts of simplest spatial structure: the spatially single mode light. In order to exploit the rich possibilities, provided by optics for light manipulation in space (diffraction, interference, Fourier processing etc.), we suggested  the concept of photon-noise-free light wave fronts, based on the spatially-multimode squeezing. This stimulated the rise of quantum imaging, the growing area of experimental and theoretical research in quantum optics.
Now activity of our group is extended to the developing field of quantum information. The idea to introduce optical parallelism for non-classical light, coming from quantum imaging, into the protocols of quantum information, such as quantum teleportation, super dense coding, quantum computation and others, is stimulating our current research.