The pioneering research of coherent brightening of a resonantly absorbing medium known also as electromagnetically induced transparency (EIT), as well as of lasing without inversion (LWI) accomplished in IAP RAS promoted development of a prominent, rapidly advancing trend in coherent optics that unifies interference phenomena in multilevel quantum ensembles.

The theoretical results obtained in IAP RAS were decisive in promoting this direction of research worldwide. In particular, physical mechanisms of EIT and LWI were studied; an acoustic method of inducing optical transparency was proposed; a method allowing one to take into account the influence of coherent radiation on atomic relaxation was elaborated; foundations for laser Mossbauer spectroscopy of nuclear gamma transitions were laid down. Using results of these researches pioneering inversion-free lasers were created and a number of new effects were discovered. Realization of EIT in solids (creation of nonlinear optical elements of new generation, cells of optical memory) is regarded to be especially promising. LWI is expected to facilitate creation of the first gamma-laser.