Noise transformation and induction of spatial structures and instabilities by laser beams in nonlinear systems with distributed feedback

Two problems involving the propagation of laser radiation in a distributed-feedback system are discussed. One involves the transformation of noise and a determination of the conditions under which quantum nondemolition measurements are possible. The second problem concerns an experiment on the induction by light of hydrodynamic instabilities (of the Rayleigh–Bénard convection type) in an anisotropic liquid (the treatment is classical). The discussion stresses the possibility of observing these states, which are of fundamental importance to physics, in the field of stable cw lasers with high coherence properties. This group of problems is related to one of the scientific interests of professor S. A. Akhmanov in the later years of his life. The present study, carried out under the strong influence of his ideas, is devoted to his memory.