Laser에서의 協同效果와 非平衡相變化 = COOPERATIVE EFFECTS AND NONEQUILIBRIUN PHASE TRANSITION IN LASER

다국어 초록 (Multilingual Abstract)

Laser is a system far away thermal equilibrium. But it has been suggested that the statistical properties of the laser light at threshold have close analogy to the thermodynamic phase transition of equilibrium system. We study the nonequilibrium phase transition of laser light by utilizing the analogy. The Ginzburg-Landau model for the second-order phase transition in ferromagnetic system is introduced and solved by Gaussian approximtion. The order parameter for the laser light is the amplitude of the electric field and the atomic population inversion is a quantity corresponding to the thermodynamic temperature. The quantities associated with the critical indices are discussed together with the fluctuations in the threshold region.
The laser light above threshold show a high degree of coherence. The cooperative effects and self-organization producing such a coherent state are discussed in terms of statistical entropy. The description using the entropy is carried out by applying the results of the stochastic theory used for the nonlinear chemical reaction.