Exothermal spectral diffusion in media with large diagonal disorder of 4f-states: the role of phenomenology models in cooperative and coherent optical phenomena

摘要

Abstract: In an ensemble of rare earth ions (REI) with large energy disorder, interaction of the ions between themselves and with vibrations of the media gives rise to spectral diffusion, ie., to energy redistribution within the subsystem of the ensemble's excited states. It usually occurs at concentrations $GREQ 10$+19$/ cm$+$MIN@3$/. At low temperatures kT $VLS W (W is the disorder scale), the process turns into energetically unidirectional exothermal spectral diffusion (ExoTSD). Below we consider general regulations of the ExoTSD, its effect on formation of cooperative, coherent, and critical photoresponse of the system. Special attention is paid to the role of collective 4f-states in media with high REI concentration. !8