Laser media based on polymethine dyes

An account is given of the results of investigations of the use of polymethine (cyanine) dyes as passive Q switches and active media for lasers operating in the visible and nearinfrared range. Characteristic features of the electronic structure of cyanines, which govern their switching and lasing properties, are considered. An analysis is made of the relationship of these properties with isomerisation processes, as well as with vibronic and intermolecular interactions in solutions of polymethine dyes. The spectral, luminescence, and nonlinear optical characteristics of polymer laser media based on polymethine dyes are considered as a function of their structure and the nature of the matrix containing them. Different approaches to the modification of the molecular structure of cyanines, with the aim of achieving efficient lasing characterised by a large 'red' shift, are discussed. Criteria for the selection of the optimal polymethine dyes and solvents are formulated, including the choice of polymer matrices, for when these dyes are used in passive switches and active media of lasers.