Stimulated Emission of Active Media in the Red Spectral Range

Spectral, luminescent, and lasing characteristics of chromene dyes and their julolidine analogs emitting in the red spectral range are investigated experimentally and theoretically. It is shown that the cause for a low lasing efficiency of oxochromene compared with iminochromene is a high intersystem crossing to the T 1 state and the presence of the induced T 1→T n absorption in the region of the luminescence band.