Coupled transverse modes in three-level cascade lasers

The formation and dynamics of patterns in three-level cascade lasers is ana lyzed in the case of a laser cavity bounded by curved mirrors. It is found that the gaussian mode from the upper transition turns on gaussian emission from the lower one. Once the two fields are emitting in a TEM00 mode, the former one undergoes mode switching towards a non-resonant doughnut mode, d ue probably to an AC Stark splitting of the intermediate energy level of th e system. Al high pump rates, coupled dynamical states appear. (C) 1999 Els evier Science Ltd. All rights reserved.