Competition between modes generated due to adjacent transitions

An analysis is made of competition between modes emitted due to adjacent transitions having a common upper level. Conditions are obtained for the onset of lasing due to one transition in the presence of lasing of arbitrary intensity due to the other transition in standing- and traveling-wave lasers. Both transitions were assumed to be homogeneously broadened. Allowance is made for level degeneracy, collisional broadening of the dipole-forbidden transition between the lower active levels, and collisions with the buffer gas that equalize the populations of the lower active levels. The ranges of single-mode and two-mode lasing are determined as a function of the radiation intensity, the spectroscopic parameters of the transitions, and their collisional broadening.