Lasers based on Gain media with a large gain bandwidth, caused by a strong interaction of electronic transitions with phonons.

In some Laser gain media, particularly in those doped with transition metal ions, there is a strong interaction of the electronic states with lattice vibrations, i.e., with phonons. This vibrational-electronic interaction leads to a strong Homogeneous Broadening and thus to a large gain bandwidth. In the early years of laser technology, vibronic lasers were sometimes called phonon-terminated lasers.