Side-Mode Excitation in Single-Mode Laser Diodes

A double-peaked spectrum in some distributed feedback laser diodes is demonstrated to relate to axially confined catastrophic optical damage (COD), followed by the excitation of a transversal optical mode. The melting-regrowth kinetics of CODs also reveal another possibility of COD-induced side optical modes in a fiber distributed Bragg reflector pump laser diode. A third case completely reverses the cause-effect relationship between CODs and lateral optical harmonics.