Finestructure in the spectra of GaAlAs heterostructure lasers

An experimental setup allowing high resolution measurements to be performed on the emission lines of injection lasers is described. Axial and transverse mode laser structures can be observed as they change under dc input current variations and modulation signal influence. A resolution limit of 80 MHz is obtained. Results show a new finestructure ripple on the emission lines of GaAlAs heterostructure lasers which is distinct from the transverse mode structure. Axial mode amplitude limiting and simultaneous spectral widening are observed with increasing laser drive currents.