Spatially resolving spectrometer for characterisation of broad-area laser diodes

The mode pattern of the BALD (Broad-Area Laser Diode) is characterized and measured using a 1-GHz resolution double-pass spectrometer. The design of spectrometer allowed also a spatial discrimination with 1mum resolution. The construction and design of the double-pass grating is analyzed and discussed. A matrix approach is developed for the double-pass measurement arrangement. The developed procedure of analysis of spatially resolved spectra provides unique information about broad-area laser diode active medium and cavity geometry and potentially will help to predict the reliability of the laser diode. The developed model is based on paraxial approximation.;The laser diode modes are measured in the near-field & far-field. Measurements of spatially & spectrally resolved spectra of the laser radiation as a function of pumping current and observed polarization are conducted for laser diodes of different geometries.;Obtained data suggests that a careful choice between the length and width of BA laser diode cavity will help to avoid the coherence kink phenomenon and, therefore, will significantly improve the overall reliability of BALDs.