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 1mkm 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.