A high-resolution spectroscopic technique for the analysis of the external quantum efficiency of a multimode semiconductor laser

The high-resolution emission spectra of a GaN-based semiconductor laser were utilized to investigate the external differential quantum efficiency variation with temperature and stability over an extended period of continuous operation time. Moreover, the dynamics and evolution of the optical gain and longitudinal modes emitted both below and above threshold current were also reported. Upon studying the L-I curves over the full range of operating current and temperature, three distinct temperature regimes of the quantum efficiency were identified, with the regime of the temperature range 285–301 K yielding the highest stability. The thermal stability of the laser was also assessed by monitoring the variation of threshold current with temperature.