Facet temperature distribution of a room temperature continuous-wave operating quantum cascade laser

The facet temperature distribution of a room temperature continuous-wave (CW) operating quantum cascade laser was experimentally measured based on the micro-Raman intensity ratio analysis of the Stokes and anti-Stokes phonon lines. A 'W'-shaped temperature distribution was observed in the active region. We found that the traditional thermal simulation using the Fourier law is not sufficient in explaining our experimental results and other simulation models need to be explored. The active region temperatures at different CW operating currents were also measured. Our work is useful for device failure analysis and optimization of thermal management.