  Subpicosecond wavelength non-degenerate differential transmission (DT) was
used to observe the carrier relaxation mechanism in GaN based quantum well (QW)
with and without metal nanoparticles (MNPs) in it. The spontaneous emission
dominates the stimulated emission for above the GaN band edge excitation
energy. We observed long decay times for Au-embedded sample and short decay
times for Ag-embedded sample with respect to reference sample.
