In fabricating a semiconductor laser producing light with a wavelength of
770 to 810 nm, impurities are introduced into an MQW active layer near a
light emitting facet of the laser to form a disordered region
constituting a window layer. Pump light is applied to the window layer to
generate photoluminescence whose wavelength .lamda. dpl (nm) is measured.
A blue shift amount .lamda. bl (nm) is defined as the difference between
the wavelength .lamda. apl (nm) 0f photoluminescence generated by
application of pump light to the active layer on the one hand, and the
wavelength .lamda. dpl (nm) of photoluminescence from the window layer
under pump light irradiation on the other hand. The blue shift amount
.lamda. bl is referenced during the fabrication process in order to
predict catastrophic optical damage levels of semiconductor lasers.