Figure 2

(a) Excitation density dependence of the PL spectra of NC1 sample under 3 ns laser pumping. The appearance of the ASE band above about 0.75 mJcm−2 is evident. (b) Excitation density dependence of the PL spectra of NC1HMDS sample under 3 ns laser pumping. The appearance of the ASE band above about 0.6 mJcm−2 is evident.