In this letter, the random laser is fabricated by an active waveguide structure constructed by covering the layer of poly methyl methacrylate (PMMA) doped CdSe/ZnS colloidal quantum dots (CQDs) onto the Ag nanoisland structures. There is a low threshold due to the excellent overlap of the plasmonic resonance of the Ag nanoislands with the photoluminescence spectrum of the CQDs and the strong confinement mechanism provided by the active waveguide layer. The performances of random laser can be tuned through the flexible fabrication of Ag nanoisland structures. The spectral evolution shows a stability of random lasing under uninterrupted laser irradiation owing to the super chemical and photo stability of CdSe/ZnS CQDs and the stable external environment for CdSe/ZnS CQDs provided by the PMMA matrix.National Natural Science Foundation of China Grant n. 11174160, Grant n. 11474052 and Grant n. 11274062. Jiangsu Overseas Visiting Scholar Program for University Prominent Young & Middle-Aged Teachers and Presidents under N. 2018001
