“…Since the CdSe QDs were first demonstrated to be available in the visible optical amplification (Klimov et al, 2000), nowadays, the wavelength of optical amplification have explored from visible to infrared. For infrared broadband PL semiconductor QDs, the research system is mainly about PbS, InAs, PbSe, HgTe, and so forth (Steiner et al, 2004;O'Connor et al, 2005;Sukhovatkin et al, 2005). Among them, PbS QDs with a large Bohr exciton radii (~18 µm) and a moderate band gap at near/mid-infrared Comparison of normalized emission spectra produced using low (blue) and high (red) pump intensities (inset), which are dominated by spontaneous PL and ASE, respectively, shows the ASE as a spectrally narrowed, red-shifted band (Schaller et al, 2003).…”