US Patent 7778301 Cadmium sulfide quantum dot lasing in room temperature liquid solution

Disclosed is a lasing complex comprising a room temperature solution containing cadmium sulfide (CdS) quantum dots. Optical gain has been observed in CdS nanocrystal quantum dots in strong confinement regime in toluene solution at room temperature using femtosecond transient absorption techniques. The optical gain lifetime is measured to be 20 picoseconds under pump fluence of 0.77 mJ/cm2. The relative lower gain threshold compared to that of CdSe quantum dots is attributed to the long lifetime of fluorescence and biexcitons and the relatively sharp photoluminescence linewidth. The CdS nanocrystals are excellent gain media for semiconductor quantum dot based blue lasers.