Quantum Dot Lasing

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Background: This invention relates to nanoparticle lasing complexes that comprise a room temperature solution comprising quantum dots that each have an average diameter between 3 and 6 nanometers. All quantum dots in the solution are substantially the same size, and each quantum dot is capped with a capping material that passivates and protects the surface, maximizes the emission yield, reduces the line width of the emission from the quantum dot, and acts to suspend the quantum dot in the solution. The solution may preferably comprise toluene or water. The capping material may comprise a wide bandgap semiconductor material such as zinc sulfide, or an organic molecule such as tri-n-octylphosphine oxide (TOPO). Also disclosed herein is an exemplary laser apparatus comprising cadmium sulfide (CdS) quantum dots in a 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/cm.sup.2. The relative lower gain threshold compared to that of CdS 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.