Highly Efficient Amplified Stimulated Emission from CdSe-CdS-ZnS Quantum Dot Doped Waveguides with Two-Photon Infrared Optical Pumping

In principle, a population inversion in semiconductor quantum dots can be achieved through electrical, chemical or optical pumping. To date however, it has only been successfully demonstrated with optical pumping in the 1-photon absorption range (i.e., above the semiconductor bandgap). Under these conditions amplified stimulated emission (ASE) in 1-D waveguides and lasing within microsphere cavities and distributed feedback structures has been observed. In these studies, it was demonstrated that for the archetypal CdSe system, a given nanocrystal must encompass more than one electronhole (e–h) pair for a population inversion to be achieved. This value reflects the twofold degeneracy of the lowest electronic state in the wurtzite crystal structure.