![]() ![]() Here we demonstrate a practical approach for obtaining optical gain in the single-exciton regime that eliminates the problem of Auger decay. A complication associated with this multiexcitonic nature of light amplification is fast optical-gain decay induced by non-radiative Auger recombination, a process in which one exciton recombines by transferring its energy to another. Because of an almost exact balance between absorption and stimulated emission in nanoparticles excited with single electron-hole pairs (excitons), optical gain can only occur in nanocrystals that contain at least two excitons. However, nanocrystals are difficult to use in optical amplification and lasing. They show photoluminescence with high quantum yields, and their emission colours depend on the nanocrystal size-owing to the quantum-confinement effect-and are therefore tunable. Lett.Abstract : Nanocrystal quantum dots have favourable light-emitting properties. Multiparticle interactions and stimulated emission in chemically synthesized quantum dots. Femtosecond high-sensitivity, chirp-free transient absorption spectroscopy using kilohertz lasers. Tunable near-infrared optical gain and amplified spontaneous emission using PbSe nanocrystals. Confined excitons, trions, and biexcitons in semiconductor microcrystals. One-pot synthesis of high-quality zinc-blende CdS nanocrystals. ![]() Effect of quantum and dielectric confinement on the exciton-exciton interaction energy in type-II core/shell semiconductor nanocrystals. Multiexcitons confined within a subexcitonic volume: Spectroscopic and dynamical signatures of neutral and charged biexcitons in ultrasmall semiconductor nanocrystals. Confinement-enhanced biexciton binding energy in semiconductor quantum dots. Optical nonlinearities and ultrafast carrier dynamics in semiconductor nanocrystals. Measurement of the size-dependent hole spectrum in CdSe quantum dots. Absorption cross sections and Auger recombination lifetimes in inverted core/shell nanocrystals: Implications for lasing performance. Light amplification using inverted core/shell nanocrystals: Towards lasing in the single-exciton regime. Zero- to one-dimensional transition and Auger recombination in semiconductor quantum rods. Lasing from semiconductor quantum rods in a cylindrical microcavity. Quantization of multiparticle Auger rates in semiconductor quantum dots. Optical gain and stimulated emission in nanocrystal quantum dots. From amplified spontaneous emission to microring lasing using nanocrystal quantum dot solids. Color-selective semiconductor nanocrystal laser. Synthesis and characterization of nearly monodisperse CdE (E = S, Se, Te) semiconductor nanocrystallites. (ed.) Semiconductor and Metal Nanocrystals: Synthesis and Electronic and Optical Properties (Marcel Dekker, New York, 2003) Semiconductor clusters, nanocrystals, and quantum dots. This effect breaks the exact balance between absorption and stimulated emission, and allows us to demonstrate optical amplification due to single excitons.Īlivisatos, A. The resulting imbalance between negative and positive charges produces a strong local electric field, which induces a giant ( ∼100 meV or greater) transient Stark shift of the absorption spectrum with respect to the luminescence line of singly excited nanocrystals. Specifically, we develop core/shell hetero-nanocrystals engineered in such a way as to spatially separate electrons and holes between the core and the shell (type-II heterostructures). ![]() Because of an almost exact balance between absorption and stimulated emission in nanoparticles excited with single electron–hole pairs (excitons), optical gain can only occur in nanocrystals that contain at least two excitons. Nanocrystal quantum dots have favourable light-emitting properties. ![]()
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