Topic
Spontaneous emission
About: Spontaneous emission is a research topic. Over the lifetime, 12855 publications have been published within this topic receiving 323684 citations.
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TL;DR: The chemical process used to terminate the surfaces of the silicon quantum dots changes the internal electronic structure and thus plays an important role in the resultant emission wavelength and radiative lifetime, and ultimately determines the solubility.
Abstract: For silicon quantum dots to be used in biomedical applications it is essential that they have a substantial photoluminescence quantum yield in the visible region, have a fast radiative recombination rate, and are water soluble and hydrophilic to prevent aggregation and precipitation in a biological environment. The chemical process used to terminate the surfaces of the silicon quantum dots changes the internal electronic structure and thus plays an important role in the resultant emission wavelength and radiative lifetime, and ultimately determines the solubility. [18] Silicon quantum dots with an oxide surface passivation typically display a dipole-forbidden yellow-red emission with radiative lifetimes of 10 3 –10 6 s. [18, 26] This slow rate of recombination limits the use of oxide-passivated silicon quantum dots in biological imaging. However, silicon quantum dots with a hydrogen or carbon surface passivation have electric-dipole-allowed direct band gap transitions that lead to blue photoluminescence with fast recombination rates of 10 8 –10 9 s. [18, 20]
515 citations
TL;DR: Amplified spontaneous emission and stimulated emission spectra of the GaAs/AlGaAs quantum wires exhibit fine structure arising from transitions between lateral, one-dimensional electron and hole subbands.
Abstract: We report the first observation of stimulated emission in quasi-one-dimensional semiconductor quantum wires Amplified spontaneous emission and stimulated emission spectra of the GaAs/AlGaAs quantum wires exhibit fine structure arising from transitions between lateral, one-dimensional electron and hole subbands The observed subband separations, \ensuremath{\sim}10 meV, are consistent with the calculated ones
513 citations
TL;DR: In this article, the authors observed visible light emission from nanosize gold clusters and found that relatively intense photoluminescence occurs only when the size of the metal nanocluster is sufficiently small (<5 nm.
Abstract: We have observed visible light emission from nanosize gold clusters. Liquid chromatographic analysis of the metal clusters shows that relatively intense photoluminescence occurs only when the size of the metal nanocluster is sufficiently small (<5 nm). The emission is strongly Stokes shifted and is assigned to radiative recombination of Fermi level electrons and sp- or d-band holes. The electron and/or hole states are perturbed by surface states, as indicated by the dependence of the emission spectrum on the nature of the cluster surface. Finally, we found that large, nonemitting gold clusters can also be made luminescent by partial dissolution using KCN.
512 citations
TL;DR: In this article, the basic theory of the start-up, the exponential growth, and the saturation of the high-gain process is reviewed, emphasizing the self-amplified spontaneous emission.
Abstract: High-gain free-electron lasers (FELs) are being developed as extremely bright sources for a next-generation x-ray facility. In this paper, we review the basic theory of the start-up, the exponential growth, and the saturation of the high-gain process, emphasizing the self-amplified spontaneous emission. The radiation characteristics of an x-ray FEL, including its transverse coherence, temporal characteristics, and harmonic content, are discussed. FEL performance in the presence of machine errors and undulator wakefields is examined. Various enhancement schemes through seeding and beam manipulations are summarized.
509 citations
TL;DR: Spontaneous radiation by an atom in a Rydberg state is inhibited by use of parallel conducting planes to eliminate the vacuum modes at the transition frequency.
Abstract: Spontaneous radiation by an atom in a Rydberg state has been inhibited by use of parallel conducting planes to eliminate the vacuum modes at the transition frequency. Spontaneous emission is observed to "turn off" abruptly at the cutoff frequency of the waveguidelike structure and the natural lifetime is measured to increase by a factor of at least 20.
502 citations