Spontaneous emission

About: Spontaneous emission is a research topic. Over the lifetime, 12855 publications have been published within this topic receiving 323684 citations.

Temperature dependence of polaronic transport through single molecules and quantum dots

Abstract: Motivated by recent experiments on electric transport through single molecules and quantum dots, we investigate a model for transport that allows for significant coupling between the electrons and a boson mode isolated on the molecule or dot. We focus our attention on the temperature-dependent properties of the transport. In the Holstein picture for polaronic transport in molecular crystals the temperature dependence of the conductivity exhibits a crossover from coherent (band) to incoherent (hopping) transport. Here, the temperature dependence of the differential conductance on resonance does not show such a crossover, but is mostly determined by the lifetime of the resonant level on the molecule or dot.

Partly gain-coupled 1.55 mu m strained-layer multiquantum-well DFB lasers

Abstract: 1.55- mu m gain-coupled InGaAsP-InP distributed feedback (DFB) lasers which use a strained-layer multi-quantum-well (MQW) active grating for a mixed index and gain coupling have been fabricated and studied. The lasers exhibit distinct longitudinal-mode behaviour due to gain-coupling effects, including a high single-mode yield. Cavity length dependence of the mode behavior has been experimentally studied and simulated using a transfer-matrix method. Both experimental and theoretical results indicate that the shorter cavity lasers with the present structure have higher kappa /sub gain/L/ kappa /sub inde/ ratios and wider Fabry-Perot mode spacing than the longer cavity ones; these features enable the shorter cavity lasers to have a high single-mode yield (90%) and a high side-mode-suppression ratio (55 dB). >

Ground State Electroluminescence

Abstract: Electroluminescence, the emission of light in the presence of an electric current, provides information on the allowed electronic transitions of a given system. It is commonly used to investigate the physics of strongly coupled light-matter systems, whose eigenfrequencies are split by the strong coupling with the photonic field of a cavity. Here we show that, together with the usual electroluminescence, systems in the ultrastrong light-matter coupling regime emit a uniquely quantum radiation when a flow of current is driven through them. While standard electroluminescence relies on the population of excited states followed by spontaneous emission, the process we describe herein extracts bound photons from the dressed ground state and it has peculiar features that unequivocally distinguish it from usual electroluminescence.

Spontaneous emission of matter waves from a tunable open quantum system

Abstract: The decay of an excited atom undergoing spontaneous photon emission into the fluctuating quantum-electrodynamic vacuum is an emblematic example of the dynamics of an open quantum system. Recent experiments have demonstrated that the gapped photon dispersion in periodic structures, which prevents photons in certain frequency ranges from propagating, can give rise to unusual spontaneous-decay behaviour, including the formation of dissipative bound states1–3. So far, these effects have been restricted to the optical domain. Here we demonstrate similar behaviour in a system of artificial emitters, realized using ultracold atoms in an optical lattice, which decay by emitting matter-wave, rather than optical, radiation into free space. By controlling vacuum coupling and the excitation energy, we directly observe exponential and partly reversible non-Markovian dynamics and detect a tunable bound state that contains evanescent matter waves. Our system provides a flexible platform for simulating open-system quantum electrodynamics and for studying dissipative many-body physics with ultracold atoms4–6. An open quantum system containing ultracold rubidium atoms trapped in an optical lattice undergoes spontaneous emission of matter waves into free space.

Purcell-factor-enhanced scattering from Si nanocrystals in an optical microcavity.

Abstract: Scattering processes in an optical microcavity are investigated for the case of silicon nanocrystals embedded in an ultra-high-Q toroid microcavity. Using a novel measurement technique based on the observable mode splitting, we demonstrate that light scattering is highly preferential: more than 99.8% of the photon flux is scattered into the original doubly degenerate cavity modes. The large capture efficiency is shown to result from the Purcell enhancement of the optical density of states over the free space value, an effect that is more typically associated with spontaneous emission. The experimentally determined Purcell factor has a lower bound of 171.