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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 surface plasmon-enhanced spontaneous emission based on an organic light-emitting device is reported in this article, where silver nanoparticles were thermally deposited in a high vacuum on cathode that had a 1-nm-thick LiF spacer.
Abstract: The surface plasmon-enhanced spontaneous emission based on an organic light-emitting device is reported in this paper. For surface plasmon localization, silver nanoparticles were thermally deposited in a high vacuum on cathode that had a 1-nm-thick LiF spacer. Since plasmons provide a strong oscillator decay channel, time-resolved photoluminescence (PL) results displayed a 1.75-fold increased emission rate, and continuous wave PL results showed a twofold enhanced intensity. In addition, LiF film/Ag cluster/LiF film structure resolved the carrier injection problem between the cathode and the organic layer. Thus, the suggested design may follow plasmonic applications for a wider organic optoelectronics.

111 citations

Journal ArticleDOI
TL;DR: The time and space resolved dynamics of a qubit with an Ohmic coupling to propagating 1D photons is studied, from weak coupling to the ultrastrong coupling regime.
Abstract: The time and space resolved dynamics of a qubit with an Ohmic coupling to propagating 1D photons is studied, from weak coupling to the ultrastrong coupling regime. A nonperturbative study based on matrix product states shows the following results, (i) The ground state of the combined systems contains excitations of both the qubit and the surrounding bosonic field. (ii) An initially excited qubit equilibrates through spontaneous emission to a state, which under certain conditions is locally close to that ground state, both in the qubit and the field. (iii) The resonances of the combined qubit-photon system match those of the spontaneous emission process and also the predictions of the adiabatic renormalization [A. J. Leggett et al., Rev. Mod. Phys. 59, 1 (1987)]. Finally, nonperturbative ab initio calculations show that this physics can be studied using a flux qubit galvanically coupled to a superconducting transmission line.

111 citations

Journal ArticleDOI
TL;DR: In this article, the authors proposed a nanowire (NW)-based nanolasers utilizing AlGaInN materials system, which are an emerging and promising area of research.
Abstract: One-dimensional compound semiconductor nanolasers, especially nanowire (NW)-based nanolasers utilizing III-nitride (AlGaInN) materials system, are an emerging and promising area of research. Significant achievements have been made in developing III-nitride NW lasers with emission wavelengths from the deep ultraviolet (UV) to the near-infrared spectral range. The types of lasers under investigation include Fabry-Perot, photonic crystal, plasmonic, ring resonator, microstadium, random, polariton, and two-dimensional distributed feedback lasers. The lasing thresholds vary by several orders of magnitude, which are a direct consequence of differing NW dimensions, quality of the NWs, characteristics of NW cavities, and coupling with the substrate. For electrically injected, such as ultralow-threshold and continuous-wave III-nitride NW lasers that can operate at room temperature, the following obstacles remain: carrier loss mechanisms including defect-related nonradiative surface recombination, electron overflow, and poor hole transport; low radiative recombination efficiency and high surface recombination; poor thermal management; and highly resistive ohmic contacts on the p -layer. These obstacles must be overcome to fully realize the potential of these lasers.

111 citations

Journal ArticleDOI
TL;DR: In this article, the effect of bandwidth and coherence properties of the excitation source on the decay and dephasing of isolated large molecules was studied using three different excitation sources, a single mode dye laser, a multimode dye laser and an incoherent N2 flash lamp.
Abstract: One purpose of this paper is to present new studies on the effect of bandwidth and the coherence properties of the excitation source on the decay and the dephasing of isolated large molecules. A detailed study of the system pentacene in a p-terphenyl matrix is presented utilizing three different excitation sources, a single mode dye laser (60 KHz–6 MHz bandwidth depending on the time scale of the experiment) a multimode dye laser (240 GHz bandwidth), and an incoherent N2 flash lamp. Optical T1 (the longitudinal relaxation time) and T2 (the transverse relaxation time) are measured from the coherent and incoherent transients observed either in the forward direction of the laser or at right angles to the exciting beam. At 1.8 °K, the optical transition (1A1g-->1B2u) of pentacene in p-terphenyl exhibits four sites, the lowest of which at 16 887 cm−1 has the following parameters: T2=44±2 nsec; T1=24.9±2 nsec, and µ=0.7±0.1 D. The transition moment µ, is obtained directly from the optical nutation, which exhibits a Rabi nutation time (h-slash/µ·epsilon) of 27.3 nsec, and is corrected for the effect of the Lorentz local field inside the terphenyl crystal. The experiments presented here are categorized into two time regimes for theoretical analysis; a transient coherence regime where the observed decay is comparable with (h-slash/µ·epsilon) and T2, and a steady-state coherence regime where transient dephasing is complete and the off-diagonal elements of the density matrix have decayed to their steady-state values in the presence of the field of amplitude epsilon. Using the Wilcox–Lamb method, rate equations (with T2 expressions) describing the population flow in the ''complete'' level structure of pentacene (ground||0>, singlet ||p>, and triplet {||l}) are derived from the density matrix equations of motion. When these equations are averaged over the inhomogeneous width of the optical transition and the measured Gaussian transverse profile of our laser we obtain T1p0=24.9±2 nsec and T1pl=15.7 µsec, the time constants by which pentacene spontaneously decays to ||0> or crosses over into l, as well as the averaged population at time t. In an effort to be complete, attention is placed upon the relationship between theory and the experimental findings. First, expressions for the OFID and nutation in the solid are presented for the pentacene case in order to relate T1, T2, and µ to the level structure. Second, at low temperatures (1.8 °K), the origin of dephasing is identified as spontaneous emission from p-->0 since experimentally T2?2T1, in agreement with other work. At higher temperature, however, a strongly temperature dependent dephasing process with an onset at 3.7 °K takes place. Armed with these observations we present a theoretical treatment of these distinct dephasing channels and their temperature dependences. A discussion regarding the influence of ''accepting'' phonon modes (either optical or acoustic) on optical dephasing is also given. The results indicate that the treatment of Jones et al. can (1) explain the observed temperature dependence of T2 in pentacene; (2) distinguish dephasing as a result of scattering by acoustic phonons from that due to resonance or quasilocalized phonons with clear connections to gas and liquid state theories, but without invoking more than two approximation levels. (3) explain both the level shift and line width changes as a result of ''conventional'' dephasing or dephasing by exchange mechanisms; and (4) relate the pure dephasing term to an anisotropy in the scattering amplitudes (between the ground and excited states in the system) which contribute largely to the homogeneous width of the transition. Optical site selection of these transitions is also reported and discussed in relation to vibrational relaxation and to both homogeneous and inhomogeneous broadenings. The studies of the homogeneous broadening of the vibronic origin (267 cm−1) indicate that vibrational relaxation is fast (psec) in the excited singlet manifold of pentacene. Finally from more than ten independent experiments including single and multimode excitation, on- and off-resonance scattering, Zeeman effect and the transient decay as a function of excess energy in the molecule, a more complete picture of the pentacene level structure {||l>} is given. With this in mind, the influence of the laser bandwidth and coherence properties on state preparation and subsequent dephasing and decay is concluded. It is proposed that the slow decay, (~15 µsec) observed during narrow-band excitation represents intersystem crossing to nearby triple manifolds after the transient coherence of the 0 p subsystem is decayed. In addition, the decay of the primary state prepared in these experiments is not sensitive to the bandwidth or the correlation time of our excitation sources.

111 citations

Journal ArticleDOI
TL;DR: In this paper, a transmon qubit is coupled to a superconducting metamaterial with a deep sub-wavelength lattice constant (λ/60), which is formed by periodically loading a transmission line with compact, low-loss, low disorder lumped-element microwave resonators.
Abstract: Embedding tunable quantum emitters in a photonic bandgap structure enables control of dissipative and dispersive interactions between emitters and their photonic bath. Operation in the transmission band, outside the gap, allows for studying waveguide quantum electrodynamics in the slow-light regime. Alternatively, tuning the emitter into the bandgap results in finite-range emitter–emitter interactions via bound photonic states. Here, we couple a transmon qubit to a superconducting metamaterial with a deep sub-wavelength lattice constant (λ/60). The metamaterial is formed by periodically loading a transmission line with compact, low-loss, low-disorder lumped-element microwave resonators. Tuning the qubit frequency in the vicinity of a band-edge with a group index of ng = 450, we observe an anomalous Lamb shift of −28 MHz accompanied by a 24-fold enhancement in the qubit lifetime. In addition, we demonstrate selective enhancement and inhibition of spontaneous emission of different transmon transitions, which provide simultaneous access to short-lived radiatively damped and long-lived metastable qubit states.

111 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202383
2022213
2021360
2020338
2019419
2018453