Spontaneous emission

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

Highly indistinguishable on-demand resonance fluorescence photons from a deterministic quantum dot micropillar device with 74% extraction efficiency.

Abstract: The implementation and engineering of bright and coherent solid state quantum light sources is key for the realization of both on chip and remote quantum networks. Despite tremendous efforts for more than 15 years, the combination of these two key prerequisites in a single, potentially scalable device is a major challenge. Here, we report on the observation of bright single photon emission generated via pulsed, resonance fluorescence conditions from a single quantum dot (QD) deterministically centered in a micropillar cavity device via cryogenic optical lithography. The brightness of the QD fluorescence is greatly enhanced on resonance with the fundamental mode of the pillar, leading to an overall device efficiency of η = (74 ± 4) % for a single photon emission as pure as g(2)(0) = 0.0092 ± 0.0004. The combination of large Purcell enhancement and resonant pumping conditions allows us to observe a two-photon wave packet overlap up to ν = (88 ± 3) %.

Electrically pumped ZnO film ultraviolet random lasers on silicon substrate

Abstract: The electrically pumped ultraviolet (UV) random lasing in c-axis oriented ZnO polycrystalline films has been demonstrated. For this demonstration, a metal-oxide-semiconductor structure of Au∕SiOx(x<2)∕ZnO film was fabricated on a silicon substrate. With ever-higher forward bias where the negative voltage was connected to the silicon substrate, the UV electroluminescence from such a ZnO-based device transformed from the spontaneous emission to the random lasing in the ZnO film. It is believed that the recurrent scattering and interference of the enough strong electroluminescent UV light in the in-plane random cavities formed in the ZnO film leads to electrically pumped UV random lasing.

The quantum fluctuations of the optical parametric oscillator. i.

Abstract: Our treatment is based on a microscopically correct Hamiltonian which contains the Bose-operators of the light modes and the Fermi-operators of the optically active electrons in the medium. The coupling between modes and atoms is taken from quantum-electrodynamics. Besides that, the light modes may interact with external “heat baths” like the mirrors, scattering centers etc., while the atoms interact with lattice vibrations, incoherent light fields etc. Using recently developed methods the effect of these heatbaths is taken into account in a quantum mechanically consistent fashion. In the present paper we apply quantum mechanical Langevin equations for the field and electron operators which contain dissipation and fluctuation terms. The elimination of the electron operators by an iteration procedure finally leaves us with a set of coupled nonlinear field equations which are shown to be quantum mechanically consistent. They are solved in the Heisenberg picture below threshold by linearization and well above threshold by quantum mechanical quasi-linearization. The solutions show that the line width of the signal mode below threshold is due to the vacuum fluctuations in the idler and vice versa, whereas the thermal noise of the resonator and the spontaneous emission noise of the medium may be neglected. Above threshold the linewidth is caused by the undamped diffusion of the phase difference between signal and idler, to which the vacuum fluctuations of both modes contribute in equal parts. The phase sum of both modes adiabatically follows the slow phase diffusion of the external pump light, produced by a laser, and therefore contributes to the linewidth too. Well above threshold the amplitudes are stable. Correlation and cross-correlation functions of their small residual fluctuations are calculated.

Efficient excitation of a two-level atom by a single photon in a propagating mode

Abstract: State mapping between atoms and photons, and photon-photon interactions play an important role in scalable quantum information processing. We consider the interaction of a two-level atom with a quantized propagating pulse in free space and study the probability ${P}_{e}(t)$ of finding the atom in the excited state at any time $t$. This probability is expected to depend on (i) the quantum state of the pulse field and (ii) the overlap between the pulse and the dipole pattern of the atomic spontaneous emission. We show that the second effect is captured by a single parameter $\ensuremath{\Lambda}\ensuremath{\in}[0,8\ensuremath{\pi}/3]$, obtained by weighting the dipole pattern with the numerical aperture. Then, ${P}_{e}(t)$ can be obtained by solving time-dependent Heisenberg-Langevin equations. We provide detailed solutions for both single-photon Fock state and coherent states and for various temporal shapes of the pulses.

Optical Properties of Rare-Earth Ions in Lead Germanate Glasses

Abstract: Glasses of composition (x - 1)PbO(100 - x)GeO21Ln2O3, with x= 30 mol% (Ln = Nd, Eu, Er), 40 mol% (Ln = Pr, Nd, Sm, Eu, Dy, Ho, Er, Tm), and 50 mol% (Ln = Eu, Er), have been prepared by quenching the oxidic melts. From the optical absorption and emission spectra in the ultraviolet-visible-near-infrared (UV-VIS-NIR) region, the intensity parameters, spontaneous emission probabilities, branching ratios, radiative lifetimes, and, for selected NIR transitions, peak stimulated emission cross sections have been obtained. The trends observed in the intensity parameters have been discussed, as a function of the number of f electrons as well as a function of the lead content. As the amount of lead increases, the covalency of the Ln-O bond increases, the symmetry of the rare-earth site increases, and the dopant site distribution narrows. The peak stimulated emission cross sections rank among the highest found for oxide glasses.