Spontaneous emission

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

Tunable delay line with interacting whispering-gallery-mode resonators

Abstract: We theoretically study a parallel configuration of two interacting whispering-gallery-mode optical resonators and show a narrowband modal structure as a basis for a widely tunable delay line. For the optimum coupling configuration the system can possess an unusually narrow spectral feature with a much narrower bandwidth than the loaded bandwidth of each individual resonator. The effect has a direct analogy with the phenomenon of electromagnetically induced transparency in quantum systems for which the interference of spontaneous emission results in ultranarrow resonances.

Inhibition, enhancement and control of spontaneous emission in photonic nanowires

Abstract: We experimentally investigate the spontaneous emission (SE) rates of single InAs quantum dots embedded in GaAs photonic nanowires. For a diameter leading to the optimal confinement of the fundamental guided mode HE11, the coupling to HE11 dominates the SE process and an increase of the SE rate by a factor of 1.5 is achieved. When the diameter is decreased, the coupling to this mode vanishes rapidly, thus allowing the coupling to the other radiation modes to be probed. In these conditions, a SE inhibition factor of 16, equivalent to the one obtained in state-of-the-art photonic crystals, is measured. These results, which are supported by fully vectorial calculations, confirm the potential of photonic nanowires for a nearly perfect, broadband SE control.

Measuring and Modifying the Spontaneous Emission Rate of Erbium near an Interface

Abstract: Spontaneous emission is interpreted as a consequence of interaction between matter and electromagnetic radiation. Previous experiments, using for instance Rydberg atoms or semiconductor structures, have demonstrated that spontaneous emission can be influenced in cavities or near mirrors [1 ‐ 7]. In this Letter we will show an extremely simple way to modify the spontaneous emission rate, merely by bringing liquid films with certain refractive index in contact with a silica glass surface which is locally doped with luminescent Er 31 ions. Erbium shows clear photoluminescence (PL) around 1.54 mm [8], an important wavelength in optical telecommunication [9]. The theoretical description of spontaneous emission is usually based on concepts from quantum electrodynamics such as vacuum fluctuations and a creation and annihilation formalism. The inclusion of a dielectric interface requires special attention [10]. In this case, the variation in the spontaneous emission rate can be accounted for by the local classical density of states (DOS), which appears in Fermi’s golden rule. In this Letter, a straightforward calculation of the local DOS is performed, given the Fresnel equations for transmission and refraction at a dielectric interface. The analysis describes our data on the modification of the spontaneous emission rate as a function of refractive index, and serves to determine for the first time the radiative lifetime of Er in silicate glass, a parameter of great importance for Er-doped optical gain materials in telecommunication technology. Two samples of bulk sodalime silicate glass (refractive index n0 › 1.5) were implanted with 500 keV Er ions. Sample A was covered with a 120 nm thick Al film as a stopping layer, and sample B was uncovered during implantation. After implantation, the Al layer was etched off, and a thermal anneal at 512 ‐ C was performed. Erbium depth profiles for both samples, as determined using 2 MeV 4 He 1 Rutherford backscattering spectrometry (RBS), are shown in Fig. 1. The open data points for sample A show a profile peaked at the glass surface, with a half-width of 70 nm. The measured profile is a convolution of the detection resolution and the actual profile which is discontinuous at the surface. The drawn line shows the deconvoluted profile, which has a surface concentration of , 0.25 at. %. The solid data points in Fig. 1 show a Gaussian profile for sample B, centered at 150 nm depth from the surface, where the Er concentration is 0.17 at. %. The full width at half maximum is 100 nm. PL spectroscopy was carried out at room temperature. The 514.5 nm line of an Ar-ion laser was used to excite the Er, and the luminescence was spectrally analyzed with a monochromator and detected with a liquid-nitrogen cooled Ge detector. PL decay measurements were performed after exciting with a 1.5 ms pulse, using a digital averaging oscilloscope. Further details on sample preparation and PL measurements can be found in Ref. [11]. Various liquids, with refractive indices ranging from 1.3 to 1.7, and thickness in the order of a mm, were brought in contact with the sample surface on the front, while the luminescence signal was collected on the back side (see inset in Fig. 2).

Exciton localization in InGaN quantum well devices

Abstract: Emission mechanisms of a device-quality quantum well (QW) structure and bulk three dimensional (3D) InGaN materials grown on sapphire substrates without any epitaxial lateral overgrown GaN base layers were investigated. The InxGa1−xN layers showed various degrees of in-plane spatial potential (band gap) inhomogeneity, which is due to a compositional fluctuation or a few monolayers thickness fluctuation. The degree of fluctuation changed remarkably around a nominal InN molar fraction x=0.2, which changes to nearly 0.08–0.1 for the strained InxGa1−xN. This potential fluctuation induces localized energy states both in the QW and 3D InGaN, showing a large Stokes-like shift. The spontaneous emission from undoped InGaN single QW light-emitting diodes (LEDs), undoped 3D LEDs, and multiple QW (MQW) laser diode (LD) wafers was assigned as being due to the recombination of excitons localized at the potential minima, whose lateral size was determined by cathodoluminescence mapping to vary from less than 60 to 300 nm...

Light interference from single atoms and their mirror images.

Abstract: A single atom emitting single photons is a fundamental source of light. But the characteristics of this light depend strongly on the environment of the atom1,2. For example, if an atom is placed between two mirrors, both the total rate and the spectral composition of the spontaneous emission can be modified. Such effects have been observed using various systems: molecules deposited on mirrors3, dye molecules in an optical cavity4, an atom beam traversing a two-mirror optical resonator5,6,7,8, single atoms traversing a microwave cavity9,10,11 and a single trapped electron12. A related and equally fundamental phenomenon is the optical interaction between two atoms of the same kind when their separation is comparable to their emission wavelength. In this situation, light emitted by one atom may be reabsorbed by the other, leading to cooperative processes in the emission13,14. Here we observe these phenomena with high visibility by using one or two single atom(s), a collimating lens and a mirror, and by recording the individual photons scattered by the atom(s). Our experiments highlight the intimate connection between one-atom and two-atom effects, and allow their continuous observation using the same apparatus.