Spontaneous emission

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

Superabsorption of light via quantum engineering

Abstract: Almost 60 years ago Dicke introduced the term superradiance to describe a signature quantum effect: N atoms can collectively emit light at a rate proportional to N(2). Structures that superradiate must also have enhanced absorption, but the former always dominates in natural systems. Here we show that this restriction can be overcome by combining several well-established quantum control techniques. Our analytical and numerical calculations show that superabsorption can then be achieved and sustained in certain simple nanostructures, by trapping the system in a highly excited state through transition rate engineering. This opens the prospect of a new class of quantum nanotechnology with potential applications including photon detection and light-based power transmission. An array of quantum dots or a molecular ring structure could provide a suitable platform for an experimental demonstration.

Design and characteristics of staggered InGaN quantum-well light-emitting diodes in the green spectral regime

Abstract: Staggered InGaN quantum wells (QWs) are investigated both numerically and experimentally as improved active region for light-emitting diodes (LEDs) emitting at 520–525 nm. Based on a self-consistent six-band k·p method, band structures of both two-layer staggered InxGa1−xN/InyGa1−yN QW and three-layer staggered InyGa1−yN/InxGa1−xN/InyGa1−yN QW structures are investigated as active region to enhance the spontaneous emission radiative recombination rate (Rsp) for LEDs emitting at 520–525 nm. Numerical analysis shows significant enhancement of Rsp for both two-layer and three-layer staggered InGaN QWs as compared to that of the conventional InzGa1−zN QW. Significant reduction of the radiative carrier lifetime contributes to the enhancement of the radiative efficiency for both two-layer and three-layer staggered InGaN QW LEDs emitting at 520–525 nm. Three-layer staggered InGaN QW LEDs emitting at 520–525 nm was grown by metal-organic chemical vapour deposition (MOCVD) by employing graded-temperature profile. Power density-dependent cathodoluminescence (CL) measurements show the enhancement of peak luminescence by up to 3 times and integrated luminescence by 1.8–2.8 times for the three-layer staggered InGaN QW LED. Electroluminescence (EL) output power of the staggered InGaN QW LED exhibits 2.0–3.5 times enhancement as compared to that of the conventional InGaN QW LED. The experimental results show the good agreement with theory.

Active Tuning of Spontaneous Emission by Mie-Resonant Dielectric Metasurfaces

Abstract: Mie-resonant dielectric metasurfaces offer comprehensive opportunities for the manipulation of light fields with high efficiency. Additionally, various strategies for the dynamic tuning of the optical response of such metasurfaces were demonstrated, making them important candidates for reconfigurable optical devices. However, dynamic control of the light-emission properties of active Mie-resonant dielectric metasurfaces by an external control parameter has not been demonstrated so far. Here, we experimentally demonstrate the dynamic tuning of spontaneous emission from a Mie-resonant dielectric metasurface that is situated on a fluorescent substrate and embedded into a liquid crystal cell. By switching the liquid crystal from the nematic state to the isotropic state via control of the cell temperature, we induce a shift of the spectral position of the metasurface resonances. This results in a change of the local photonic density of states, which, in turn, governs the enhancement of spontaneous emission fro...

Low-threshold topological nanolasers based on second-order corner state.

Abstract: The topological lasers, which are immune to imperfections and disorders, have been recently demonstrated based on many kinds of robust edge states, being mostly at microscale. The realization of 2D on-chip topological nanolasers, having the small footprint, low threshold and high energy efficiency, is still to be explored. Here, we report on the first experimental demonstration of the topological nanolaser with high performance in 2D photonic crystal slab. Based on the generalized 2D Su-Schrieffer-Heeger model, a topological nanocavity is formed with the help of the Wannier-type 0D corner state. Laser behaviors with low threshold about 1 $\mu W$ and high spontaneous emission coupling factor of 0.25 are observed with quantum dots as the active material. Such performance is much better than that of topological edge lasers and comparable to conventional photonic crystal nanolasers. Our experimental demonstration of the low-threshold topological nanolaser will be of great significance to the development of topological nanophotonic circuitry for manipulation of photons in classical and quantum regimes.

Ultrafast switching of photonic density of states in photonic crystals

Abstract: It is shown theoretically that the photonic density of states (DOS) of three-dimensional semiconductor photonic crystals can be dramatically changed on ultrafast time scales through two photon excitation of free carriers. Calculations for GaAs inverse opals show that the photonic band gap exhibits a large shift in frequency and a change in width with an appropriate excitation pulse. At certain frequencies, the DOS can be switched from a high value to zero, from zero to a high value, and from a high to zero to a high on 100-fs time scales, independent of the relaxation time of the semiconductor. This technique allows for ultrafast control of spontaneous emission and trapping of photons.