Spontaneous emission

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

Ultrasmall and ultralow threshold GaInAsP-InP microdisk injection lasers: design, fabrication, lasing characteristics, and spontaneous emission factor

Abstract: We have calculated lasing characteristics of current injection microdisk lasers of several microns in diameter, taking account of the scattering loss at center posts and the carrier diffusion effect. We found that the optimum width of the disk wing exposed to the air is 0.6-0.7 /spl mu/m and the minimum threshold current is nearly 10 /spl mu/A for the disk diameter of 2 /spl mu/m. The internal differential quantum efficiency can be 95% if the transparent carrier density is reduced to 7.5/spl times/10/sup 17/ cm/sup -3/ and the diffusion constant is increased to 8 cm/sup 2//s. In the experiment, we have obtained the room temperature continuous-wave operation of a GaInAsP-InP device of 3 /spl mu/m in diameter, for the first time, with a record low threshold of 150 /spl mu/A. This achievement was mainly owing to the reduction of the scattering loss at the disk edge, and hence the reduction of the threshold current density. The spontaneous emission factor was estimated to be 6/spl times/10/sup -3/. This value was much reduced by the large detuning of the lasing wavelength against the spontaneous emission peak. A larger value over 0.1, which is expected for such a small device, will be obtained by the wavelength tuning and the narrowing of the spontaneous emission spectrum.

One-atom lasers.

Abstract: One-atom lasers are important because their governing equations can be solved exactly, even with a quantized field. We present a fully quantum-mechanical treatment of one-atom lasers modeled by quantum-optical master equations. These are solved numerically without any significant approximations. We show that laser action is possible with one atom, and that it might be achievable experimentally. Laser action is characterized by the dominance of stimulated emission over spontaneous emission. We use the one-atom laser model to investigate, without approximation, some interesting generic laser phenomena. Under certain conditions lasers produce intensity squeezed light, and then the laser linewidth increases with the pumping rate, in contrast with standard lasers. We also report ``self-quenching'' behavior: lasers with incoherent pumping out of the lower laser level turn off when the pumping is sufficiently fast because the coherence between the laser levels is destroyed.

Electrical control of spontaneous emission and strong coupling for a single quantum dot

Abstract: We report the design, fabrication and optical investigation of electrically tunable single quantum dots—photonic crystal defect nanocavities operating in both the weak and strong coupling regimes of the light–matter interaction. Unlike previous studies where the dot–cavity spectral detuning was varied by changing the lattice temperature, or by the adsorption of inert gases at low temperatures, we demonstrate that the quantum-confined Stark effect can be employed to quickly and reversibly switch the dot–cavity coupling simply by varying a gate voltage. Our results show that exciton transitions from individual dots can be tuned by ~4 meV relative to the nanocavity mode before the emission quenches due to carrier tunneling escape. This range is much larger than the typical linewidth of the high-Q cavity modes (~100 μeV) allowing us to explore and contrast regimes where the dots couple to the cavity or decay by spontaneous emission into the two-dimensional photonic bandgap. In the weak-coupling regime, we show that the dot spontaneous emission rate can be tuned using a gate voltage, with Purcell factors ≥7. New information is obtained on the nature of the dot–cavity coupling in the weak coupling regime, and electrical control of zero-dimensional polaritons is demonstrated for the highest-Q cavities (Q≥12 000). Vacuum Rabi splittings up to ~120 μeV are observed, larger than the linewidths of either the decoupled exciton (γ≤40 μeV) or cavity mode. These observations represent a voltage switchable optical nonlinearity at the single photon level, paving the way towards on-chip dot-based nano-photonic devices that can be integrated with passive optical components.

Plasmon Nanoparticle Array Waveguides for Single Photon and Single Plasmon Sources

Abstract: This Letter discusses how linear coupled plasmon particle arrays inspired by radio frequency Yagi-Uda antennas can be used to construct both efficient unidirectional single photon sources and efficient directional single plasmon sources. Calculations using an exact multipole expansion method are presented of the spontaneous emission directivity, efficiency, and spontaneous emission decay rates, taking into account material loss in real noble metals. An analysis of the emission properties in terms of the dispersion relation of infinite arrays reveals how one can use guided mode dispersion to achieve desirable figures of merit. The key ingredient is to couple the source to array eigenmodes that are just beyond the light line but still wave vector matched to propagating modes to within the momentum uncertainty set by the inverse antenna length. Finally, this Letter shows that the emission decay rates can be controlled independently of the directionality and without penalty in quantum efficiency.

Frequency-Dependent Spontaneous Emission Rate from CdSe and CdTe Nanocrystals: Influence of Dark States

Abstract: We studied the rate of spontaneous emission from colloidal CdSe and CdTe nanocrystals at room temperature. The decay rate, obtained from luminescence decay curves, increases with the emission frequency in a supralinear way. This dependence is explained by the thermal occupation of dark exciton states at room temperature, giving rise to a strong attenuation of the rate of emission. The supralinear dependence is in agreement with the results of tight-binding calculations.