Spontaneous emission

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

Cavity quantum electrodynamics with semiconductor quantum dots: Role of phonon-assisted cavity feeding

Abstract: For a semiconductor quantum dot strongly coupled to a microcavity, we theoretically investigate phonon-assisted transitions from the exciton to a cavity photon, where the energy mismatch is compensated by phonon emission or absorption. By means of a Schrieffer-Wolff transformation we derive an effective Hamiltonian, which describes the combined effect of exciton-cavity and exciton-phonon couplings, and compute the scattering rates within a Fermi-golden-rule approach. The results of this approach are compared with those of a recently reported description scheme based on the independent boson model [U. Hohenester et al., Phys. Rev. B 80, 201311(R) (2009)] and a numerical density-matrix approach. All description schemes are shown to give very similar results. This demonstrates that phonon-assisted cavity feeding can be described in terms of a simple scattering process and does not require a non-Markovian treatment as suggested elsewhere. We present results for the spontaneous emission lifetime of a quantum dot initially populated with a single exciton or biexciton and for the spectral properties of an optically driven dot-cavity system operating in the strong-coupling regime. Our results demonstrate that phonon-assisted feeding plays a dominant role for strongly coupled dot-cavity systems when the detuning is of the order of a few millielectron volts.

Short-pulsed stimulated emission in the powders of NdAl 3 (BO 3 ) 4 , NdSc 3 (BO 3 ) 4 , and Nd:Sr 5 (PO 4 ) 3 F laser crystals

Abstract: Short (>300-ps) pulses of stimulated emission were found from powders of NdAl3(BO3)4, NdSc3(BO3)4, and Nd:Sr5(PO4)3F laser crystals during 532- and 805-nm excitation. Study of stimulated emission in the mixture of two powders has shown that the different components influence each other. That implies a collective behavior of emitting particles. The main features of experimentally observed stimulated emission are described with a simple model accounting for 4F3/2 excited-state concentration and emission energy density. The threshold of stimulated emission in powders is shown to be inversely proportional to the small-signal amplification along the photon path in the pumped volume.

Optical emission from laser-induced breakdown plasma of solid and liquid samples in the presence of a magnetic field.

Abstract: The optical properties of laser-induced plasma generated firm solid (Al alloy) and liquid (Mn, Cr, Mg, or Ti solutions) samples expanded across an external, steady magnetic field have been studied by atomic-emission spectroscopy. Various line emissions obtained from the constituents of the Al alloy and of the aqueous solution show an enhancement in intensity in the presence of an approximately 5-kG magnetic field. The enhancement of the signal was nearly a factor of 2 for the minor constituents of the solid samples and a factor of 1.5 for the elements in liquid phase. Temporal evolution of the emission from the solid sample showed maximum enhancement in emission intensity at 3-10-micros time delay after plasma formation in the laser energy range 10-50 mJ. However, for the liquid sample the maximum signal was for a gate delay of 3-25 micros the energy range 50-200 mJ. This enhancement in the emission intensity was found to be due to an increase in effective density of the plasma as a result of magnetic confinement when the plasma cooled after expansion. This enhanced emission was due to an increase in the rate of radiative recombination in the plasma.

Output power and temperature dependence of the linewidth of single‐ frequency cw (GaAl)As diode lasers

Abstract: We report here the observation of a linear dependence of cw single‐frequency (GaAl)As diode laser linewidth as a function of reciprocal output power at 77, 195, and 273 K. The observed data are explained in terms of spontaneous emission events and their related refractive index perturbations.

Lighting up silicon nanoparticles with Mie resonances.

Abstract: As one of the most important semiconductors, silicon has been used to fabricate electronic devices, waveguides, detectors, solar cells, etc However, the indirect bandgap and low quantum efficiency (10−7) hinder the use of silicon for making good emitters For integrated photonic circuits, silicon-based emitters with sizes in the range of 100−300 nm are highly desirable Here, we show the use of the electric and magnetic resonances in silicon nanoparticles to enhance the quantum efficiency and demonstrate the white-light emission from silicon nanoparticles with feature sizes of ~200 nm The magnetic and electric dipole resonances are employed to dramatically increase the relaxation time of hot carriers, while the magnetic and electric quadrupole resonances are utilized to reduce the radiative recombination lifetime of hot carriers This strategy leads to an enhancement in the quantum efficiency of silicon nanoparticles by nearly five orders of magnitude as compared with bulk silicon, taking the three-photon-induced absorption into account As an indirect semiconductor, silicon shows notoriously inefficient luminescence Here, the authors utilize the Mie resonances in silicon nanoparticles to demonstrate visible white-light emission, both from free-standing spheres and particles etched on a silicon-on-insulator substrate