Search results for " Spontaneous emission"
showing 10 items of 55 documents
Control of nonlinear processes in two-photon excited rubidium vapour by resonant laser light
2019
Frequency up- and down-conversion in warm alkali vapours over a range of applied cw laser intensities has received much attention in recent years due to promising applications in the fields of remote detection, quantum information and computing, specifically in the implementation of correlated photon pairs, photon storage and quantum memory interface to name a few. The generation of directional laser-like blue and infrared light in alkali vapours has been extensively studied. However, important details of the interplay of parametric and nonparametric nonlinear processes, such as the four-wave mixing (FWM) and amplified spontaneous emission (ASE) responsible for the new field generation, are…
Modulational instability in fiber systems with periodic loss compensation and dispersion management
2003
In this paper we study modulational instability in a Kerr fiber taking into account the combined effects of periodic power variations and dispersion management. It is shown that periodic dispersion management and periodic amplification produce nonconventional MI sidebands which are essentially independent of each other. In addition, we show that the amplifier spontaneous emission noise tends to inhibit the growth of sidebands, for a sufficiently long propagation distance.
Duty-ratio control of Nonlinear phase noise in dispersion-managed WDM transmissions using RZ-DPSK modulation at 10 Gb/s
2006
International audience; The authors compare analytical and numerical estimates, showing that the nonlinear phase noise of short optical pulses associated with the coupling between amplified spontaneous emission noise and fiber nonlinearity may be controlled by adjusting the duty cycle of the return-to-zero (RZ) signal modulation format. The impact of this effect in the optimization of the performance of 10-Gb/s dispersion-managed wavelength division multiplexed (WDM) systems using RZ-differential phase-shift keying (DPSK) modulation is discussed. By extensive numerical simulations, it is shown that the transmission quality of ultradense WDM systems using the RZ-DPSK modulation format may be…
Control of spontaneous emission of a single quantum emitter through a time-modulated photonic-band-gap environment
2017
We consider the spontaneous emission of a two-level quantum emitter, such as an atom or a quantum dot, in a modulated time-dependent environment with a photonic band gap. An example of such an environment is a dynamical photonic crystal or any other environment with a bandgap whose properties are modulated in time, in the effective mass approximation. After introducing our model of dynamical photonic crystal, we show that it allows new possibilities to control and tailor the physical features of the emitted radiation, specifically its frequency spectrum. In the weak coupling limit and in an adiabatic case, we obtain the emitted spectrum and we show the appearance of two lateral peaks due to…
Emergence of non-Markovianity in the emission process of an atom in a half-cavity
2014
We study quantum non-Markovianity in the early stage of the emission process of a two-level atom coupled to a semi-infinite waveguide, where the waveguide termination behaves as a perfect mirror. Specifically, we restrict to the analysis of the process for times shorter than twice the time delay t_d, where t_d is the duration of a round trip along the atom-mirror path. We show the emergence of a threshold in the parameters space separating the Markovian and non-Markovian regions.
Intermittent decoherence blockade in a chiral ring environment
2021
It has long been recognized that emission of radiation from atoms is not an intrinsic property of individual atoms themselves, but it is largely affected by the characteristics of the photonic environment and by the collective interaction among the atoms. A general belief is that preventing full decay and/or decoherence requires the existence of dark states, i.e., dressed light-atom states that do not decay despite the dissipative environment. Here, we show that, contrary to such a common wisdom, decoherence suppression can be intermittently achieved on a limited time scale, without the need for any dark state, when the atom is coupled to a chiral ring environment, leading to a highly non-e…
Complex quantum state generation and coherent control based on integrated frequency combs
2019
The investigation of integrated frequency comb sources characterized by equidistant spectral modes was initially driven by considerations towards classical applications, seeking a more practical and miniaturized way to generate stable broadband sources of light. Recently, in the context of scaling the complexity of optical quantum circuits, these on-chip approaches have provided a new framework to address the challenges associated with non-classical state generation and manipulation. For example, multi-photon and high-dimensional states were to date either inaccessible, lacked scalability, or were difficult to manipulate, requiring elaborate approaches. The emerging field of quantum frequen…
Dynamics of spontaneous emission in a single-end photonic waveguide
2012
We investigate the spontaneous emission of a two-level system, e.g. an atom or atomlike object, coupled to a single-end, i.e., semi-infinite, one-dimensional photonic waveguide such that one end behaves as a perfect mirror while light can pass through the opposite end with no back-reflection. Through a quantum microscopic model we show that such geometry can cause non-exponential and long-lived atomic decay. Under suitable conditions, a bound atom-photon stationary state appears in the atom-mirror interspace so as to trap a considerable amount of initial atomic excitation. Yet, this can be released by applying an atomic frequency shift causing a revival of photon emission. The resilience of…
Dynamic Characterization of Upconversion in Highly Er-Doped Silica Photonic Crystal Fibers
2012
Measurements of time evolution of amplified spontaneous emission for square-wave modulated pump were made on a highly erbium-doped silica photonic crystal fiber and fitted to theoretical results calculated using different formalisms to describe the ${\rm Er}^{3+}$ -ion migration-assisted co-operative upconversion mechanism in the population densities rate equations. The determined characterization parameters are the constant homogeneous upconversion coefficient, 3.0 $\times 10^{-24}~{\rm m}^{3}/{\rm s}$ , the critical radii for upconversion and migration, 10.5 and 14A, respectively, and the rate of clustered ions, 14%. These parameters are analysed and compared to those obtained with contin…
Several Derivatives of 6-(Tert-Butyl)-4H-Pyran-4-Ylidene Malononitrile with Different Amorphous Phase Promoting Substituents for Light-Amplification …
2019
A series of glassy 6-(tert-butyl)-4H-pyran-4-ylidene malononitrile (DCM) derivatives with covalently attached amorphous state promoting bulky 1,1,1-triphenylmethyl (trityl) moieties through several chemical design approaches have been synthesized and investigated for suitability in organic solid state laser applications. Results showed that the bonding type of such functional groups had a considerable influence on glass structure forming dye thermal properties and a slight influence on their optical properties. Thermal stability up to 346 °C was achieved with glass transitions in the range from 39 to 138 °C. Incorporation of bulky triphenyl substituents via ester groups showed remarkable am…