Resonance Fluorescence Spectrum Research Articles

Insights into Fano-type resonance fluorescence from quantum-dot–metal-nanoparticle molecules with a squeezed vacuum

Metal nanoparticles (MNPs) possess the intriguing property of enhancing and limiting the energy of light field to subwavelength scale, which have attracted extensive attention in physics, chemistry, and life sciences. Meanwhile, squeezing is a general concept in quantum optics and can be used to engineer matter interaction scenarios. Here we consider an artificial hybrid molecule consisting of an MNP interacting with a semiconductor quantum dot (QD), combining with a squeezed reservoir. Using experimentally realistic parameters for the MNP-QD architecture and fully quantized approach, we theoretically explore the optical properties of the hybrid molecule driven by an external applied laser field via probing the resonance fluorescence in the steady state. We show that in this way it is possible to engineer and control the peak-value magnitudes, widths, and shapes of the resonance fluorescence spectra under the influence of the squeezed vacuum field without the need for the strong-coupling condition between the MNP and QD. In particular, some interesting phenomena in rich spectral responses are attainable, including Fano-type resonance fluorescence, fluorescence quenching, fluorescence narrowing, and fluorescence enhancement. Our method can also be extended to other nanoscopic structures, such as a plasmonic nanoantenna coupled to an emitter. These unique line shapes obtained here may have potential applications in developing quantum plasmonic platforms and sensitive on-chip devices such as optical switches and sensors.

Effect of the nearby levels on the resonance fluorescence spectrum of the atom–field interaction

We study the resonance fluorescence in the Jaynes-Cummings model when nearby levels are taking into account. We show that the Stark shift produced by such levels generates a displacement of the peaks of the resonance fluorescence due to an induced effective detuning and also induces an asymmetry. Specific results are presented assuming a coherent and a thermal fields.

Bridging between laboratory and rotating-frame master equations for open quantum systems

The problem of a driven quantum system coupled to a bath and coherently driven is usually treated using either of two approaches: Employing the common secular approximation in the lab frame (as usually done in the context of atomic physics) or in the rotating frame (prevailing in, e.g., the treatment of solid-state qubits). These approaches are applicable in different parts of the parameter space and yield different results. We show how to bridge between these two approaches by working in the rotating frame without employing the secular approximation with respect to the driving amplitude. This allows us to uncover novel behaviors in regimes which were previously inaccessible or inaccurately treated. New features such as the qualitative different evolution of the coherence, population inversion at a lower driving amplitude, and novel structure in the resonance fluorescence spectrum of the system are found. We argue that this generalized approach is essential for analyzing hybrid systems, with components that come from distinctly different regimes which can now be treated simultaneously, giving specific examples from recent experiments on quantum dots coupled to optical cavities, and single-spin electron paramagnetic resonance.

Field-induced superposition effects on atom localization via resonance fluorescence spectrum

A driven two-level atomic system is exhaustively studied to explore the field-induced superposition effects in atom localization via resonance fluorescence spectroscopy. To this end, different field arrangements are incorporated as a combination of spatially aligned standing wave fields and traveling-wave field. Different localization patterns evolve with the variation in the resolution of localization for various parameter conditions. Particularly, multi-peak structures with the scope of decreasing localization peaks in one-dimension (1D) localization schemes both for sub-wavelength and sub-half-wavelength domains are interesting outcomes of sophisticated manipulation of field arrangements. Similar features are obtained for the two-dimension (2D) localization via suitable adjustment of control parameters. For both cases the strong impact of the traveling-wave field is noticeable as a controlling knob of localization behavior aiming at precision enhancement in position measurement of the single atom. The impact of discrete Lorentzians are also analyzed with a comparison of results obtained on the basis of exact analytic formalism as framed for the computation of resonance fluorescence spectrum. The proposed field configuration may be found suitable for application in the study of atom localization in an optical lattice arrangement.

Resonance fluorescence and quantum correlation of two-dimensional parabolic quantum dots: spin–orbit interaction effects

In the present study, we theoretically study the resonance fluorescence of a two-dimensional quantum dot with parabolic confinement under the effect of Rashba spin–orbit interaction and the magnetic field. We investigate the dependence of the resonance fluorescence and second-order correlation function on the strength of Rashba spin–orbit interaction and the magnetic field has. According to the numerical analyses conducted in this work, location and width of the peaks in the spectrum, as well as the second-order correlation function are modified by the Rashba spin–orbit interaction. In addition, our results show that the presence of magnetic field leads to the strong modification of both the resonance fluorescence spectrum and the second-order correlation function. Overall Rashba spin–orbit interaction and magnetic field can be used for the arbitrary control of the resonance fluorescence characteristics in a quantum dot.

Controlling the emission and absorption spectrum of a quantum emitter in a dynamic environment

We study the emission spectrum and absorption spectrum of a quantum emitter when it is driven by various pulse sequences. We consider the Uhrig sequence of nonequidistant πx pulses, the periodic sequence of πxπy pulses and the periodic sequence of πz pulses (phase kicks). We find that, similar to the periodic sequence of πx pulses, the Uhrig sequence of πx pulses has emission and absorption that are, with small variations, analogous to those of the resonance fluorescence spectrum. In addition, while the periodic sequence of πz pulses produces a spectrum that is dependent on the detuning between the emitter and the pulse carrier frequency, the Uhrig sequence of nonequidistant πx pulses and the periodic sequence of πxπy pulses have spectra with little dependence on the detuning as long as it stays moderate along with the number of pulses. This implies that they can also, similar to the previously studied periodic sequence of πx pulses, be used to tune the emission or absorption of quantum emitters to specific frequencies, to mitigate inhomogeneous broadening and to enhance the production of indistinguishable photons from emitters in the solid state.

Controllable radiation properties of a driven exciton-biexciton quantum dot couples to a graphene sheet

We investigate the radiation properties of a driven exciton-biexciton structure quantum dot placed close to a graphene sheet. The study of the Purcell factor then demonstrates the tunability of light-matter coupling, which in turn provides the possibility to control the steady-state populations. As the result, dipole transitions can be selectively enhanced and asymmetry in the resonance fluorescence can be observed. Meanwhile, both quadratures can exhibit two-mode squeezing at the Rabi sideband frequencies. A further study shows that although the increase in the environment temperature has a destructive influence on the population imbalance, squeezing occurs even at room temperature. Due to the flexibility in controlling the resonance fluorescence spectrum and producing two-mode squeezed states, our proposal would have potential applications in quantum information and other quantum research fields.

Third-order frequency-resolved photon correlations in resonance fluorescence

Recently, the concept of an ''$N$-photon spectrum'' -- a spectrally resolved $N$-photon correlation function -- has been introduced as an innovative quantum optics characterization tool that uniquely reveals information about pathways underlying the generation of light in a given source. Here, the authors investigate experimentally the three-photon spectrum of resonance fluorescence from a single semiconductor quantum dot. The observations agree with previous theoretical work, revealing significantly more pronounced photon antibunching at the Mollow triplet sidebands and more strongly correlated emission through virtual states compared to the two-photon counterpart.

Phase control of asymmetrical Mollow sideband in a Δ-type superconducting artificial atom

Abstract We investigate the resonance fluorescence spectrum (RFS) from a three-level Δ -configuration artificial atom, which is realized using superconducting quantum circuits (SQCs). There exists a cyclic transition structure due to the broken mirror symmetry, in which three microwave fields are simultaneously applied to drive the corresponding atomic transitions. We find that the microwave fluorescence photons can be emitted on exact one-, two- and three-photon resonance conditions. This is different from natural atom, in which the fluorescence is completely quenched due to dark-state resonance. More interestingly, it is noted that the suppression or enhancement of red (blue) sideband can be controlled by the relative phase of the applied microwave fields. The internal mechanism can be understood based on dressed-state analysis. The phase-sensitive RFS from solid-state devices may find potential application in designing all-optical switch and quantum information processing.

Theory of non-Markovian dynamics in resonance fluorescence spectrum

We present a detailed theoretical study of non-Markovian dynamics in the fluorescence spectrum of a driven semiconductor quantum dot (QD), embedded in a cavity and coupled to a three-dimensional (3D) acoustic phonon reservoir. In particular, we investigate the effect of pure dephasing on one of the side-peaks of the Mollow-triplet spectrum, expressed in terms of the off-diagonal element of the reduced system operator. The QD is modeled as a two-level system with an excited state representing a single exciton, and ground state represents the absence of an exciton. Coupling to the radiative modes of the cavity is treated within usual Born-Markov approximation, whereas dot-phonon coupling is discussed within non-Markovian regime beyond Born approximation. Using an equation-of-motion technique, the dot-phonon coupling is solved exactly and found that the exact result coincides with that of obtained within Born approximation. Furthermore, a Markov approximation is carried out with respect to the phonon interaction and compared with the non- Markovian lineshape for different values of the phonon bath temperature. We have found that coupling to the phonons vanishes for a resonant pump laser. For a non-resonant pump, we have characterzied the effect of dot-laser detuning and temperature of the phonon bath on the lineshape. The sideband undergoes a distinct narrowing and aquires an asymmetric shape with increasing phonon bath temperature. We have explained this behavior using a dressed-state picture of the QD levels.

Spectral asymmetries in the resonance fluorescence of two-level systems under pulsed excitation.

We present an open-system master equation study of the coherent and incoherent resonance fluorescence spectrum from a two-level quantum system under coherent pulsed excitation. Several pronounced features that differ from the fluorescence under a constant drive are highlighted, including a multi-peak structure and a pronounced off-resonant spectral asymmetry, in stark contrast to the conventional symmetrical Mollow triplet. We also study semiconductor quantum dot systems using a polaron master equation and show how the key features of dynamic resonance fluorescence change with electron-acoustic-phonon coupling.

Targeting intracellular MMPs efficiently inhibits tumor metastasis and angiogenesis.

Treatment for metastatic cancer is a great challenge throughout the world. Commonly, directed inhibition of extracellular matrix metalloproteinases (MMPs) secreted by cancer cells can reduce metastasis. Here, a novel nanoplatform (HPMC NPs) assembled from hyaluronic acid (HA)-paclitaxel (PTX) prodrug and marimastat (MATT)/β-casein (CN) complexes was established to cure a 4T1 metastatic cancer model via targeting CD44 and intracellular, rather than extracellular, MMPs.Methods: HPMC NPs were prepared by assembling the complexes and prodrug under ultrasonic treatment, which the interaction between them was evaluated by förster resonance energy transfer, circular dichroism and fluorescence spectra. The developed nanoplatform was characterized via dynamic light scattering and transmission electron microscopy, and was evaluated in terms of MMP-sensitive release and stability. Subsequently, the cellular uptake, trafficking, and in vitro invasion were studied by flow cytometry, confocal laser microscopy and transwell assay. MMP expression and activity was determined by western blotting and gelatin zymography. Finally, the studies of biodistribution and antitumor efficacy in vivo were performed in a mouse 4T1 tumor breast model, followed by in vivo safety study in normal mouse.Results: The interaction between the prodrug and complexes is strong with a high affinity, resulting in the assembly of these two components into hybrid nanoparticles (250 nm). Compared with extracellular incubation with MATT, HPMC NP treatment markedly reduced the expression (100%) and activity (50%) of MMPs in 4T1 cells and in the tumor. HPMC NPs exhibited 1.4-fold tumor accumulation, inhibited tumor-growth by >8-fold in volume with efficient apoptosis and proliferation, and suppressed metastasis (>5-fold) and angiogenesis (>3-fold). Overall, HPMC NPs were efficient in metastatic cancer therapy. Conclusions: According to the assembly of polymer prodrug and protein-drug complexes, this study offers a new strategy for constructing nanoparticles for targeted drug delivery, biomedical imaging, and combinatorial treatment. Importantly, via inhibition of intracellular MMPs, metastasis and angiogenesis can be potently blocked, benefiting the rational design of nanomedicine for cancer treatment.

Absorption and emission properties of QD-like particles

In this work we present a theoretical calculation of the absorption spectra of a weak probe signal and the resonance fluorescence spectra of two-level systems with a cw excitation with phonon-induced transitions.

Terahertz resonance fluorescence and squeezing in quantum dots: Effects of external electric field and dimension

The resonance fluorescence and phase-dependent spectrum in a typical quantum dot under the influence of an external electric field with attention to intersubband transitions driven by a laser field is studied. Finding energy eigenvalues and functions of the system, optical transition rates and Rabi frequency are calculated and effects of an external electric field and quantum dimension on the resonance fluorescence, squeezing and population of energy levels are investigated. Results show the fluorescence characteristics in Terahertz region of electromagnetic radiation strongly depend on external field and quantum dot dimensions. It is possible to control the resonance fluorescence and related phenomena via external factors and precise engineering of the system.

Mirror-assisted coherent backscattering from the Mollow sidebands

In front of a mirror, the radiation of weakly driven large disordered clouds presents an interference fringe in the backward direction, on top of an incoherent background. Although strongly driven atoms usually present little coherent scattering, we here show that the mirror-assisted version can produce high contrast fringes, for arbitrarily high saturation parameters. The contrast of the fringes oscillates with the Rabi frequency of the atomic transition and the distance between the mirror and the atoms, due to the coherent interference between the carrier and the Mollow sidebands of the saturated resonant fluorescence spectrum emitted by the atoms. The setup thus represents a powerful platform to study the spectral properties of ensembles of correlated scatterers.

Efficiently tunable photon emission from an optically driven artificial molecule

In this work, the emission properties of double quantum dots driven by an intense monochromatic electromagnetic field, while undergoing resonant tunnelling, are investigated. We find the optically active energy transitions and their corresponding emission intensity, and compute resonance fluorescence spectra for different detunings between the direct and indirect exciton energies. The simulated emission exhibit either three, five, or seven peaks, tunable on demand. On the basis of the obtained results, our proposal offers efficient control of the resonance fluorescence of an artificial molecule, suitable for optoelectronic applications.

Resonance fluorescence and phase-dependent spectra of a singly charged n -doped quantum dot in the Voigt geometry

We report on the resonance fluorescence and phase-dependent spectra in singly charged $n$-doped quantum dots in the presence of a strong external magnetic field in the Voigt geometry. The use of a nonresonant laser field driving two of the four active transitions results in the obtention of fluorescent photons along the four channels. The fluorescent photons coming from the two undriven transitions exhibit sidebands whose spectral location can be tuned through the Rabi frequency of the driving field and, most interestingly, their linewidths remain subnatural even for large values of the Rabi frequency of the laser field. It is shown that those sidebands present quantum fluctuations below the fundamental limit set by vacuum fluctuations. The numerical findings are fully explained by considering how the dressed states evolve in terms of the external physical magnitudes: the detuning, the Rabi frequency, and the dephasing rates.

Algorithm for solving the inverse vibronic problem on the basis of SVL fluorescence spectra

Computer methods whereby the inverse vibronic problem is solved on the basis of resonance fluorescence spectra with the use of modern quantum-mechanical methods for constructing structuraldynamic models of polyatomic molecules are discussed. An algorithm is proposed for solving the inverse vibronic problem according to resonance fluorescence spectra under laser excitation, and the corresponding calculation programs are constructed. The initial program data are acquired by means of an original software package which implements the scaling of quantum-mechanical force fields in two electronic states. The Duschinsky matrix and the initial matrix of shifts in normal coordinates caused by electron excitation are calculated in the Cartesian and natural vibrational coordinates. The program data are taken from quantum-molecular models based on calculations performed via ab initio modern quantum-mechanical methods and density functional theory. The algorithm is tested through the calculation of a model molecular system.

Control of resonance fluorescence of a four-level quantum emitter near a plasmonic nanostructure

We present a theoretical study of the resonance fluorescence of a four-level double-$\mathsf{V}$-type quantum emitter near a plasmonic nanostructure. The quantum system interacts with two orthogonal circularly polarized laser fields with the same frequency and intensity, but with different phases. For the plasmonic nanostructure we consider a two-dimensional array of metal-coated dielectric nanospheres. We show that the presence of the plasmonic nanostructure leads to strong modification of both the resonance fluorescence spectrum and the transition from antibunching to bunching for the fluorescent photons. In addition, we show that both the resonance fluorescence spectrum and the second-order correlation function are strongly phase-dependent so that the relative phase of laser fields can be used for the efficient control of the resonance fluorescence characteristics. The results are explained by using a dressed-state picture.

On algorithms for calculating the SVL-fluorescence spectra of polyatomic molecules

A software package for modeling the fluorescence spectra from a single vibrational level (SVL) of excited electron states under resonance laser excitation, in the adiabatic approximation with allowance for the “confusion” of normal coordinates under electron excitation, i.e., the Dushinsky effect, is presented. To algorithmize the calculation of the intensities in resonance fluorescence spectra, thirteen modules for the calculating Franck–Condon integrals are created. To optimize the calculation process, some simpler expressions are derived for the common terms of nested sums in the formulas for calculating Franck–Condon integrals from tone and overtone levels. To accelerate calculations, some constraints in the form of inequalities are additionally imposed on the range of vibrational quantum numbers in the ground electron state. The proposed algorithm for the modeling of SVL-fluorescence spectra of polyatomic molecules is based on quantum models of molecules in the ground and excited electron states calculated within the framework of contemporary ab initio quantum-mechanical methods and methods based on density functional theory.