Three-level Quantum Dot Research Articles

Optical response properties of a hybrid optomechanical system with quantum dot molecules assisted by second-order optomechanical coupling

We theoretically investigated the optical response properties of the optical field in three-level quantum dot molecules assisted optomechanical system consisting of the mechanical resonator. We show that various system parameters like second-order optomechanical coupling can control these nonlinear effects. In this work, we study how the system parameters affect the normal mode splitting of the movable mirror and output field. Further, we show that the second-order optomechanical coupling plays an important role in creating optomechanical entanglement as well as producing a strong squeezing spectrum of the optical field.

Controlled unidirectional reflectionlessness by coupling strength in a non-Hermitian waveguide quantum electrodynamics system

Unidirectional reflectionlessness is investigated in a waveguide quantum electrodynamics system that consists of a cavity and a [Formula: see text]-type three-level quantum dot coupled to a one-dimensional plasmonic waveguide. Analytical expressions of transmission and reflection coefficients are derived and discussed for both resonant and off-resonant couplings. By appropriately modulating the coupling strength, phase shift and Rabi frequency, unidirectional reflectionlessness is observed at the exceptional points (EPs). And unidirectional coherent perfect absorption is exhibited at the vicinity of the EP. These results might find applications in designing quantum devices of photons, such as optical switches and single-photon transistors.

Electromagnetically induced grating in azimuthal dependent three-level quantum dot system

The Fraunhofer diffraction pattern in a three-level quantum dot nanostructure is examined. A probe light, a two-dimensional standing wave field, and a weak signal light are the three optical laser fields that the graphene quantum dot interacts with them. The Fraunhofer diffraction pattern of the probe transmitted light has been addressed under two different coupling situations, including when the weak signal light into an optical vortex beam and a plane wave. The Fraunhofer diffraction pattern becomes symmetric for plane wave coupling light, and the diffracted light can be adjusted by the relative phase between applied lights. However, using the orbital angular momentum of light, it is possible to obtain an asymmetric diffraction pattern for optical light. It has been discovered that in both instances, phase modulation of the probe light’s transmission function allows the probe energy to move from zero order to higher orders.

Incoherent control of Goos–Hänchen shifts in a tunneling quantum dot molecule

In this letter, we propose a novel model for adjusting the Goos–Hänchen shifts (GH) from a fixed cavity. A three-level double quantum dot (QD) molecule is doped in the cavity, which interacts with a probe laser field and an incoherent pumping rate. We initially investigate the refraction index of double QDs utilizing the quantum mechanical density matrix approach in order to achieve negative and positive refractive indexes. The GH shifts of reflected and transmitted light beams in positive and negative refraction indices of the intracavity medium were then studied. The improved negative or positive GH shifts in reflected and transmitted light beams may be accomplished by changing the incoherent pumping rate and tunneling effect. Our findings reveal that the magnitude of the GH shifts is greatly influenced by the absorption of incoming probing light in double QDs. The enormous GH shifts for the perfect tuning cavity have been seen at a given incidence angle.

Quantum coherence-assisted optical properties and drag of SPPs on quantum dots and resonantly-coupled dots-metal plasmonic interfaces via interbands tunneling and Fano resonance

Owing to their peculiar properties of great fundamental and practical implications, surface plasmons and exciton-plasmons interaction have attracted immense interest in the recent decades. In this regard, quantum dots and dots-metal waveguides and interfaces are promising candidates. In this article, we report first theoretical demonstration on the detailed optical and optotransport properties and surface plasmon polaritons (SPPs) dragging via quantum dots interbands tunneling-induced quantum coherence. For the required properties of SPPs, we proposed a resonantly coupled dots-metal plasmonic interface, which comprises of ensemble of three-level double quantum dot molecules (DQDMs) placed on the flat surface of gold thin film. For the theoretical results, we first solved analytically the density-matrix equation for the eigenvalues of the DQDMs in the Λ− type configuration. In view of the dressed-states picture, we interpreted the results further with regard to EIT (electromagnetically induced transparency), PIT (plasmonic induced transparency) and Fano interference. In particular, we elaborate on the role of interplay of the quantum dots and the coupled plasmonic resonances on the optical, optical-cum transport properties and drag of SPPs. We predict ultrafast superluminal group velocity for SPPs of the order 1.5×1010 m/s, quality factor of 38.48, confinment factor 1.52 and the optimum drag for SPPs of order 0.2 micro meter/radian.

Cooling of micromechanical oscillator in a hybrid optomechanical system with three-level quantum dots

We propose a ground state cooling scheme for an optomechanical resonator based on the system of a V-type three-level QD ensemble trapped in a two-mode cavity. The two-mode cavity was pumped by two different deriving fields. We studied the optomechanical cooling under the highly unresolved-sideband and beyond Lamb-Dicke regime (coupling strength between the cavity field and the phonon field not far less than the vibrational frequency). Our results show that the noise spectrum appeared a single peak when the detuning of the QD’s high excitation state and high-frequency driving field equals that of the QD’s low excitation state and low-frequency driving field, otherwise, then appeared double peaks. In the case of double peaks, we can realize the transition between optomechanical cooling and heating by changing the coupling strength of QD with cavity field, which is not available in the case of a single peak. We also studied the evolution of the mean phonon number with time, which is helpful to analyze ground state optomechanical cooling.

Active controlled dual-band unidirectional reflectionlessness by classical driving field in non-Hermitian quantum system

We propose a scheme to realize the active controlled dual-band unidirectional reflectionlessness at exceptional points by classical driving field in a non-Hermitian quantum system that consists of two Λ-type three-level quantum dots side coupled to a plasmonic waveguide. We demonstrate that the dual-band unidirectional reflectionlessness can be controlled by appropriately tuning classical driving field, phase shift between two quantum dots, dissipations of two quantum dots, and quantum dot-waveguide coupling strengths. Furthermore, the dual-band unidirectional reflectionlessness spectra with quality factors of ∼375.40 and ∼402.59 can be obtained in the forward and backward directions, respectively.

Information entropy and population inversion of a three-level semiconductor quantum dot

In this paper, an analytical solution for a three-level semiconductor quantum dot has been presented. From this solution, we have discussed the effects of the phenomenological damping parameters, the electromagnetic field amplitude $$E_{0}$$ of the excitation pulse $$E(\omega )$$ , and the detuning parameters on the atomic occupation probabilities, the atomic population inversion, the purity, and the information entropy $$H(\sigma _\mathrm{{z}}). $$ A long-lived quantum coherence obviously has emerged in all figures. Besides, a decay has appeared in all curves of the atomic occupation probability $$\rho _{gg}(t),$$ the atomic population inversion, and the purity. Since there are not sufficient mathematical solutions for such systems, our study may add further insight into many dynamic systems, and this in turn should open up a wide range of applications for semiconductor quantum dot.

A single plasmon router based on the V-type three-level quantum dot sandwiched between two plasmonic waveguides

A single photon router with a desired high routing rate is of great importance for quantum networks. Recently, coupling between channeled plasmons and quantum emitters have been widely used to explore the routing feasibility in hybrid systems. As a capable alternative, we suggested a scheme of a single plasmon router using a V-type three-level quantum dot (QD) sandwiched between two plasmonic waveguides. We theoretically investigated the transmission and transfer rates of single plasmons in the complex system via the real-space approach. Our calculations show that the single plasmons from the incident route could be redirected by controlling such parameters as the intensity of the classical field, the detunings and the couplings between the QD and the plasmonic waveguides. Our proposed scheme could be used not only for the design of a single plasmon router but also for the design of quantum switches and quantum couplers in quantum photonic integrated circuits.

Renormalization group transport theory for open quantum systems: Charge fluctuations in multilevel quantum dots in and out of equilibrium

We present the real-time renormalization group (RTRG) method as a method to describe the stationary state current through generic multi-level quantum dots with a complex setup in nonequilibrium. The employed approach consists of a very rudiment approximation for the RG equations which neglects all vertex corrections while it provides a means to compute the effective dot Liouvillian self-consistently. Being based on a weak-coupling expansion in the tunneling between dot and reservoirs, the RTRG approach turns out to reliably describe charge fluctuations in and out of equilibrium for arbitrary coupling strength, even at zero temperature. We confirm this in the linear response regime with a benchmark against highly-accurate numerically renormalization group data in the exemplary case of three-level quantum dots. For small to intermediate bias voltages and weak Coulomb interactions, we find an excellent agreement between RTRG and functional renormalization group data, which can be expected to be accurate in this regime. As a consequence, we advertise the presented RTRG approach as an efficient and versatile tool to describe charge fluctuations theoretically in quantum dot systems.

Control of electromagnetically induced transparency via a hybrid semiconductor quantum dot–vanadium dioxide nanoparticle system

We numerically investigate the electromagnetically induced transparency (EIT) of a hybrid system consisting of a three-level quantum dot (QD) in the vicinity of vanadium dioxide nanoparticle (VO2NP). VO2NP has semiconductor and metallic phases where the transition between the two phases occurs around a critical temperature. When the QD-VO2NP hybrid system interacts with continuous wave laser fields in an infrared regime, it supports a coherent coupling of exciton–polariton and exciton–plasmon polariton in semiconductor and metal phases of VO2NP, respectively. In our calculations a filling fraction factor controls the VO2NP phase transition. A probe and control laser field configuration is studied for the hybrid system to measure the absorption of QD through the filling fraction factor manipulations. We show that for the VO2NP semiconductor phase and proper geometrical configuration, the absorption spectrum profile of the QD represents an EIT with two peaks and a clear minimum. These two peaks merge to one through the VO2NP phase transition to metal. We also show that the absorption spectrum profile is modified by different orientations of the laser fields with the axis of the QD-VO2NP hybrid system. The innovation in comparison to other research in the field is that robust variation in the absorption profile through EIT is due to the phase transition in VO2NP without any structural change in the QD-VO2NP hybrid system. Our results can be employed to design nanothermal sensors, optical nanoswitches, and energy transfer devices.

Efficient purification and concentration for $$\varLambda $$ Λ -type three-level entangled quantum dots using non-reciprocal microresonators

Distribution of maximal entanglement is a key technique in long-distance quantum communication. In particular, the entanglement distribution with high fidelity relies on the efficient entanglement purification and concentration. Here in this study, we present a feasible approach to complete the entanglement purification and entanglement concentration for $$\varLambda $$ -type three-level entangled quantum dots by using the whispering-gallery-mode microcavity and the quantum dot coupled system. Exploiting the input–output process of the probe light, we design a parity check gate which allows the quantum non-demolition measurement on the remote entangled quantum dots. Moreover, one can distill a high-fidelity entangled solid-state ensemble from a mixed entangled state or less entangled state ensemble non-locally. The proposed protocol exhibits the advantages of high fidelity which could be further applied to quantum repeaters and quantum information processing with the current experimental technologies.

Plasmonic Effect on the Optical Properties in a Hybrid V-Type Three-Level Quantum Dot-Metallic Nanoparticle Nanosystem

We investigated theoretically the exciton–plasmon coupling effects on the population dynamics and the absorption properties of a hybrid nanosystem composed of a metal nanoparticle (MNP) and a V-type three-level semiconductor quantum dot (SQD), which are created by the interaction with the induced dipole moments in the SQD and the MNP, respectively. Excitons of the SQD and the plasmons of the MNP in such a hybrid nanosystem could be coupled strongly or weakly to demonstrate novel properties of the hybrid system. We also find that the gain happens in such a hybrid system, because of the coherent interaction between the SQD and the MNP. Our results show that the non-linear optical response of the hybrid nanosystem can be greatly enhanced or depressed due to the exciton–plasmon couplings.

Photoelectric converters with quantum coherence.

Photon impingement is capable of liberating electrons in electronic devices and driving the electron flux from the lower chemical potential to higher chemical potential. Previous studies hinted that the thermodynamic efficiency of a nanosized photoelectric converter at maximum power is bounded by the Curzon-Ahlborn efficiency η_{CA}. In this study, we apply quantum effects to design a photoelectric converter based on a three-level quantum dot (QD) interacting with fermionic baths and photons. We show that, by adopting a pair of suitable degenerate states, quantum coherences induced by the couplings of QDs to sunlight and fermion baths can coexist steadily in nanoelectronic systems. Our analysis indicates that the efficiency at maximum power is no longer limited to η_{CA} through manipulation of carefully controlled quantum coherences.

Design of all-optical memory cell using EIT and lasing without inversion phenomena in optical micro ring resonators

The proposed design of the optical memory unit cell contains dual micro ring resonators in which the effect of lasing without inversion (LWI) in three-level nano particles doped over the optical resonators or integrators as the gain segment is used for loss compensation. Also, an on/off phase shifter based on electromagnetically induced transparency (EIT) in three-level quantum dots (QDs) has been used for data reading at requested time. Device minimizing for integrated purposes and high speed data storage are the main advantages of the optical integrator based memory.

Scattering of a Single Plasmon by Two-Level and V-Type Three-Level Quantum Dot Systems Coupled to 1D Waveguide

We theoretically investigated the transmission properties of a single plasmon interacting with two-level quantum dots (QDs) and a V-type three-level QD, coupled to plasmonic waveguide, respectively. We investigated the transmission of a single plasmon by a system including a V-type three-level QD and compared it with that by a system including only two-level QDs.

Switching of a Single Photon by Two Λ-Type Three-Level Quantum Dots Embedded in Cavities Coupling to One-Dimensional Waveguide

Switching of a single photon interacting with two {\Lambda}-type three-level quantum dots embedded in cavities coupled to one-dimensional waveguide is investigated theoretically via the real-space approach. We demonstrated that switching of a single photon can be achieved by tuning the classic driving field on or off, and by controlling the QD-cavity coupling strength, Rabi frequency and the cavity-waveguide coupling rate. The transmission properties of a single photon by such a nanosystem discussed here could find the applications in the design of next-generation quantum devices and quantum information.

Spatial weak-light ring soliton in self-assembled quantum dots

By using semiclassical theory combined with multiple-scale method, we analytically study the linear absorption and the nonlinear dynamical properties in a lifetime broadened Λ-type three-level self-assembled quantum dots. It is found that this system can exhibit the transparency, and the width of the transparency window becomes wider with the increase of control light field. Interestingly, a weak probe light beam can form spatial weak-light dark solitons. When it propagates along the axial direction, the soliton will transform into a steady spatial weak-light ring dark soltion. In addition, the stability of two-dimensional spatial optical solitons is testified numerically.

Controlling single-photon transport with three-level quantum dots in photonic crystals

We investigate how to control single-photon transport along the photonic crystal waveguide with the recent experimentally demonstrated artificial atoms [i.e., $\ensuremath{\Lambda}$-type quantum dots (QDs)] [S. G. Carter et al., Nat. Photon. 7, 329 (2013)] in an all-optical way. Adopting full quantum theory in real space, we analytically calculate the transport coefficients of single photons scattered by a $\ensuremath{\Lambda}$-type QD embedded in single- and two-mode photonic crystal cavities (PCCs), respectively. Our numerical results clearly show that the photonic transmission properties can be exactly manipulated by adjusting the coupling strengths of waveguide-cavity and QD-cavity interactions. Specifically, for the PCC with two degenerate orthogonal polarization modes coupled to a $\ensuremath{\Lambda}$-type QD with two degenerate ground states, we find that the photonic transmission spectra show three Rabi-splitting dips and the present system could serve as single-photon polarization beam splitters. The feasibility of our proposal with the current photonic crystal technique is also discussed.

Theory of four-wave mixing in quantum dot semiconductor optical amplifiers

The theory of four-wave mixing (FWM) in quantum dot (QD) semiconductor optical amplifiers (SOAs) has been discussed by the combination of the QD rate equations system and the pulse propagation in QD SOAs. This study has covered two types of QD structures: the two-level QD structure, where the ground state (GS) and wetting layer have been considered; and the three-level QD structure, where the excited state (ES) has been taken into account. The relations for differential gain were also discussed. FWM efficiency and its components, comprising spectral hole burning, carrier heating and carrier density pulsation (CDP), are calculated.The results show that inclusion of ES is essential. At a high carrier density and for a long term frequency, the FWM was found to be detuning independently while it is symmetric for short pulses. Neglecting CH makes the FWM in QD SOAs symmetric and detuning independent, which are desired characteristics for optical communication applications. The results corroborate available experimental observations. The effective capture time of QD is the main parameter and can be ascribed to the differences between the two- and three-level models.