Role of intense laser-excited dressed states via electromagnetically induced transparency on the Fresnel-Fizeau photon drag through an asymmetric double quantum dot molecule (GaAs/AlGaAs) in the -type configuration
Introduction
Inspired by Fresnel's drag theory [[1], [2], [3]], considerable efforts have been carried out to demonstrate the phenomenon of light drag using various schemes on dielectric media [[4], [5], [6], [7], [8], [9], [10], [11]]. Arnold et al. [12] reported a considerable enhancement in the rotary photon drag in a slow-light spinning ruby medium. Carusotto et al. [13] reported transverse light drag in a strongly dispersive slow-moving media via electromagnetically induced transparency (EIT), a well-known phenomenon of quantum coherence. Kuan et al. [14] reported experimental observations on light drag enhancement by at least 3 orders of magnitude as compared to the value measured in earlier experiments, via EIT in a three-level cold Rb-85 atomic medium. Safari et al. [15] reported experimental measurement on the longitudinal light drag in rubidium vapors. Recently, Kazemi and Mahmoudi [16] reported a considerable photon-drag enhancement in a three-level -type non-chiral and chiral medium, with different predictions of photon drag for right- and left-handed chiral schemes. Earlier, the author with collaborators investigated gain-assisted-superluminal rotary drag of photon and surface plasmon polariton (SPP) using N-type four-level atomic medium alone and the collective metallic-atomic interface, respectively [17]. Consequently, the authors studied EIT-assisted lateral photon-drag enhancement in a five-level slow-moving atomic medium [18]. Rafi et al. [19] reported an unusual refraction and Fizeau rotary dragging effect in a chiral media using linearly polarized pulse. More recently, Solomongs [20] and collaborators reported transverse light drag enhancement by a factor in a slow-light EIT medium. More recently, the author and collaborators [21] reported gain-assisted-superluminal photon drag in an invert-N-type four-level atomic medium with positive and negative refractive indices.
The growing interest on light drag and superluminal propagation owes to many-fold fundamental and practical implications of the concept in the fields of atomic and molecular physics, condensed matter physics, nanophotonics, quantum optics, nanoplasmonics and nanoelectronics. By implementing the basic concepts of light-matter interaction, the novel nanophotonic and optoelectronic devices may lead to low-loss data and high-speed image transmission. Besides, light drag finds applications in enhancing the measuring accuracy of devices [22,23], massive particles drag [24,25], dielectric analogies [26], and invisible clocking [27,28]. The physical origin of light drag stems from the rotation of light linear polarization state subjected to the parallel or perpendicular motion of the medium. The polarization rotation, on the other hand, finds innovative technological implications such as in image coding [12], optical switches and logic gates [[29], [30], [31]], efficient light modulation in photonic devices [32], plasmonics [33], and gyro-compass applications [34].
On the other hand, with the advent of novel experimental methods, we can form various structures of single quantum dots (QDs), coupled QDs molecules (CQDMs) and quantum-dot supercrystals by micro-fabrication; for example, via self-assembly either through epitaxial growth or chemical synthesis or scanning tunneling microscopy and spectroscopy [[35], [36], [37]]. This in turn enhanced considerably our understanding and practical realization on many fundamental phenomenon in the fields of condensed-matter physics, atomic and molecular physics, quantum optics, nanophotonics and nanoplasmonics. For instance, in contrast to routine atomic or atomic-metal interfaces, currently researchers are employing extensively the quantum dots, dots-metallic or dots-nanoparticle interfaces for the realization of the energy-efficient next-generation optoelectronic devices. In fact, in contrast to atomic media, single QDs and multi-structured CQDMs are potentially more promising with regard to flexibility in their structural and bandgap topology, enhanced charge confinement and atomic like energy levels induced by quantum tunneling. This offers a great opportunity to tune the physical properties of QDs and CQDMs by various methods such as quantum coherence via spontaneous emission, EIT, incoherent pumping and electron tunneling. This in turn may help to control and improve on the electronic and optical properties of the QD-based nanooptical and nanophotonic devices. This includes optical band gap engineering, improved electrical conductivity, enhanced light dispersion, reflection, transmission and absorption, more conveniently. Besides, as QDs systems can form confined artificial atoms or molecules with three dimension geometry so they are considered potential candidates as qubits in quantum computing and quantum information. For the coherent generation and manipulation in a double QD molecule (DQDM), the tunneling between the neighbouring QDs can be induced by exciting the electric gates. Earlier, three-level DQDMs with different geometry and parameters were exploited in various contexts. This include phase control of the group velocity [38], absorption-free superluminal propagation [39], photon drag [40] with incoherent pumping rate, the slow-light propagation [41], coherent control of electron tunneling [42], superluminal optical soliton [43] without incoherent pumping rate, EIT under intense non-resonant laser field subjected to magnetic and electric fields [[44], [45], [46]].
Mostly in the above-mentioned schemes of quantum dots, quantum coherence effects like EIT were accomplished via gate voltage-driven interdot tunneling. On the other hand, Bejan and Niculescu [[44], [45], [46]] employed non-resonant intense lasers to achieve the phenomenon of EIT for the theoretical manipulation of electronic and optical properties in view of quantum interference of the dressed states. While Kosionis [47] discussed the role of dressed states on four-wave mixing in an asymmetric three-level double quantum dot molecule. Sakiroglu et al. [48] and Kilic et al. [49] employed quantum pseudodot system subjected to intense laser field in the presence of magnetic field to investigate, respectively, the third-harmonic generation and optical response of the systems. Tiutiunnyk and collaborators [50] investigated optical properties of triangular-shape GaAs quantum dots with finite barrier confinement via intersubband electronic transitions. On the other hand, Sari and collaborators [51] reported theoretical investigation on the effects of non-resonant intense laser field on the donor impurity binding energy in a cylindrical quantum dot in the framework of the effective mass approximation.
However, to the best of our knowledge, no work has been reported on the role of intense laser-excited dressed sates via EIT on the superluminal-assisted propagation, optical properties and lateral/rotary photon drag in an asymmetric double quantum dot molecule GaAs/AlGaAs in the -type configuration, which is the main motivation of the current work. We are mainly concerned to look answers for some of the intriguing questions in this connection. For instance, as to how the application of intense laser field on the GaAs/AlGaAs DQDM could modify the structure of the system via quantum interference of the dressed states in view of EIT. To what extent this in turn, could modify the nature of light propagation, as to whether subluminal or superluminal, in view of the modification of medium susceptibility, i. e. the modification in light absorption and dispersion? Further, it is also of great interest to investigate as to how the laser-modified susceptibility of the medium in turn could tune the optical properties of the quantum dot medium to be interpreted in terms of probe field group index, group velocity, group delay, phase delay as well as lateral and rotary drag of photon. Before expanding on the detailed optical properties and lateral/rotary drag of photon in the proposed quantum dot scheme subjected to intense laser control field, we will apply compact density matrix theoretical framework to calculate analytically the required probe transition. In particular, we present the detailed analytical solution of the density matrix equations in the weak perturbation regime in order to obtain the eigenvalues of the system in view of the dressed states. Finally, besides interpreting the theoretical results in connection with the underlying physical picture and prospects for potential implications, we will also elaborate on the theoretical predictions of our proposed model regarding the superluminal and subluminal propagation, optical properties and photon drag with the aid of numerical simulations.
The rest of this paper is organized as follows: In section 2, we introduce the proposed quantum-dot model and present the theoretical formulism based on density-matrix approach to calculate the eigenvalues of the system, probe coherent term, susceptibility, group index, group velocity, group delay and phase delay time. To elaborate our theoretical results further, we expand on the numerical presentation and discussion in section 3. Section 4 concludes the article with a key note on the main findings and implications of the study.
Section snippets
The proposed quantum model and theory
The general energy-level configuration of the proposed quantum model comprising of an asymmetric three-level DQDM is shown in Fig. 1(a). The system may reveal, under certain experimental conditions, the possible three-level configurations namely, (lambda), (ladder or cascade) or type [[43], [44], [45], [46]]. The lower state is without excitation (exciton) while the upper levels and correspond to the dot excitonic states representing the conducting mode of the proposed
Results and discussion
In the numerical simulations, we employed the spectral parameters with decay rates , where , [[44], [45], [46]], quantum dot number density , the probe wavelength m, , length of the medium is 20 cm. We assumed the system is in the ground state initially, i. e., and (i, j = 0, 1, 2). When the control field is OFF and signal (probe field) is switched ON, the interband transition between the states is
Conclusions
In conclusion, in this research work the author first time reported theoretically the role of intense laser-excited dressed states on the gain-assisted superluminal propagation, optical properties, lateral and rotary photon drag in view of electromagnetically induced transparency. For this, using density-matrix formulism, a detailed analytical solution was presented for the asymmetric double quantum dot molecule GaAs/AlGaAs in the three-level type configuration. The role of obtained
Declaration of competing interest
The author declares that he has no known competing financial interests or personal conflict of interest that could have appeared to influence the work reported in this paper.
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