Three-level System Research Articles

Design of 1450-1500nm Bismuth-doped Fiber Laser

With the rapid development of information technology, people's demand for the transmission capacity of fiber optic communication networks is increasing. How to broaden the bandwidth of communication systems has become one of the key issues in the field of communication. Researchers have found that the operating bandwidth of amplifiers mainly limits the bandwidth of communication systems. Although multiple solutions have been proposed and implemented to address this issue, there are still many gaps in the design of full-band multi wavelength-related light sources. By studying the three-level system of bismuth ions, the rate equation and power transfer equation of a bismuth ion doped fiber laser are simulated, and the pump power threshold and output power are calculated. Using MATLAB for simulation experiments, the relationship between laser power and pump power, as well as their variation with propagation distance, were ultimately obtained. The simulation results show that under 830 pump lights, the pump light threshold power is 10W. After reaching the threshold power, the pump light power and laser power have a linear relationship, and as the propagation distance increases, the pump light power gradually decreases and the laser power gradually increases. The analysis shows that the power generated by the signal light in this band meets the theoretical standards, which verifies the correctness of the scheme.

Real-imaginary spectrum decomposition of the transparency spectra in microwave dressed Rydberg systems

To distinguish the contributions of electromagnetically induced transparency (EIT) and Autler-Townes splitting (ATS) in their applications in precision laser spectroscopy, we propose a real-imaginary spectrum decomposition method to investigate the transparency spectra in a four-level microwave (MW) dressed Rydberg system. We show that the opening transparency windows in the absorption spectra of probe field is a prominent character by EIT, EIT-ATS crossover, and ATS when the MW field is turned off and the intensity of the control field is adjusted. When the MW field is turned on and gradually increased, the EIT is destroyed and disappears. In addition, the most prominent characters that open a transparency window are the EIT-ATS crossover and the ATS. Then, if we further increase the intensity of the MW field, we find that the transparency windows open mainly due to the ATS. Compared to the previous considerations of this issue, which were limited to three-level systems, our four-level scheme reported here is useful for understanding the features of quantum interference in multilevel atomic systems, and has potential applications to study enhanced sensitivity, measurement spectroscopic, quantum processing, quantum communication, and transmission.

Design of Fiber Laser Based on Erbium-ion

Erbium ions (Er3+) exhibit good characteristics of fiber lasers in the 1500-1550 nm band, including three-level systems, high tilt efficiency, and large emission cross sections. This article focuses on studying the spectral characteristics of erbium ions, simulating the power propagation equation of erbium-doped ion fiber lasers, and calculating the pump power threshold and output power. The findings of the simulation indicate that the laser begins to produce 10 W of pump optical power. The laser power hits 34.38 W and the oblique power is determined to be 38.20% as soon as the pump power exceeds 100 W. Experimental results show that when pump light propagates forward, the forward propagation power of the pump light will weaken, the forward propagation power of the signal light will increase, the reverse propagation of the signal light will weaken and the reverse propagation of the pump light will Transmission will also weaken, with directional transmission remaining largely unchanged. This study carried out numerical simulations on the experimental parameters of the fiber laser doped with Er3+and finally obtained the output power of pump light and signal light under these conditions, providing better data support for the preparation of 1500-1550 nm fiber laser doped with erbium ion.

Research on Measuring High-Quality Economic Development in Beijing

This paper constructs a three-level evaluation index system for the high-quality development of Beijing's economy from six dimensions and measures the level of high-quality development of the economy from 2000 to 2019 by using entropy weight TOPSIS. The main conclusions are as follows: from the perspective of the comprehensive measurement level, the level of high-quality development of Beijing's economy is constantly improving, but there is still a certain gap from the optimal value; from 2000 to 2004, the growth rate of high-quality development of the economy was slower, with an average annual increase of less than 1%; from the perspective of the measurement level of the first-level indexes, the coordinated development is maintained at 0.17, the open development has seen a small decline, and the remaining four dimensions have an obvious upward trend in the remaining four dimensions.

Research on the Evaluation of the Efficiency of Beijing's High-Quality Economic Development

This paper constructs a three-level evaluation index system for the high-quality development of Beijing's economy from six dimensions and evaluates the efficiency of high-quality development of the economy from 2000 to 2019 by using the DEA model with non-expected outputs. The main conclusions are as follows: from the point of view of development efficiency, the comprehensive efficiency as a whole shows a first decline and then an increase, and there is little difference in scale efficiency, which is completely close to scale efficiency.

Waveform Optimization Control of an Active Neutral Point Clamped Three-Level Power Converter System

Currently, the escalating integration of renewable energy sources is causing a steady weakening of grid strength. When grid strength is weak, interactions between inverters or those between inverters and grid line impedance can provoke widespread oscillations in the power system. Additionally, the diverse DC voltage application characteristics of power converter systems (PCS) may lead to over-modulation, generating narrow pulse issues that further impact control of the midpoint potential balance. Existing dead-time elimination methods are highly susceptible to current polarity judgments, rendering them ineffective in practical use. PCS, due to inherent dead-time effects, midpoint potential imbalances in three-level topologies, and narrow pulses, can elevate low-order harmonic content in the output voltage, ultimately distorting grid-connected currents. This is particularly susceptible to causing resonance in weak grids. To enhance the output voltage waveform of PCS, this article introduces a comprehensive compensation control strategy that combines dead-time elimination, midpoint potential balance, and narrow pulse suppression, all based on an active neutral point clamped (ANPC) three-level topology. This strategy gives precedence to dead-time elimination and calculates the upper and lower limits of the zero-sequence available for midpoint potential balance while fully compensating for narrow pulses. By prioritizing dead-time elimination, followed by narrow pulse suppression and finally midpoint potential balance, this method decouples the coupling between these three factors. The effectiveness of the proposed method is validated through semi-physical simulations.

Land scale division and multifunctional evaluation for Fuping County, China, based on DEM-based watershed analysis.

Land is the spatial background and basic carrier of human survival and development. The study of land function evaluation at different scales can promote the harmonious coexistence of humans and nature. Taking Fuping County, Hebei Province, China, as an example, this study establishes the theoretical framework of county-level land scale division using a digital elevation model (DEM)-based watershed analysis method and establishes the theory and methodological system of land function evaluation from the perspective of the characteristic scale. The multifunctionality of the land was evaluated using the Carnegie-Ames-Stanford approach (CASA), the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model and comprehensive index evaluation. By using the methods of DEM-based watershed analysis, dominant factor differentiation and layer superposition, a three-level scale system of 'subwatershed scale-land chain scale-land segment scale' and a multifunctional multiscale evaluation index system containing 18 evaluation indices were established. The single-function and multifunction evaluation results of land at different scales were obtained by the comprehensive index method and Getis-Ord Gi* index method. The accuracy of land function evaluation results mainly depends on the selection of the measurement scale. The land measurement scale determined by DEM-based watershed analysis is close to the intrinsic scale of land function evaluation. The scale effect of land function in different temporal and spatial ranges is also evident and shows obvious spatial heterogeneity and difference. At larger scales, individual functions show synergistic effects.

Optical storage of circular airy beam in atomic vapor

Abstract The realization of quantum storage of spatial light field is of great significance to the construction of high-dimensional quantum repeater. In this paper, we experimentally realize the storage and retrieval of circular Airy beams (CABs) by using the Λ-type three-level energy system based on the electromagnetically induced transparency in a hot rubidium atomic vapor cell. The weak probe beam field is modulated with phase distribution of CABs by a spatial light modulator. We store the probe circular Airy beam (CAB) into the rubidium atomic vapor cell and retrieve it after the demanded delay. We quantitatively analyze the storage results and give corresponding theoretical explanations. Moreover, we investigate the autofocusing and self-healing effect of the retrieved CAB, which indicates that the properties and beam shape of CAB maintain well after storage. Our work will have potential applications in the storage of high-dimensional quantum information, and is also useful for improving the channel capacities of quantum internet.

Investigation of diffraction grating in three-level gain medium

This research investigates the modulation of diffraction intensity distributions in both one- and two-dimensional scenarios within a three-level atomic system. The study employs a partially coherent light beam as the probe field, engaging with the atomic medium. Additionally, a control field capable of generating a standing wave is introduced. Analysis reveals that various parameters, including spatial coherence, beam width, and mode index of the partially coherent light, exert influence on the diffraction intensity distribution. The presence of a microwave field in the three-level atom is also considered, impacting the diffraction intensity distribution. Remarkably, the study observes that altering parameters such as microwave field strength and beam width of the partially coherent light results in the maximum energy of the probe field being transferred to higher orders, concurrently minimizing the central intensity. This distinctive method allows for the manipulation of diffraction intensity distribution through external control parameters. The proposed theoretical framework for creating a diffraction grating presents a novel avenue for experiment.

The logical Path and Stage Tasks For The Construction of a Three-level Grading Evaluation System for Professional Construction: "Standard, Quality, and Excellence"

Currently, there are only a few vocational colleges in China that carry out professional grading evaluation. Therefore, for the introduction and reference of undergraduate college professional grading evaluation in the field of higher vocational education, analyzing the positive significance of conducting professional grading evaluation in the field of higher vocational education and providing cases of establishing professional grading evaluation can help promote the level of professional construction in vocational colleges. This article suggests that based on a comparative analysis of the current status and existing problems of the application of professional grading evaluation in internal and external higher education institutions in China, we should analyze the data collection requirements and system functional requirements of professional grading evaluation, develop a professional construction quality evaluation platform, and provide intelligent solutions for standardizing the evaluation operations of higher vocational education majors. A series of operable, executable, and referenceable grading evaluation documents should be constructed to ensure the smooth and effective implementation of professional grading evaluation work, improve the level of professional construction, and lay a solid foundation for the high-quality development of schools.

Vortex beam induced spatial modulation of quantum-optical effects in a coherent atomic medium

We have studied two-dimensional absorption, gain, and corresponding refractive index profiles in a ladder-type three-level atomic system interacting with three coherent fields. One is a weak probe field considered as a plane wave, while the other two are the control fields taken as two Laguerre–Gaussian doughnut beams. Position dependence of two vortex beams induces the spatially modulated coherence at the condition of resonance, which enables us to obtain space-dependent absorption, transparency, gain without inversion (GWI), and refractive index enhancement in the present scheme. The azimuthal modulation of coherence effects is attributed to the presence of optical angular momentum of the vortex beams. Under the influence of an additional travelling wave field with the presence of two vortex beams, the present model leads us to obtain an ultra-large enhancement of refractive index at the resonant detuning of the fields. This phenomenon makes the atom-field system to play the equivalent role of a high-refractive-index prism. The role of near dipole–dipole (NDD) interaction on the modulation of position-dependent coherence effects has also been investigated. It has been shown that, without any inclusion of the travelling wave field in the system, the phenomenon of resonant enhancement of refractive index may also occur in the presence of NDD effect. The new way of generating spatially controlled GWI and nonlinear refractive index enhancement is specific to the present model. This work seems to be useful for finding its applications in spatially modulated coherence controlled electromagnetically induced transparency-based quantum devices like quantum optical memory, switches, and quantum logic gates, where the refractive index switching phenomenon is a prerequisite.

Developing a geographical-meteorological indicator system and evaluating prediction models for alveolar echinococcosis in China.

Geographical and meteorological factors have been reported to influence the prevalence of echinococcosis, but there's a lack of indicator system and model. To provide further insight into the impact of geographical and meteorological factors on AE prevalence and establish a theoretical basis for prevention and control. Principal component and regression analysis were used to screen and establish a three-level indicator system. Relative weights were examined to determine the impact of each indicator, and five mathematical models were compared to identify the best predictive model for AE epidemic levels. By analyzing the data downloaded from the China Meteorological Data Service Center and Geospatial Data Cloud, we established the KCBIS, including 50 basic indicators which could be directly obtained online, 15 characteristic indicators which were linear combination of the basic indicators and showed a linear relationship with AE epidemic, and 8 key indicators which were characteristic indicators with a clearer relationships and fewer mixed effects. The relative weight analysis revealed that monthly precipitation, monthly cold days, the difference between negative and positive temperature anomalies, basic air temperature conditions, altitude, the difference between positive and negative atmospheric pressure anomalies, monthy extremely hot days, and monthly fresh breeze days were correlated with the natural logarithm of AE prevalence, with sequential decreases in their relative weights. The multinomial logistic regression model was the best predictor at epidemic levels 1, 3, 5, and 6, whereas the CART model was the best predictor at epidemic levels 2, 4, and 5.

On the coupling of three-level quantum refrigerators in the weak coupling limit

We propose a model of two identical autonomous quantum refrigerators that interact through their qubits coupled to cold thermal baths. We consider the same specific disposition for each refrigerator related to a three-level system coupled to different thermal baths and, in turn, to a qubit as the object to be cooled. By coupling the two systems, we show that under certain conditions on the model parameters, the devices can operate in the regime of an independent autonomous quantum refrigerator or be subject to an adjustment of the thermodynamic performances. We further investigate the correlations induced by the interaction between the two refrigerators, and illustrate their behavior with respect to their thermodynamic performances. We have found that adjusting the different interaction constants of the model can lead to an evolution of the quantum correlations of the two machines that is inversely related to the behavior of the thermodynamic quantities of both refrigerators. However, this is not necessarily the case when the temperatures of the model are considered as the reference parameters.

Hybrid magnon-photon bundle emission from a ferromagnetic-superconducting system

We show that the hybrid magnon-photon bundle emission is possible to generate by employing a three-level Δ-type superconducting artificial atom. The single atom is dispersively coupled with two microwave cavities, one of which simultaneously couples to a yttrium iron garnet (YIG) sphere via the magnetic dipole interaction. Based on the virtual photon exchange, the indirect magnon-atom interaction is established with flexibly tunable coupling strength, thus leading to the consecutive emission of hybrid magnon-photon pairs. The super-Rabi oscillation and Purcell effect make such a hybrid bundle possible in the present three-level system, which is difficult to achieve in the two-level system. The present scheme may find potential applications in quantum information processing and quantum sensing technology. Published by the American Physical Society 2024

Gain-assisted quantum heat engine based on electromagnetically induced transparency

We propose a scheme to realize a gain-assisted quantum heat engine (QHE) based on electromagnetically induced transparency (EIT), which consists of a three-level Λ-type atomic system interacting with two thermal reservoirs and a coupling field. The gain without inversion is induced to the system via spontaneously generated coherence (SGC) between two lower levels. The SGC has significantly affect on the system’s dynamics, resulting in an enhancement of the emission cross-section and spectral brightness of the QHE.

Sustainable Financing for Transport Infrastructure: An Integral Approach for the Russian Federation

The development of global transport infrastructure is a crucial aspect of economic growth and prosperity. In this study, the main trends in the development of global transport infrastructure are analyzed, with a focus on the state and trends in the functioning of the national transport infrastructure of the Russian Federation. By identifying key problems and determinants of financial growth, a preliminary decomposition is made to guide future development. Proceeding from the fact that the innovative development of Russia’s transport infrastructure should occur through state stimulation of the development of intellectual and partnership relationships and the formation of a digital environment for managing projects for its innovative transformation at the state level, this study identifies the goals, methods, and levels of ensuring the implementation of innovative transformations in transport infrastructure. Consideration of the historical aspects of the formation of the modern economy and comprehension of the mechanisms of state management and tools to ensure innovative transformations in the sphere of transport allowed us to identify three stages (dogmatic, strategic regulation, and innovative integration) of transformation regarding the theory of the state management for the innovative development of transport infrastructure in Russia. Taking into account the content of these periods of transformation allowed us to detail the specifics of the modern stage; highlight the shortcomings; and propose theoretical and methodological foundations for revising the provisions of the state regulation of innovative development in transport infrastructure. To determine the effectiveness of the processes of the state regulation of innovation activity in the transport industry, we propose a model for assessing the effectiveness of innovation activity in the transport complex, which is presented in the form of a three-level parametric system, where the first group of indicators allows us to assess the innovation activity of economic entities in the transport industry; the second allows us to assess innovation potential; and the third allows us to assess the effectiveness of innovation. The novelty of the proposed model is the consideration of the principles of dynamism, perspective, and expediency, and its application allows us to establish the level of innovative development in transport infrastructure. An important factor in ensuring the sustainable development of a country’s economy and forming its positive image in the world is its financial attractiveness. Therefore, the assessment of financial attractiveness is a priority task for the development of modern sustainable transport infrastructure in Russia.

Parametric analysis and comprehensive multi-criteria evaluation of double-stage organic Rankine cycle

Double-stage organic Rankine cycle (DORC) is a more effective mechanism of circulation for recovering heat released from industrial wastewater. It is crucial to determine the optimum operating circumstances for the DORC system, and its effectiveness cannot be effectively assessed by applying a single objective evaluation approach. The AHP-entropy analysis method is utilized to establish a three-level assessment system, taking into account several indicators, in order to execute a thorough study of the DORC system. Eight organic fluids, including R113, R124, R1233zd(E), etc, are chosen as the working mediums of the DORC system. The results demonstrate that the heat source temperature exists maximum value that match the working fluids under the impact of the pinch point temperature difference and the critical temperature of the working medium. When the evaporation pressure increases, the whole system performance improves, according to the AHP-entropy analysis of the operating state that corresponds to the single goal optimum value. When the critical temperature of the working medium is approximately 50 °C above the hot water temperature for a given heat source, the system performs more effectively. Additionally, when the heat source temperature is close to the critical temperature of the eight organic fluids, the DORC system operates more effectively.

Azimuthal modulation of light propagation through 1DPCs via efficient nonlinear frequency mixing

The present study aims to investigate the transmitted and reflected light beams from a one-dimensional defect photonic crystal (1DPC) composed of a three-level ladder-type quantum system. The lower leg of the ladder scheme is driven by a weaker probe beam, while the upper leg is driven by a stronger control beam. Unlike natural atoms, this type of model with broken symmetry permits the generation of a sum-frequency signal beam between the majority of higher and lower quantum states, resulting in the formation of a cyclic closed-loop arrangement for the interaction between light and matter. The Laguerre Gaussian (LG) field with strong coupling and a weak probe light interact with the quantum system. A new weak signal light is produced as a result of the system’s symmetric breakdown, and the medium becomes azimuthal dependent. We investigate the spatial dependence of the transmitted and reflected light from a defect 1DPC by using azimuthal modulation of the LG light. Additionally, we will discuss how the absorption spectrum’s spatial modulation varies with winding numbers. We discover that in certain regions, the gain can be realized without population inversion under certain specified parametric parameters.

Goos–Hänchen shifts in a V-type three-level atomic system interacting with squeezed vacuum

This study explores the Goos–Hänchen (GH) shift phenomenon within a cavity hosting a V-type three-level atomic system, engaged with two independent broadband squeezed baths. Our exploration encompasses a thorough analysis of the lateral shifts in both reflected and transmitted light beams, with a focus on the impact of critical factors, i.e, coupling field strength, incoherent pumping field strength, and squeezed vacuum intensity. Our results reveal an interplay of these parameters, resulting in distinctive negative and positive GH shifts in both reflected and transmitted light. In addition, a remarkable enhancement of GH shifts at specific angles of incidence is observed, presenting a wide-ranging modulation across diverse system parameters. This study not only enriches the understanding of the GH shift in complex atomic systems but also highlights the potential for the manipulation of these lateral shifts by fine-tuning key variables of the system, and contributes valuable insights to the broader field of optical phenomena in quantum systems.

Resource and environmental carrying capacity study of Kubai Coalfield in Xinjiang based on RS and GIS

The study of resource and environmental carrying capacity (RECC) is critical to the ecological environmental protection and sustainable development of mining areas. Using multi-source remote sensing data such as Landsat5 and Landsat8, as well as socioeconomic statistics, the impact mechanism of the Kubai Coalfield's RECC was analyzed using the theory of Driving-Pressure-State-Impact-Response (DPSIR), and a three-level evaluation index system of 1-5-18 was proposed. The cloud model enhanced Analytic Hierarchy Process (AHP) was used to estimate the weight value of each assessment index. The Kubai Coalfield's RECC was calculated by superimposing the weights of different variables, and the contributing elements and changing trends of the RECC were investigated. The RECC of the Kubai Coalfield is highest in the east, second highest in the west, and lowest in the center, according to the results. The vegetation cover of the mining area has a direct impact on the RECC, and mining activity is the primary cause of the change in carrying capacity; however, coal mining has a lagging effect on the RECC. The study's findings serve as a guide for the quantitative assessment of RECC of Xinjiang's environmentally vulnerable mining sites and offer theoretical justification for the approach taken in the study of RECC of mining areas and the preservation of ecological environment sources.