Hao Ouyang, Si-Yang Hu, Man-Ling Shen, Chen-Xi Zhang, Xiang-Ai Cheng, and Tian Jiang
Germanium diselenide (GeSe2), a layered IV-VI semiconductor, has an in-plane anisotropic structure and a wide band gap, exhibiting unique optical, electrical, and thermal properties. In this paper, polarization axis Raman spectrum and linear absorption spectrum are used to characterize the crystal axis orientation and energy band characteristics of GeSe2 flake, respectively. Based on the results, a micro-domain I scan system is used to study the optical nonlinear absorption mechanism of GeSe2 near the resonance band. The results show that the nonlinear absorption mechanism in GeSe2 is a superposition of saturation absorption and excited state absorption, and is strongly dependent on the polarization and wavelength of incident light. Under near-resonance excitation (450 nm), the excited state absorption is more greatly dependent on polarization. With different polarizations of incident light, the modulation depth can be changed from 4.6% to 9.9%; for non-resonant excitation (400 nm), the modulation depth only changes from 7.0% to 9.7%. At the same time, compared with saturation absorption, the polarization-dependent excited state absorption is greatly affected by the distance away from the resonance excitation wavelength.Germanium diselenide (GeSe2), a layered IV-VI semiconductor, has an in-plane anisotropic structure and a wide band gap, exhibiting unique optical, electrical, and thermal properties. In this paper, polarization axis Raman spectrum and linear absorption spectrum are used to characterize the crystal axis orientation and energy band characteristics of GeSe2 flake, respectively. Based on the results, a micro-domain I scan system is used to study the optical nonlinear absorption mechanism of GeSe2 near the resonance band. The results show that the nonlinear absorption mechanism in GeSe2 is a superposition of saturation absorption and excited state absorption, and is strongly dependent on the polarization and wavelength of incident light. Under near-resonance excitation (450 nm), the excited state absorption is more greatly dependent on polarization. With different polarizations of incident light, the modulation depth can be changed from 4.6% to 9.9%; for non-resonant excitation (400 nm), the modulation depth only changes from 7.0% to 9.7%. At the same time, compared with saturation absorption, the polarization-dependent excited state absorption is greatly affected by the distance away from the resonance excitation wavelength.
- Sep. 20, 2020
- Acta Physica Sinica
- Vol. 69, Issue 18, 184212-1 (2020)
- DOI：10.7498/aps.69.20200443
Xiang Li, Yong Chen, Hao Feng, and Lei Qi
Acoustically-excited bubble dynamics is the foundation of pipeline bubble detection based on acoustic technology. Due to the existence of multiple bubbles in pipeline flow, the Bjerknes forces among arbitrary bubbles under acoustic excitation may enforce bubble-bubble interaction and then change the features of bubble dynamics. Based on traditional free bubble’s Rayleigh-Plesset (R-P) model, this paper tries to establish bubble-bubble interaction model in consideration of the second Bjerknes force and bubble distribution in the pipeline axial direction. Meanwhile, the influence of finite wave speed in compressible fluid is considered. The proposed model is numerically calculated by the fourth-order Runge-Kutta method. Firstly, the differences in bubble feature between the free bubble’s R-P model and bubble-bubble interaction model are compared under excitation with different frequencies and amplitudes. Results show that the differences in bubble dynamics are minor when the bubble’s distance is large enough. When the bubble’s distance is fixed, the differences are significant on condition that the frequency of acoustic excitation is nearly the resonant frequency of bubbles. Secondly, through establishing compressible model and incompressible fluid model, we compare the differences between the two models. Numerical calculations show that the second Bjerknes force under the compressible assumption acts as an external force and forces the bubble to vibrate. On the other hand, the second Bjerknes force under the incompressible assumption changes the dynamics of bubble-bubble interaction as well as the resonant features. Finally, we study the effect of bubble-bubble distance and bubble’s axial position on bubble vibration characteristics. The bubble-bubble distance affects the second Bjerknes force and may lead the bubbles to vibrate nonlinearly. The bubble’s axial position changes the phase of external acoustic force and leads to the difference in initial vibration feature. When this difference is coupled with the second Bjerknes force, the bubble-bubble interaction may be changed even into nonlinear vibration, leading the bubble’s oscillation spectrum to differ from linear vibrations significantly. These results demonstrate that the resonant state of a small bubble may be converted into nonlinear vibration state if the second Bjerknes force is present. On the other hand, the resonant state of a large bubble can keep linear vibration when the second Bjerknes force is not obvious.Acoustically-excited bubble dynamics is the foundation of pipeline bubble detection based on acoustic technology. Due to the existence of multiple bubbles in pipeline flow, the Bjerknes forces among arbitrary bubbles under acoustic excitation may enforce bubble-bubble interaction and then change the features of bubble dynamics. Based on traditional free bubble’s Rayleigh-Plesset (R-P) model, this paper tries to establish bubble-bubble interaction model in consideration of the second Bjerknes force and bubble distribution in the pipeline axial direction. Meanwhile, the influence of finite wave speed in compressible fluid is considered. The proposed model is numerically calculated by the fourth-order Runge-Kutta method. Firstly, the differences in bubble feature between the free bubble’s R-P model and bubble-bubble interaction model are compared under excitation with different frequencies and amplitudes. Results show that the differences in bubble dynamics are minor when the bubble’s distance is large enough. When the bubble’s distance is fixed, the differences are significant on condition that the frequency of acoustic excitation is nearly the resonant frequency of bubbles. Secondly, through establishing compressible model and incompressible fluid model, we compare the differences between the two models. Numerical calculations show that the second Bjerknes force under the compressible assumption acts as an external force and forces the bubble to vibrate. On the other hand, the second Bjerknes force under the incompressible assumption changes the dynamics of bubble-bubble interaction as well as the resonant features. Finally, we study the effect of bubble-bubble distance and bubble’s axial position on bubble vibration characteristics. The bubble-bubble distance affects the second Bjerknes force and may lead the bubbles to vibrate nonlinearly. The bubble’s axial position changes the phase of external acoustic force and leads to the difference in initial vibration feature. When this difference is coupled with the second Bjerknes force, the bubble-bubble interaction may be changed even into nonlinear vibration, leading the bubble’s oscillation spectrum to differ from linear vibrations significantly. These results demonstrate that the resonant state of a small bubble may be converted into nonlinear vibration state if the second Bjerknes force is present. On the other hand, the resonant state of a large bubble can keep linear vibration when the second Bjerknes force is not obvious.
- Sep. 20, 2020
- Acta Physica Sinica
- Vol. 69, Issue 18, 184703-1 (2020)
- DOI：10.7498/aps.69.20200546
Bin Liu, Peng-Xiang Zhao, Xia Zhao, Yue Luo, and Li-Chao Zhang
Underwater optical imaging is the key technology to explore the underwater mystery. However, due to the absorption and backscattering effects of the media in the underwater environment, the image acquired by the detector will be severely degraded. In order to obtain the effective underwater scene information, it is necessary to restore the acquired underwater image. The restoration technology based on differential polarization is one of the main methods of restoring the underwater images, which can suppress the background scattered light by the common-mode suppression between orthogonal polarization graphs, thus realizing the restoration of underwater image. However, the relevant research shows that the restoration effect of this method is general for the underwater non-uniform light field. The main reason is that the estimation errors of polarization degree and background scattering intensity under the condition of the non-uniform underwater light field are large. Out of the above problem, in this paper we present the multiple aperture underwater imaging technology of fused polarization information. The method uses the camera array to realize the large virtual aperture imaging system, thus obtaining the wide-angle light field information, and then to fuse the depth information of the scene to realize the accurate estimation of background scattering light intensity and polarization degree under the condition of underwater non-uniform light field. The estimated parameter value can better reflect the global characteristics of the scene. Through the imaging experiments on the targets with different polarization degrees in the turbid underwater environment, comparing with the current advanced restoration algorithm, the results show that the proposed method can effectively solve the problems of background scattering and polarization degree significant estimation error caused by non-uniform underwater light field, and obtain high-quality restoration results. Through the contrast imaging experiment of the target in the underwater environment with different turbidity concentrations, the results show that with the increase of turbidity concentration of the water, the image recovery effect of the method in this paper is gradually weakened. However, it still has a good restoration effect at a large concentration. At the same time, imaging experiments are conducted on targets in underwater environments with different sediment concentrations. The results show that the method proposed in this paper can also obtain a better restoration image in the turbid water environment containing sediment.Underwater optical imaging is the key technology to explore the underwater mystery. However, due to the absorption and backscattering effects of the media in the underwater environment, the image acquired by the detector will be severely degraded. In order to obtain the effective underwater scene information, it is necessary to restore the acquired underwater image. The restoration technology based on differential polarization is one of the main methods of restoring the underwater images, which can suppress the background scattered light by the common-mode suppression between orthogonal polarization graphs, thus realizing the restoration of underwater image. However, the relevant research shows that the restoration effect of this method is general for the underwater non-uniform light field. The main reason is that the estimation errors of polarization degree and background scattering intensity under the condition of the non-uniform underwater light field are large. Out of the above problem, in this paper we present the multiple aperture underwater imaging technology of fused polarization information. The method uses the camera array to realize the large virtual aperture imaging system, thus obtaining the wide-angle light field information, and then to fuse the depth information of the scene to realize the accurate estimation of background scattering light intensity and polarization degree under the condition of underwater non-uniform light field. The estimated parameter value can better reflect the global characteristics of the scene. Through the imaging experiments on the targets with different polarization degrees in the turbid underwater environment, comparing with the current advanced restoration algorithm, the results show that the proposed method can effectively solve the problems of background scattering and polarization degree significant estimation error caused by non-uniform underwater light field, and obtain high-quality restoration results. Through the contrast imaging experiment of the target in the underwater environment with different turbidity concentrations, the results show that with the increase of turbidity concentration of the water, the image recovery effect of the method in this paper is gradually weakened. However, it still has a good restoration effect at a large concentration. At the same time, imaging experiments are conducted on targets in underwater environments with different sediment concentrations. The results show that the method proposed in this paper can also obtain a better restoration image in the turbid water environment containing sediment.
- Sep. 20, 2020
- Acta Physica Sinica
- Vol. 69, Issue 18, 184202-1 (2020)
- DOI：10.7498/aps.69.20200471
Yi-Quan Xu, and Cong Wang
The leap in communication technology in recent years has brought new challenges to the compactness, modulation speed, working bandwidth and control efficiency of modulation equipment. The discovery of graphene has led the two-dimensional materials to develop rapidly, and a series of new materials have continuously emerged, such as MXene, black phosphorus, transition metal sulfides, etc. These new two-dimensional materials have excellent nonlinear optical effects, strong light-matter interaction, and ultra-wide working bandwidth. Using their thermo-optic effect, nonlinear effect and the combination with optical structure, the needs of ultra-fast modulation in optical communication can be met. Compact, ultra-fast, and ultra-wide will become the tags for all-optical modulation of two-dimensional materials in the future. This article focuses on all-optical devices based on thermo-optical effects and non-linear effects of two-dimensional materials, and introduces fiber-type Mach-Zehnder interferometer structures, Michelson interferometer structures, polarization interferometer structures, and micro-ring structures. In this paper, the development status of all-optical devices is discussed from the perspectives of response time, loss, driving energy, extinction ratio, and modulation depth. Finally, we review the latest developments, analyze the challenges and opportunities faced by all-optical devices, and propose that all-optical devices should be developed in the direction of ring resonators and finding better new two-dimensional materials. We believe that all-optical devices will maintain high-speed development, acting as a cornerstone to promote the progress of all-optical systems.The leap in communication technology in recent years has brought new challenges to the compactness, modulation speed, working bandwidth and control efficiency of modulation equipment. The discovery of graphene has led the two-dimensional materials to develop rapidly, and a series of new materials have continuously emerged, such as MXene, black phosphorus, transition metal sulfides, etc. These new two-dimensional materials have excellent nonlinear optical effects, strong light-matter interaction, and ultra-wide working bandwidth. Using their thermo-optic effect, nonlinear effect and the combination with optical structure, the needs of ultra-fast modulation in optical communication can be met. Compact, ultra-fast, and ultra-wide will become the tags for all-optical modulation of two-dimensional materials in the future. This article focuses on all-optical devices based on thermo-optical effects and non-linear effects of two-dimensional materials, and introduces fiber-type Mach-Zehnder interferometer structures, Michelson interferometer structures, polarization interferometer structures, and micro-ring structures. In this paper, the development status of all-optical devices is discussed from the perspectives of response time, loss, driving energy, extinction ratio, and modulation depth. Finally, we review the latest developments, analyze the challenges and opportunities faced by all-optical devices, and propose that all-optical devices should be developed in the direction of ring resonators and finding better new two-dimensional materials. We believe that all-optical devices will maintain high-speed development, acting as a cornerstone to promote the progress of all-optical systems.
- Sep. 20, 2020
- Acta Physica Sinica
- Vol. 69, Issue 18, 184216-1 (2020)
- DOI：10.7498/aps.69.20200654
Yan-Ju Wei, Jie Zhang, Sheng-Cai Deng, Ya-Jie Zhang, Ya-Jing Yang, Sheng-Hua Liu, and Hao Chen
Atomization of droplets is ubiquitous in many natural and industrial processes, such as falling rain drops, inkjet printing, fuel injection in automotive and gas-turbine engines. Acoustic irradiation provides a very effective method of atomizing fluid. However, the acoustic atomization of acoustically levitated droplet is seldom studied. To assess the possibility of achieving ultrafine atomization, we, in this paper, systematically study the atomization of an acoustically levitated droplet placed in a hot gas of a flame. High speed camera is utilized to investigate the atomization characteristics of various droplets with diameters ranging from 0.5 mm to 3.5 mm.The experimental results show that the sound pressure of the resonance acoustic field has the ability to atomize the droplet when it is suddenly bathed in hot gas. Here the heating acts as a switch to convert the droplet surface from an acoustic isolator to conductor by heating the surface to strong evaporation. The presence of a high concentration of vapor molecules surrounding the droplet caused the acoustic field to change, thus, a much larger pressure gradient is established along the droplet surface, resulting in the atomization of droplet from the equator. Furthermore, Faraday wave stimulation and discretization on the film cause the droplet to further disintegrate when the droplet diameter is large enough. The atomization consists of three different styles, i.e. rim spray (RS), film disintegration (FD) and normal sputtering (NS). When exposed to hot gas, the droplets with equivalent diameter D0 D0 > 3.2 mm undergo further film buckling, forming a closed bubble due to the Helmholtz resonator effect and NS at the bottom. This sound driven atomization of droplets enriches the understanding of fluid mechanism in multi-physical fields, and may provide new ideas for relative application research.
- Sep. 20, 2020
- Acta Physica Sinica
- Vol. 69, Issue 18, 184702-1 (2020)
- DOI：10.7498/aps.69.20200562
Zhou-Xiao-Song Zeng, Xiao Wang, and An-Lian Pan
Two-dimensionl (2D) layered transition metal dichalcogenides (TMDCs) have received great attention in integrated on-chip photonic and photoelectric applications due to their unique physical properties including indirect-to-direct optical bandgap transition, broad bandgap from visible band to near-infrared band, as well as their excellent optoelectric properties derived from the 2D confinement. Recently, with the in-depth study of their fundament nonlinear optical properties, these 2D layered TMDCs have displayed significant potential applications in nonlinear optical devices. In this review, we focus on recent research progress of second harmonic generation (SHG) studies of TMDCs. Firstly, we briefly introduce the basic theory of nonlinear optics (mainly about SHG). Secondly, the several intrinsic SHG relative properties in TMDCs including layer dependence, polarization dependence, exciton resonance effect, valley selection rule are discussed. Thirdly, the latest SHG modulation and enhancement studies are presented, where the electric field, strain, plasmonic structure and micro-cavity enhancement are covered. Finally, we will summarize and give a perspective of possible research direction in the future. We believe that a more in-depth understanding of the SHG process in 2D layered TMDCs as well as the material structure and modulation effects paves the way for further developing the ultra-thin, multifunctional 2D nonlinear optical devices.Two-dimensionl (2D) layered transition metal dichalcogenides (TMDCs) have received great attention in integrated on-chip photonic and photoelectric applications due to their unique physical properties including indirect-to-direct optical bandgap transition, broad bandgap from visible band to near-infrared band, as well as their excellent optoelectric properties derived from the 2D confinement. Recently, with the in-depth study of their fundament nonlinear optical properties, these 2D layered TMDCs have displayed significant potential applications in nonlinear optical devices. In this review, we focus on recent research progress of second harmonic generation (SHG) studies of TMDCs. Firstly, we briefly introduce the basic theory of nonlinear optics (mainly about SHG). Secondly, the several intrinsic SHG relative properties in TMDCs including layer dependence, polarization dependence, exciton resonance effect, valley selection rule are discussed. Thirdly, the latest SHG modulation and enhancement studies are presented, where the electric field, strain, plasmonic structure and micro-cavity enhancement are covered. Finally, we will summarize and give a perspective of possible research direction in the future. We believe that a more in-depth understanding of the SHG process in 2D layered TMDCs as well as the material structure and modulation effects paves the way for further developing the ultra-thin, multifunctional 2D nonlinear optical devices.
- Sep. 20, 2020
- Acta Physica Sinica
- Vol. 69, Issue 18, 184210-1 (2020)
- DOI：10.7498/aps.69.20200452
Zheng-Yuan Zhang, Tian-Yi Zhang, Zong-Kai Liu, Dong-Sheng Ding, and Bao-Sen Shi
The interaction of many-body quantum system is a critical problem to be solved in the field of quantum information science. Rydberg atoms have large dipole moment, enabling them to interact with others in a long range, thereby offering us a powerful tool for studying many-body quantum physics. Meanwhile, atoms in the ground state are stable, which makes it easy to manipulate them. Therefore, Rydberg-atom many-body system is an ideal platform for studying the interaction of many-body quantum system. Studies of Rydberg-atom many-body system may contribute to understanding the properties of many-body system and putting the interaction of many-body quantum system into practical applications. In this review, we introduce some studies of properties of interaction of Rydberg-atom many-body system, including the Rydberg excitation blockade, the variation of Rabi frequencies of the many-body system and special spatial distribution of Rydberg atoms in a many-body system. Firstly, the Rydberg excitation blockade, the most important property in the Rydberg-atom many-body system, indicates that atoms’ excitation will be suppressed in a certain range around one Rydberg excitation because the interaction between the Rydberg excitation and atoms leads the energy level to shift so that atoms cannot be excited by the same pulse. Secondly, there is a collective Rabi frequency in the system, which is proportional to the square of the number of atoms in the suppressed area. And additionally, because of the Rydberg blockade effect, Rydberg excitations in the ensemble cannot be at casual positions but a regular distribution is formed. Besides the studies of properties, several researches on the applications of interaction of Rydberg-atom many-body system are introduced, including single-photon source, quantum storage, single-atom imaging, quantum simulation, etc. These applications contribute to the development of quantum community and quantum computing, which may bring us a quantum-technology time. Finally, we discuss the future development of Rydberg-atom many-body system and its further applications. Further development includes the development of many-body system with a larger number of atoms, the development of many-body system of atoms with more than one electron, and some other specific subjects based on many-system, such as Rydberg dimer and topological phase. Also some promising applications such as in studying optimization problem by quantum annealing, may become true.The interaction of many-body quantum system is a critical problem to be solved in the field of quantum information science. Rydberg atoms have large dipole moment, enabling them to interact with others in a long range, thereby offering us a powerful tool for studying many-body quantum physics. Meanwhile, atoms in the ground state are stable, which makes it easy to manipulate them. Therefore, Rydberg-atom many-body system is an ideal platform for studying the interaction of many-body quantum system. Studies of Rydberg-atom many-body system may contribute to understanding the properties of many-body system and putting the interaction of many-body quantum system into practical applications. In this review, we introduce some studies of properties of interaction of Rydberg-atom many-body system, including the Rydberg excitation blockade, the variation of Rabi frequencies of the many-body system and special spatial distribution of Rydberg atoms in a many-body system. Firstly, the Rydberg excitation blockade, the most important property in the Rydberg-atom many-body system, indicates that atoms’ excitation will be suppressed in a certain range around one Rydberg excitation because the interaction between the Rydberg excitation and atoms leads the energy level to shift so that atoms cannot be excited by the same pulse. Secondly, there is a collective Rabi frequency in the system, which is proportional to the square of the number of atoms in the suppressed area. And additionally, because of the Rydberg blockade effect, Rydberg excitations in the ensemble cannot be at casual positions but a regular distribution is formed. Besides the studies of properties, several researches on the applications of interaction of Rydberg-atom many-body system are introduced, including single-photon source, quantum storage, single-atom imaging, quantum simulation, etc. These applications contribute to the development of quantum community and quantum computing, which may bring us a quantum-technology time. Finally, we discuss the future development of Rydberg-atom many-body system and its further applications. Further development includes the development of many-body system with a larger number of atoms, the development of many-body system of atoms with more than one electron, and some other specific subjects based on many-system, such as Rydberg dimer and topological phase. Also some promising applications such as in studying optimization problem by quantum annealing, may become true.
- Sep. 20, 2020
- Acta Physica Sinica
- Vol. 69, Issue 18, 180301-1 (2020)
- DOI：10.7498/aps.69.20200649
Chang Zhao, Qian-Qian Huang, Zi-Nan Huang, Li-Long Dai, Sergey Sergeyev, Aleksey Rozhin, and Cheng-Bo Mou
In this paper, a dissipative soliton mode-locked fiber laser is established based on carbon nanotube in order to study the polarization dynamics of dissipative soliton by using a commercial polarimeter. Under the pump power of 160 mW, stable dissipatives soliton are observed to have a limited cycle polarization trajectory shown on Poincare sphere, indicating the periodic modulation of anisotropy in cavity. The stable dissipative soliton possesses a high signal noise ratio of 57.7 dB at fundamental frequency. Moreover, the fast oscillation of state of polarization leads to a lower degree of polarization (DOP). In addition, the polarization controllers are employed to compensate for the birefringence in the cavity to adjust the ratio between cavity length and birefringence length. As a result, we can observe the polarization evolving from the polarization locked attractor to the limited cycle attractor by adjusting polarization controllers. It is noted that this dynamic polarization trajectory can be manually controlled. By comparing polarization attractor with DOP, it is clear that the size of trajectory shown on Poincare sphere is inversely proportional to DOP. We expect our work to be conducible to studying the physics in lasers and creating a new type of polarization tunable laser.In this paper, a dissipative soliton mode-locked fiber laser is established based on carbon nanotube in order to study the polarization dynamics of dissipative soliton by using a commercial polarimeter. Under the pump power of 160 mW, stable dissipatives soliton are observed to have a limited cycle polarization trajectory shown on Poincare sphere, indicating the periodic modulation of anisotropy in cavity. The stable dissipative soliton possesses a high signal noise ratio of 57.7 dB at fundamental frequency. Moreover, the fast oscillation of state of polarization leads to a lower degree of polarization (DOP). In addition, the polarization controllers are employed to compensate for the birefringence in the cavity to adjust the ratio between cavity length and birefringence length. As a result, we can observe the polarization evolving from the polarization locked attractor to the limited cycle attractor by adjusting polarization controllers. It is noted that this dynamic polarization trajectory can be manually controlled. By comparing polarization attractor with DOP, it is clear that the size of trajectory shown on Poincare sphere is inversely proportional to DOP. We expect our work to be conducible to studying the physics in lasers and creating a new type of polarization tunable laser.
- Sep. 20, 2020
- Acta Physica Sinica
- Vol. 69, Issue 18, 184218-1 (2020)
- DOI：10.7498/aps.69.20201305
Qiang Yu, Kun Guo, Jie Chen, Tao Wang, Jin Wang, Xin-Yao Shi, Jian Wu, Kai Zhang, and Pu Zhou
As a member of the metal phosphorus trichalcogenide family, MPS3 is widely used in nonlinear optics and devices, which can be regarded as a significant benefit for the excellent photonic and optoelectronic properties. In this work, the MnPS3 nanosheet is prepared by the chemical vapor transport method and the MnPS3 saturable absorber is demonstrated by modifying mechanical exfoliation. To the best of our knowledge, the dual-wavelength self-starting mode-locking erbium-doped fiber laser with MnPS3 saturable absorber is demonstrated for the first time. The dual wavelength mode-locked laser with a pulse repetition rate of 5.102 MHz at 1565.19 nm and 1565.63 nm is proposed. Its maximum output power at the dual-wavelength is 27.2 MW. The mode-locked laser can self-start and stably run for more than 280 h.As a member of the metal phosphorus trichalcogenide family, MPS3 is widely used in nonlinear optics and devices, which can be regarded as a significant benefit for the excellent photonic and optoelectronic properties. In this work, the MnPS3 nanosheet is prepared by the chemical vapor transport method and the MnPS3 saturable absorber is demonstrated by modifying mechanical exfoliation. To the best of our knowledge, the dual-wavelength self-starting mode-locking erbium-doped fiber laser with MnPS3 saturable absorber is demonstrated for the first time. The dual wavelength mode-locked laser with a pulse repetition rate of 5.102 MHz at 1565.19 nm and 1565.63 nm is proposed. Its maximum output power at the dual-wavelength is 27.2 MW. The mode-locked laser can self-start and stably run for more than 280 h.
- Sep. 20, 2020
- Acta Physica Sinica
- Vol. 69, Issue 18, 184208-1 (2020)
- DOI：10.7498/aps.69.20200342
Bu-Qing Gong, Xiao-Yu Chen, Wei-Peng Wang, Zhi-Ye Wang, Hua Zhou, and Xiang-Qian Shen
The coupled nano-structure Ag@SiO2 has both plasmon excitation like metallic nanoparticles and diffraction scattering like a dielectric nanosphere, which effectively controls the propagation path and the energy distribution of incident light and shows great potential applications in light trapping for thin film solar cells. In this work, we construct a three-dimensional electromagnetic model based on the finite-difference time-domain (FDTD) and rigorous coupled-wave analysis (RCWA) method to investigate the regulation mechanism of Ag@SiO2 coupling structure to the spectral response of amorphous silicon cells. By being optimally designed, a high-efficiency cell device is achieved. The results show that the transmitted light into the active layer reaches a maximum value when Ag and SiO2 have their feature sizes of 18 and 150 nm, respectively. The absorption spectrum of the corresponding cell device also arrives at its maximum value. The photoelectric conversion efficiency is enhanced from 7.19% to 7.80%, with an increment of 8.48% compared with the flat solar cell with an equivalent thickness of absorbing layer.The coupled nano-structure Ag@SiO2 has both plasmon excitation like metallic nanoparticles and diffraction scattering like a dielectric nanosphere, which effectively controls the propagation path and the energy distribution of incident light and shows great potential applications in light trapping for thin film solar cells. In this work, we construct a three-dimensional electromagnetic model based on the finite-difference time-domain (FDTD) and rigorous coupled-wave analysis (RCWA) method to investigate the regulation mechanism of Ag@SiO2 coupling structure to the spectral response of amorphous silicon cells. By being optimally designed, a high-efficiency cell device is achieved. The results show that the transmitted light into the active layer reaches a maximum value when Ag and SiO2 have their feature sizes of 18 and 150 nm, respectively. The absorption spectrum of the corresponding cell device also arrives at its maximum value. The photoelectric conversion efficiency is enhanced from 7.19% to 7.80%, with an increment of 8.48% compared with the flat solar cell with an equivalent thickness of absorbing layer.
- Sep. 20, 2020
- Acta Physica Sinica
- Vol. 69, Issue 18, 188801-1 (2020)
- DOI：10.7498/aps.69.20200334
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