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Nonlinear Optics|83 Article(s)
One-Dimensional Modulational Instability of Broad Optical Beams In Photorefractive Crystals with Both Linear and Quadratic Electro-Optic Effects
Lili Hao, Zhen Wang, Hongxia Tang, Xiaoyang Zhang, Qi Yang, and Qiang Wang
We present a theoretical study of the one-dimensional modulational instability of a broad optical beam propagating in a biased photorefractive crystal with both linear and quadratic electro-optic effects (Kerr effect) under steady-state conditions. One-dimensional modulational instability growth rates are obtained by treating the space-charge field equation globally and locally. Both theoretical reasoning and numerical simulation show that both the global and local modulational instability gains are governed simultaneously by the strength and the polarity of external bias field and by the ratio of the intensity of the broad beam to that of the dark irradiance. Under a strong bias field, the results obtained using these two methods are in good agreement in the low spatial frequency regime. Moreover, the instability growth rate increases with the bias field, and the maximum instability growth occurs when ratio of light intensity to dark irradiance is 0.88. We present a theoretical study of the one-dimensional modulational instability of a broad optical beam propagating in a biased photorefractive crystal with both linear and quadratic electro-optic effects (Kerr effect) under steady-state conditions. One-dimensional modulational instability growth rates are obtained by treating the space-charge field equation globally and locally. Both theoretical reasoning and numerical simulation show that both the global and local modulational instability gains are governed simultaneously by the strength and the polarity of external bias field and by the ratio of the intensity of the broad beam to that of the dark irradiance. Under a strong bias field, the results obtained using these two methods are in good agreement in the low spatial frequency regime. Moreover, the instability growth rate increases with the bias field, and the maximum instability growth occurs when ratio of light intensity to dark irradiance is 0.88.
Laser & Optoelectronics Progress
- Publication Date: Mar. 10, 2024
- Vol. 61, Issue 5, 0519001 (2024)
Influence of the Airy Pulse on Rogue Waves and its Regulation in a Supercontinuum (Invited)
Shuo Liu, Congying Yin, Qun Zu, Yuhang Dong, Qi Li, and Saili Zhao
The oscillating tailing shape and spectrum of the decelerated finite-energy Airy pulse are influenced by various parameters. This study examined the impacts of peak power, width, initial chirp, truncation coefficient, and distribution factor of the Airy pulse on the generation of rogue waves in a supercontinuum (SC) as well as the SC coherence and stability. The findings reveal that altering these parameters can regulate the rogue waves and affect the SC coherence and stability. Moreover, a multiobjective particle-swarm optimization algorithm is used to simultaneously optimize the five pulse parameters. By using the average peak power of 500 analog output solitons (i.e., twice of that required for generating the rogue waves) and considering the number and distribution of rogue waves among the solitons as optimization objectives, this study identifies optimal parameters for the Airy pulse. These parameters either promote or suppress the generation of rogue waves, enabling controlled manipulation of rogue wave generation within the SC. The oscillating tailing shape and spectrum of the decelerated finite-energy Airy pulse are influenced by various parameters. This study examined the impacts of peak power, width, initial chirp, truncation coefficient, and distribution factor of the Airy pulse on the generation of rogue waves in a supercontinuum (SC) as well as the SC coherence and stability. The findings reveal that altering these parameters can regulate the rogue waves and affect the SC coherence and stability. Moreover, a multiobjective particle-swarm optimization algorithm is used to simultaneously optimize the five pulse parameters. By using the average peak power of 500 analog output solitons (i.e., twice of that required for generating the rogue waves) and considering the number and distribution of rogue waves among the solitons as optimization objectives, this study identifies optimal parameters for the Airy pulse. These parameters either promote or suppress the generation of rogue waves, enabling controlled manipulation of rogue wave generation within the SC.
Laser & Optoelectronics Progress
- Publication Date: Feb. 10, 2024
- Vol. 61, Issue 3, 0319001 (2024)
Stimulated Phonon Polariton and Terahertz Physics (Invited)
Qiang Wu, Yao Lu, Ruobin Ma, Xitan Xu, Yibo Huang, and Jingjun Xu
More than 70 years ago, Prof. Huang Kun proposed the famous “Huang's equations” and the concept of “phonon polariton”, marking the beginning of polariton research. So far, the Huang Kun equation, named after a local Chinese scientist, remains one of the best theories for describing polaritons. In the following decades, with the rapid development of ultrafast optics, nanooptics, and terahertz physics and technology, phonon polaritons have once again become a hot research frontier. The related research on surface phonon polaritons has brought new dimensions to the localization and control of electromagnetic waves. In recent years, the team at Nankai University has developed the Huang's equations and proposed the concept of “stimulated phonon polaritons”, gradually opening the door to the study of light matter interactions in which phonon polaritons participate and lead. Various terahertz applications integrated on lithium niobate chips based on stimulated phonon polaritons have also benefited from this and achieved significant development. This article will review the relevant concepts of phonon polaritons and stimulated phonon polaritons, introduce the interaction system between light and matter under the participation of stimulated phonon polaritons, and take research on terahertz nonlinear optics and lithium niobate chip integration as examples to explain the recent development of phonon polaritons and terahertz physics. More than 70 years ago, Prof. Huang Kun proposed the famous “Huang's equations” and the concept of “phonon polariton”, marking the beginning of polariton research. So far, the Huang Kun equation, named after a local Chinese scientist, remains one of the best theories for describing polaritons. In the following decades, with the rapid development of ultrafast optics, nanooptics, and terahertz physics and technology, phonon polaritons have once again become a hot research frontier. The related research on surface phonon polaritons has brought new dimensions to the localization and control of electromagnetic waves. In recent years, the team at Nankai University has developed the Huang's equations and proposed the concept of “stimulated phonon polaritons”, gradually opening the door to the study of light matter interactions in which phonon polaritons participate and lead. Various terahertz applications integrated on lithium niobate chips based on stimulated phonon polaritons have also benefited from this and achieved significant development. This article will review the relevant concepts of phonon polaritons and stimulated phonon polaritons, introduce the interaction system between light and matter under the participation of stimulated phonon polaritons, and take research on terahertz nonlinear optics and lithium niobate chip integration as examples to explain the recent development of phonon polaritons and terahertz physics.
Laser & Optoelectronics Progress
- Publication Date: Jan. 10, 2024
- Vol. 61, Issue 1, 0119001 (2024)
Population Inversion Under Driven of Double Laser Fields
Guiyin Zhang, Xiaorui Wu, Songtao Li, and Haiming Zheng
Based on the open trapezoidal three-energy level atomic model and density matrix equation theory, the variation of population with time during double-color and double-resonant enhanced multiphoton ionization is numerically simulated under different parameters. When the frequency detuning of two lasers is zero, the populations of the ground as well as first- and second-excited states exhibit damping Rabi oscillation with time. The oscillation frequency of the population distributed in the first-excited state is twice that in the ground and second-excited states. Large population inversion occurs between the second-excited and ground states and exhibits the possibility for the output of coherent light with short wavelengths. Furthermore, the oscillation frequency and population inversion increase with Rabi frequency. Population inversion is evident as the two lasers become synchronous. Based on the open trapezoidal three-energy level atomic model and density matrix equation theory, the variation of population with time during double-color and double-resonant enhanced multiphoton ionization is numerically simulated under different parameters. When the frequency detuning of two lasers is zero, the populations of the ground as well as first- and second-excited states exhibit damping Rabi oscillation with time. The oscillation frequency of the population distributed in the first-excited state is twice that in the ground and second-excited states. Large population inversion occurs between the second-excited and ground states and exhibits the possibility for the output of coherent light with short wavelengths. Furthermore, the oscillation frequency and population inversion increase with Rabi frequency. Population inversion is evident as the two lasers become synchronous.
Laser & Optoelectronics Progress
- Publication Date: Apr. 10, 2023
- Vol. 60, Issue 7, 0719001 (2023)
Second Harmonic Characteristics of Three Crystals Based on Quantum Impedance Lorentz Oscillator
Qiqi Bai, Kai Li, Xiaofeng Wang, Yu Yu, Yulei Wang, Yong Zhang, Peide Zhao, and Yuanqin Xia
Quantum impedance Lorentz oscillator (QILO) is a newly established model for quantizing Lorentz oscillators based on Bohr-Somerfeld theory and quantum mechanical selection rules. Based on this model, the second harmonic characteristics of Li2SnTeO6, CsClO3, and Na2Nb4O11 optical crystals were analyzed and numerically simulated, and a method for estimating the second-order nonlinear optical coefficients of crystals was proposed. First, we calculated the effective quantum numbers before and after the atomic transition according to the peak frequency and full width at half maximum of the optical crystals. Then, considering the second nonlinear effective parameter of QILO, we inferred and determined the second-order polarizability of the three crystals as a function of wavelength. As a result, the second harmonic generation coefficients of the three crystals at 532 nm were 0.17 pm/V, 0.69 pm/V, and 1.17 pm/V, respectively, which agree well with those from the first principle. The results show that the second-order electric susceptibility based on QILO model is helpful to analyze and improve the efficiency of sum frequency, difference frequency, and frequency multiplication of materials, and the method is simple, calculation time is less, and calculation efficiency is high. Quantum impedance Lorentz oscillator (QILO) is a newly established model for quantizing Lorentz oscillators based on Bohr-Somerfeld theory and quantum mechanical selection rules. Based on this model, the second harmonic characteristics of Li2SnTeO6, CsClO3, and Na2Nb4O11 optical crystals were analyzed and numerically simulated, and a method for estimating the second-order nonlinear optical coefficients of crystals was proposed. First, we calculated the effective quantum numbers before and after the atomic transition according to the peak frequency and full width at half maximum of the optical crystals. Then, considering the second nonlinear effective parameter of QILO, we inferred and determined the second-order polarizability of the three crystals as a function of wavelength. As a result, the second harmonic generation coefficients of the three crystals at 532 nm were 0.17 pm/V, 0.69 pm/V, and 1.17 pm/V, respectively, which agree well with those from the first principle. The results show that the second-order electric susceptibility based on QILO model is helpful to analyze and improve the efficiency of sum frequency, difference frequency, and frequency multiplication of materials, and the method is simple, calculation time is less, and calculation efficiency is high.
Laser & Optoelectronics Progress
- Publication Date: Nov. 10, 2023
- Vol. 60, Issue 21, 2119001 (2023)
Ultrafast Third-Order Optical Nonlinearity of ZnO Crystals with Different Crystal Planes and Doping
Mingkai Wang, Zhengguo Xiao, and Zhongquan Nie
In this study, ultrafast third-order optical nonlinearity of ZnO crystals with different crystal planes and doping under femtosecond linearly/radially polarized light (330 fs, 532 nm) excitation is investigated. First, the band gap of ZnO crystals is analyzed using an ultraviolet-visible spectroscopy absorption spectrum. Next, the third-order optical nonlinearity of the ZnO crystals under femtosecond linearly/radially polarized light is measured using the Z-scan technique. The results show that the nonlinear saturation absorption effect and self-focusing effect are observed in ZnO crystals with different crystal planes and doping under the excitation of linearly and radially polarized lights owing to the electron transition in the defect state of the ZnO crystals. The third-order optical nonlinearity of ZnO[101] is the strongest for femtosecond linearly polarized light excitation, owing to the third-order optical nonlinearity of near-resonance enhancement caused by the narrowed energy bandgap in ZnO crystals. However, under the excitation of radially polarized light, ZnO[110] has the strongest third-order optical nonlinearity, probably owing to the combination of the narrow energy bandgap and the anisotropic nonlinearity caused by the axisymmetric polarization of the femtosecond vector laser. This study has potential application value in saturable absorbers, ultrafast light field regulation, and super-resolution imaging. In this study, ultrafast third-order optical nonlinearity of ZnO crystals with different crystal planes and doping under femtosecond linearly/radially polarized light (330 fs, 532 nm) excitation is investigated. First, the band gap of ZnO crystals is analyzed using an ultraviolet-visible spectroscopy absorption spectrum. Next, the third-order optical nonlinearity of the ZnO crystals under femtosecond linearly/radially polarized light is measured using the Z-scan technique. The results show that the nonlinear saturation absorption effect and self-focusing effect are observed in ZnO crystals with different crystal planes and doping under the excitation of linearly and radially polarized lights owing to the electron transition in the defect state of the ZnO crystals. The third-order optical nonlinearity of ZnO[101] is the strongest for femtosecond linearly polarized light excitation, owing to the third-order optical nonlinearity of near-resonance enhancement caused by the narrowed energy bandgap in ZnO crystals. However, under the excitation of radially polarized light, ZnO[110] has the strongest third-order optical nonlinearity, probably owing to the combination of the narrow energy bandgap and the anisotropic nonlinearity caused by the axisymmetric polarization of the femtosecond vector laser. This study has potential application value in saturable absorbers, ultrafast light field regulation, and super-resolution imaging.
Laser & Optoelectronics Progress
- Publication Date: Oct. 10, 2023
- Vol. 60, Issue 19, 1919001 (2023)
Influence Analysis of Thermo-Optic Effect on Generation and Evolution of Silicon-on-Insulator Microcavity Optical Comb
Keyu Xiong, Jin Wen, Chenyao He, Bozhi Liang, Wei Sun, Hui Zhang, Qian Wang, Zhengwei Wu, and Huimin Yu
Microcavity optical frequency combs exhibit low power consumption, integration, and tunable comb spacing, and they have been widely used in many fields. The technology for processing silicon-on-insulator (SOI) materials is compatible with the existing complementary metal-oxide-semiconductor (CMOS) process, making it one of the most promising photonic platforms. In this study, a silicon-based micro-ring resonator with a ridge section was designed, and the effects of various geometric parameters on the dispersion of the micro-ring resonator were investigated. The thermal dynamic equation of the micro-ring resonator was numerically solved, and the effects of different parameters on the thermal dynamic influence of the micro-ring resonator were analyzed. The Lugiato-Lefever equation (LLE) model was solved numerically. Because the thermo-optic effect was ignored in the theoretical research on SOI microcavity optical frequency comb, the influence of the thermo-optic effect on the generation and evolution of the optical frequency comb was analyzed. The numerical results show that at 0?0.16 °C, the maximum power of the light field increases by 22% in the time domain, and the optical frequency comb broadens by 221 nm in the frequency domain. Finally, the output spectrum of the optical frequency comb under two kinds of thermo-optic effects was analyzed. The results show that the bandwidth of the optical frequency comb is expanded by 353 nm compared with that at 0?0.16 °C when the temperature range of the thermo-optic effect is 0?0.32 °C. Microcavity optical frequency combs exhibit low power consumption, integration, and tunable comb spacing, and they have been widely used in many fields. The technology for processing silicon-on-insulator (SOI) materials is compatible with the existing complementary metal-oxide-semiconductor (CMOS) process, making it one of the most promising photonic platforms. In this study, a silicon-based micro-ring resonator with a ridge section was designed, and the effects of various geometric parameters on the dispersion of the micro-ring resonator were investigated. The thermal dynamic equation of the micro-ring resonator was numerically solved, and the effects of different parameters on the thermal dynamic influence of the micro-ring resonator were analyzed. The Lugiato-Lefever equation (LLE) model was solved numerically. Because the thermo-optic effect was ignored in the theoretical research on SOI microcavity optical frequency comb, the influence of the thermo-optic effect on the generation and evolution of the optical frequency comb was analyzed. The numerical results show that at 0?0.16 °C, the maximum power of the light field increases by 22% in the time domain, and the optical frequency comb broadens by 221 nm in the frequency domain. Finally, the output spectrum of the optical frequency comb under two kinds of thermo-optic effects was analyzed. The results show that the bandwidth of the optical frequency comb is expanded by 353 nm compared with that at 0?0.16 °C when the temperature range of the thermo-optic effect is 0?0.32 °C.
Laser & Optoelectronics Progress
- Publication Date: Sep. 10, 2023
- Vol. 60, Issue 17, 1719001 (2023)
Propagation and Control of Airy-Gaussian Beams in Gaussian Parity-Time Symmetric Media
Zhengchun Zhao, Bing Wen, Yangbao Deng, and Bing Yang
In this study, the propagation and control of Airy-Gaussian beams in Gaussian parity-time (PT) symmetric media are investigated numerically, by utilizing the nonlinear Schrödinger equation as a theoretical model. The impacts of the characteristic parameters of Gaussian PT symmetric media (modulation depth P, modulation factor ω, and gain/loss factor W0) and the characteristic parameters of Airy-Gaussian beams (truncation factor a, distribution factor χ0) on propagation characteristics of Airy-Gaussian beams are examined in detail. The results demonstrate that the Airy-Gaussian beams can produce oscillating solitons and transmit steadily in Gaussian PT symmetric media. The soliton strength increases with the increase of P, W0, and a, and decreases with the increase of ω. The oscillation period decreases with the increase of P and ω and increases with the increase of W0. When χ0 increases, when 0<χ0<0.55, the peak intensity of the soliton does not change obviously; when χ0>0.55, the peak intensity of the soliton decreases rapidly. This research can offer a theoretical foundation for the use of soliton transmission in complicated heterogeneous media and all-optical control. In this study, the propagation and control of Airy-Gaussian beams in Gaussian parity-time (PT) symmetric media are investigated numerically, by utilizing the nonlinear Schrödinger equation as a theoretical model. The impacts of the characteristic parameters of Gaussian PT symmetric media (modulation depth P, modulation factor ω, and gain/loss factor W0) and the characteristic parameters of Airy-Gaussian beams (truncation factor a, distribution factor χ0) on propagation characteristics of Airy-Gaussian beams are examined in detail. The results demonstrate that the Airy-Gaussian beams can produce oscillating solitons and transmit steadily in Gaussian PT symmetric media. The soliton strength increases with the increase of P, W0, and a, and decreases with the increase of ω. The oscillation period decreases with the increase of P and ω and increases with the increase of W0. When χ0 increases, when 0<χ0<0.55, the peak intensity of the soliton does not change obviously; when χ0>0.55, the peak intensity of the soliton decreases rapidly. This research can offer a theoretical foundation for the use of soliton transmission in complicated heterogeneous media and all-optical control.
Laser & Optoelectronics Progress
- Publication Date: Aug. 10, 2023
- Vol. 60, Issue 15, 1519001 (2023)
Comparison of Calculation Methods for Chaotic Laser in Semiconductor Laser System
Xiangshuai Guo, Shangqi Kuang, and Yuling Feng
The dynamic equation of the semiconductor laser system is a critical theoretical basis for investigating chaotic lasers, whose calculation accuracy directly determines the simulation reliability of the chaotic laser generated by the system. In this study, different semiconductor laser systems are evaluated and compared based on the two widely used methods of photoelectric field decomposition: amplitude-phase decomposition and real-imaginary part solution. The comparison shows that the computational results of both methods have a minimal difference in the case of low complexity of output light, but a significant difference exists in the case of high complexity. Furthermore, the numerical simulation of the photoelectric field using the real-imaginary part solution has higher precision and is more suitable than the amplitude-phase decomposition for analyzing semiconductor laser systems that generate chaotic lasers with higher complexity. The dynamic equation of the semiconductor laser system is a critical theoretical basis for investigating chaotic lasers, whose calculation accuracy directly determines the simulation reliability of the chaotic laser generated by the system. In this study, different semiconductor laser systems are evaluated and compared based on the two widely used methods of photoelectric field decomposition: amplitude-phase decomposition and real-imaginary part solution. The comparison shows that the computational results of both methods have a minimal difference in the case of low complexity of output light, but a significant difference exists in the case of high complexity. Furthermore, the numerical simulation of the photoelectric field using the real-imaginary part solution has higher precision and is more suitable than the amplitude-phase decomposition for analyzing semiconductor laser systems that generate chaotic lasers with higher complexity.
Laser & Optoelectronics Progress
- Publication Date: Jan. 10, 2023
- Vol. 60, Issue 1, 0119001 (2023)
Influence of Uniform Unmagnetized Plasma on Electromagnetic Wave Absorption Characteristics
Jie Zhang, Shanchao Zhao, Bing Han, and Guodong Zhang
Based on the "blackout", the physical model of "free space-plasma layer-free space" is established. On the basis of this model, the analytical method is used to simulate and study the relationship between plasma absorption rate and electromagnetic wave frequency under the premise of different thickness plasma layer. The absorption of left-handed and right-handed circularly polarized waves by plasma layer and the one-way attenuation of electromagnetic waves in plasma were studied by changing the electron density, external magnetic field intensity and electron collision frequency, respectively. The results show that the absorption characteristics and one-way attenuation of electromagnetic waves by plasma change with the change of plasma layer thickness, electron density, external magnetic field strength, and electron collision frequency. The simulation results can be used as a reference for reducing the absorption rate of plasma layer and alleviating the problem of the "blackout". Based on the "blackout", the physical model of "free space-plasma layer-free space" is established. On the basis of this model, the analytical method is used to simulate and study the relationship between plasma absorption rate and electromagnetic wave frequency under the premise of different thickness plasma layer. The absorption of left-handed and right-handed circularly polarized waves by plasma layer and the one-way attenuation of electromagnetic waves in plasma were studied by changing the electron density, external magnetic field intensity and electron collision frequency, respectively. The results show that the absorption characteristics and one-way attenuation of electromagnetic waves by plasma change with the change of plasma layer thickness, electron density, external magnetic field strength, and electron collision frequency. The simulation results can be used as a reference for reducing the absorption rate of plasma layer and alleviating the problem of the "blackout".
Laser & Optoelectronics Progress
- Publication Date: Feb. 10, 2022
- Vol. 59, Issue 3, 0319001 (2022)
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