Under the condition of combined effects of group--velocitydispersion and self- phase modulation, the step Fourier method isused to simulate the propagation of initial chirped super-Gaussianpulses inside fiber. The ini...Under the condition of combined effects of group--velocitydispersion and self- phase modulation, the step Fourier method isused to simulate the propagation of initial chirped super-Gaussianpulses inside fiber. The initial chirp influences the shapes of superGaussian pulses in propagation process, and positive and negativechirps have different effects. For the existing of initial chirp, thesplits of pulses and the spreading speed move ahead and increase.When the amplitude of super-Gaussian pulses increases by 1.4 times,in the range of │C│<1.5, pulses can keep good shapes along theirpropagation distance.展开更多
The molecular orientation created by laser fields is important for steering chemical reactions. In this paper, we propose a theoretical scheme to manipulate field-free molecular orientation by using an intense super-G...The molecular orientation created by laser fields is important for steering chemical reactions. In this paper, we propose a theoretical scheme to manipulate field-free molecular orientation by using an intense super-Gaussian laser pulse and a time-delayed terahertz half-cycle pulse(THz HCP). It is shown that the degree of field-free orientation can be doubled by the combined pulse with respect to the super-Gaussian pulse or THz HCP alone. Moreover, different laser intensities, carrier envelop phases, shape parameters, and time delays have great influence on the positive and negative orientations, with other conditions unchanged. Furthermore, it is indicated that the maximum degree and direction of molecular orientation can be precisely controlled by half of the duration of the super-Gaussian pulse. Finally, by adjusting the laser parameters of the super-Gaussian laser pulse and THz HCP, the optimal results of negative orientation and corresponding rotational populations are obtained at different temperatures of the molecular system.展开更多
【目的】高光谱图像因其丰富的光谱信息而备受关注,然而,由于成像硬件条件的限制,通常很难直接获得高空间分辨率的高光谱图像。为了提高分辨率,将高光谱图像与从同一场景采集的高空间分辨率的多光谱图像融合是一种经济有效的方法。然而...【目的】高光谱图像因其丰富的光谱信息而备受关注,然而,由于成像硬件条件的限制,通常很难直接获得高空间分辨率的高光谱图像。为了提高分辨率,将高光谱图像与从同一场景采集的高空间分辨率的多光谱图像融合是一种经济有效的方法。然而,现有的大多数基于深度学习的方法未充分挖掘图像间空间和光谱相关性,导致融合性能受限。【方法】本文提出了一种结合图像去噪、光谱特征与空间特征增强的高光谱图像超分辨率融合方法。首先,通过使用不同标准差的高斯模糊核对高光谱与多光谱图像进行高斯模糊处理,有效减少这2种模态图像中包含的噪声。其次,为了提高融合图像的精确度,在利用不同模态图像间光谱和空间相关性重建高分辨率图像时,分别引入通道注意力和空间注意力,利用增强图像关键信息的方式获得不同模态间更好的空间和光谱相关性。最后,利用增强的空间和光谱相关性,将映射得到的高分辨率图像特征聚合起来,重建出高空间分辨率的高光谱图像。【结果】在ZY-m和Chikusei数据集上融合结果的PSNR分别为53.586和53.738,在ZY-m数据集上较次优方法空谱解耦互引导网络(Spatial-Spectral Unfolding Network with Mutual Guidance,SMGU-Net)提高2.8%,在Chikusei数据集上较次优方法带有双条件调制模块的扩散模型(Diffusion Model with two Conditional Modulation Modules,DDIF)提高1.70%;SAM值达到0.006和0.018,在ZY-m数据集上较次优方法 SMGU-Net降低14.28%,在Chikusei数据集上较次优方法 DDIF降低5.26%。【结论】本文方法具有良好的光谱保真度和空间细节增强能力,为高光谱图像的超分辨率提供了一种有效技术方案,展示了其在国土资源勘查、环境监测等领域的良好应用潜力。展开更多
Relationship between the initial chirp of super-Gaussian pulse and dispersion and nonlinearity effects of a single-mode fiber in the optical communication system using midway optical phase conjugation is analyzed. The...Relationship between the initial chirp of super-Gaussian pulse and dispersion and nonlinearity effects of a single-mode fiber in the optical communication system using midway optical phase conjugation is analyzed. The results of numerical simulations are useful for improving compensation for pulse distortion.展开更多
A high-energy pulsed vacuum ultraviolet(VUV) solid-state laser at 177 nm with high peak power by the sixth harmonic of a neodymium-doped yttrium aluminum garnet(Nd:YAG) amplifier in a KBe_(2)BO_(3)F_(2) prism-coupled ...A high-energy pulsed vacuum ultraviolet(VUV) solid-state laser at 177 nm with high peak power by the sixth harmonic of a neodymium-doped yttrium aluminum garnet(Nd:YAG) amplifier in a KBe_(2)BO_(3)F_(2) prism-coupled device was demonstrated. The ultraviolet(UV) pump laser is a 352 ps pulsed, spatial top-hat super-Gaussian beam at 355 nm.A high energy of a 7.12 mJ VUV laser at 177 nm is obtained with a pulse width of 255 ps, indicating a peak power of 28 MW, and the conversion efficiency is 9.42% from 355 to 177 nm. The measured results fitted well with the theoretical prediction. It is the highest pulse energy and highest peak power ever reported in the VUV range for any solid-state lasers.The high-energy, high-peak-power, and high-spatial-uniformity VUV laser is of great interest for ultra-fine machining and particle-size measurements using UV in-line Fraunhofer holography diagnostics.展开更多
文摘Under the condition of combined effects of group--velocitydispersion and self- phase modulation, the step Fourier method isused to simulate the propagation of initial chirped super-Gaussianpulses inside fiber. The initial chirp influences the shapes of superGaussian pulses in propagation process, and positive and negativechirps have different effects. For the existing of initial chirp, thesplits of pulses and the spreading speed move ahead and increase.When the amplitude of super-Gaussian pulses increases by 1.4 times,in the range of │C│<1.5, pulses can keep good shapes along theirpropagation distance.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674198 and 11874241)the Taishan Scholar Project of Shandong Province,China
文摘The molecular orientation created by laser fields is important for steering chemical reactions. In this paper, we propose a theoretical scheme to manipulate field-free molecular orientation by using an intense super-Gaussian laser pulse and a time-delayed terahertz half-cycle pulse(THz HCP). It is shown that the degree of field-free orientation can be doubled by the combined pulse with respect to the super-Gaussian pulse or THz HCP alone. Moreover, different laser intensities, carrier envelop phases, shape parameters, and time delays have great influence on the positive and negative orientations, with other conditions unchanged. Furthermore, it is indicated that the maximum degree and direction of molecular orientation can be precisely controlled by half of the duration of the super-Gaussian pulse. Finally, by adjusting the laser parameters of the super-Gaussian laser pulse and THz HCP, the optimal results of negative orientation and corresponding rotational populations are obtained at different temperatures of the molecular system.
文摘【目的】高光谱图像因其丰富的光谱信息而备受关注,然而,由于成像硬件条件的限制,通常很难直接获得高空间分辨率的高光谱图像。为了提高分辨率,将高光谱图像与从同一场景采集的高空间分辨率的多光谱图像融合是一种经济有效的方法。然而,现有的大多数基于深度学习的方法未充分挖掘图像间空间和光谱相关性,导致融合性能受限。【方法】本文提出了一种结合图像去噪、光谱特征与空间特征增强的高光谱图像超分辨率融合方法。首先,通过使用不同标准差的高斯模糊核对高光谱与多光谱图像进行高斯模糊处理,有效减少这2种模态图像中包含的噪声。其次,为了提高融合图像的精确度,在利用不同模态图像间光谱和空间相关性重建高分辨率图像时,分别引入通道注意力和空间注意力,利用增强图像关键信息的方式获得不同模态间更好的空间和光谱相关性。最后,利用增强的空间和光谱相关性,将映射得到的高分辨率图像特征聚合起来,重建出高空间分辨率的高光谱图像。【结果】在ZY-m和Chikusei数据集上融合结果的PSNR分别为53.586和53.738,在ZY-m数据集上较次优方法空谱解耦互引导网络(Spatial-Spectral Unfolding Network with Mutual Guidance,SMGU-Net)提高2.8%,在Chikusei数据集上较次优方法带有双条件调制模块的扩散模型(Diffusion Model with two Conditional Modulation Modules,DDIF)提高1.70%;SAM值达到0.006和0.018,在ZY-m数据集上较次优方法 SMGU-Net降低14.28%,在Chikusei数据集上较次优方法 DDIF降低5.26%。【结论】本文方法具有良好的光谱保真度和空间细节增强能力,为高光谱图像的超分辨率提供了一种有效技术方案,展示了其在国土资源勘查、环境监测等领域的良好应用潜力。
文摘Relationship between the initial chirp of super-Gaussian pulse and dispersion and nonlinearity effects of a single-mode fiber in the optical communication system using midway optical phase conjugation is analyzed. The results of numerical simulations are useful for improving compensation for pulse distortion.
基金supported by the National Key Research and Development Program of China(No.2023YFB3610601)the International Partnership Program for Grand Challenges of the Chinese Academy of Sciences(No.174GJHZ2022016GC)the National Special Program for High-level Talents Science and Technology(No.SQ2022RA24910010)
文摘A high-energy pulsed vacuum ultraviolet(VUV) solid-state laser at 177 nm with high peak power by the sixth harmonic of a neodymium-doped yttrium aluminum garnet(Nd:YAG) amplifier in a KBe_(2)BO_(3)F_(2) prism-coupled device was demonstrated. The ultraviolet(UV) pump laser is a 352 ps pulsed, spatial top-hat super-Gaussian beam at 355 nm.A high energy of a 7.12 mJ VUV laser at 177 nm is obtained with a pulse width of 255 ps, indicating a peak power of 28 MW, and the conversion efficiency is 9.42% from 355 to 177 nm. The measured results fitted well with the theoretical prediction. It is the highest pulse energy and highest peak power ever reported in the VUV range for any solid-state lasers.The high-energy, high-peak-power, and high-spatial-uniformity VUV laser is of great interest for ultra-fine machining and particle-size measurements using UV in-line Fraunhofer holography diagnostics.
