共查询到15条相似文献,搜索用时 78 毫秒
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应用粒子模拟软件对设计的二次谐波三腔回旋速调管放大器进行了数值模拟。分析讨论了二次谐波注-波互作用过程中电子群聚的物理图景和特点,并研究了电子注电流和归一化引导中心半径对电子注-波互作用效率的影响。模拟结果表明,本文设计的二次谐波三腔回旋速调管放大器在35GHz频率可获得约293kW的峰值输出功率和约28%的电子效率。 相似文献
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报道了一种在光纤中激发二次谐波振荡(SHG)的简单方法:利用紫外脉冲激光在载氢后的高浓度铒、镱共掺的光纤上刻制布拉格光栅。从而打破了石英光纤二阶极化率为零的固有限制,形成了极大的永久的二阶极化率,周期性的结构辅助实现了相位的匹配。在实验中,利用波长为980nm的半导体激光器(LD)抽运该光纤光栅,在只有几毫瓦的抽运功率下,便观察到了显著的蓝绿光辐射,而且强度随抽运功率的增加而增加。在显微镜下对光纤光栅发光现象进行了观测并拍摄了数码相片,在相片中观测到光纤光栅纤芯处的蓝绿光辐射,而非光栅区没有发光现象,同时观测到了紫外光辐射。 相似文献
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利用阶梯分段准相位匹配结构实现了基于级联倍频+差频效应的单通/双通宽带波长转换.对于固定的晶体长度,通过增加阶梯段数并合理设计准相位匹配结构参数,可以同时获得高转换效率、大转换带宽和高平坦性.当晶体长度为3 cm时,在保证平坦度低于0.2 dB的前提下,单通构型波长转换器的转换带宽和最大转换效率可分别达到177 nm和-9.94 dB,而双通构型的分别为170 nm和-4.15 dB.最后对基于阶梯分段准相位匹配结构的波长转换器与基于正弦啁啾光学超晶格和分段光栅结构的波长转换器的特性进行了对比分析,结果显示阶梯分段结构具有良好的综合特性. 相似文献
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本文报道向列相液晶在电场诱导下以及经液晶池界面化学处理后,获得了垂直结构的体系的位相匹配且产生了二次谐波.首次测定该液晶的非线性系数张量的矩阵各分量,并给出诱导场强与谐波强度的关系. 相似文献
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P.Kumaresan 《中国电子科技》2010,8(1):43-45
Most irradiation studies in the hydrogen bonded ferroelectrics have been concentrated on the transient defects induced by ionising radiation,such as ultraviolet(UV) light,where the defects are closely related to the optical properties.But heavy ion beam irradiation effects have rarely been studied.The structural,optical,and non-linear optical properties of the doped crystals were analyzed with the characterization studies,such as powder XRD,UV-Visible and second harmonic generation(SHG) measurements,respect... 相似文献
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等离子体开关在TEA CO2激光倍频中的应用 总被引:2,自引:1,他引:2
简要分析了脉冲整形对于TEA CO2激光倍频实验的重要性和必要性。目前,获得短脉冲的激光脉冲整形技术中,等离子体开关结构简单,而且脉冲整形效果好,是获得高质量短脉冲比较好的方法。设计了利用激光触发气体击穿产生等离子体的方式进行脉冲整形的等离子体开关,并利用电磁波在等离子体中的反射和传播对其工作原理进行了说明。利用自行研制的等离子体开关进行了TEA CO2激光脉冲整形实验,将主峰半高全宽(FWHM)60 ns,带有长达数百纳秒的氮气拖尾的TEA CO2激光脉冲斩去拖尾、整形,得到了FWHM 30 ns的窄脉冲。在双块AgGaSe2晶体(长分别为11.7mm和19.5mm)倍频实验光路图中加入等离子体开关所得倍频转换效率达12.9%,比起未加等离子体开关时最高转换效率2%有明显的增加。 相似文献
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Gitanjali Kolhatkar Mischa Nicklaus Azza Hadj Youssef Cristian Cojocaru Maxime Rivard Alexandre Merlen Franois Lgar Andreas Ruediger 《Advanced functional materials》2019,29(36)
Strain gradients induced by nanoindentations in bulk undoped strontium titanate (SrTiO3) are investigated. After indenting a 850 nm deep pattern on the SrTiO3 surface with a 8 GPa hardness and an 83 GPa indentation modulus by a Berkovich tip, the resulting deformation patterns are imaged by Raman spectroscopy and by second harmonic generation microscopy. Cross‐shaped compressively stressed regions along the cubic SrTiO3 primary slip planes are observed. These zones relax toward the unstrained bulk material through localized strain gradients on a length scale of several microns. Second harmonic tomography reveals the reduction of the crystal's centrosymmetry in the vicinity of the crosslike features due to a strain gradient. These results indicate the appearance of flexoelectricity following the nanoindentation process due to the creation of an inhomogeneous strain. 相似文献
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Xin-Yu Li Qi Wei Chun-Li Hu Jie Pan Bing-Xuan Li Zhen-Zhen Xue Xiao-Yu Li Jin-Hua Li Jiang-Gao Mao Guo-Ming Wang 《Advanced functional materials》2023,33(3):2210718
Trigonal planar units with large polarizability anisotropy and high physicochemical stability are ideal structural units for exploring nonlinear optical (NLO) materials. Integrating the merits of two types of triangular-like moieties, a family of second-order NLO-active hybrid halides, MATX (X = Cl (1), Br ( 2 ), and I ( 3 )), are achieved. MATX crystallizes in a nonpolar space group of 2c but exhibits the optimal spatial arrangement and superior NLO performance. The low coordination planar trigonal AgX3 units enable segregation in layers of the three-winged propeller-like Me3TPA units. All of the layers are packed in a perfect parallel fashion, making the functional materials exhibit superior NLO performances, including the phase matchable behavior with strong SHG responses (6.2/ 1 , 6.5/ 2, and 7.6/ 3 times that of potassium dihydrogen phosphate), large birefringence (0.232/ 1 , 0.252/ 2 and 0.260/ 3 at 1064 nm), high laser damage threshold, wide transparent window, and easiness of crystal growth. The first-principles calculations reveal that the coexistence of strong linear and nonlinear optical properties are ascribed to the synergistic effect of the trigonal moieties. This study points out a useful path for the rational design of excellent NLO materials. 相似文献
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本文提出一种基于第二代bandelets,并结合多层阈值和自适应Wiener滤波的图像去噪方法.第二代bandelets能充分利用图像内在的几何正则性,自适应获得图像的最优表示;多层阈值符合小波多尺度域的系数统计特性;维纳滤波可以有效去除阈值去噪带来的纹理效应.实验结果表明:该去噪方法与基于小波变换的方法相比,作用于含有加性高斯白噪声的光学图像时,避免了小波变换带来的边界的振铃效应,并在峰值信噪比上有一定的改善;作用于合成孔径雷达图像中的相干斑抑制时,不论从视觉效果还是等效视数和比值图等衡量指标上都取得了较好的效果. 相似文献