Author Affiliations
Abstract
1 Key Laboratory for Laser Plasma, Shanghai Jiao Tong University, Shanghai 200240, China
2 Key Laboratory of Micro and Nano Photonic Structures, Fudan University, Shanghai 200433, China
3 Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai 200240, China
We propose a spatially chirped quasi-phase-matching (QPM) scheme that enables ultrabroadband second-harmonic-generation (SHG) by using a fan-out QPM grating to frequency-convert a spatially chirped fundamental wave. A “zero-dispersion” 4f system maps the spectral contents of ultrabroadband fundamental onto different spatial coordinates in the Fourier plane, where the fundamental is quasi-monochromatic locally in picosecond duration, fundamentally canceling high-order phase mismatch. A fan-out QPM grating characterized by a linear variation of the poling period along the transverse direction exactly supports the QPM of the spatially chirped beam. We theoretically demonstrate the SHG of an 810-nm, 12.1-fs pulse into a 405-nm, 10.2-fs pulse with a conversion efficiency of 77%.
nonlinear optics second-harmonic generation few-cycle pulse Chinese Optics Letters
2024, 22(1): 011901
Author Affiliations
Abstract
1 Shanghai Engineering Research Center of Ultra-precision Optical Manufacturing, Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China
2 Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China
3 Key Laboratory for Laser Plasmas (Ministry of Education), Collaborative Innovation Center of IFSA (CICIFSA), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
Quasi-parametric chirped-pulse amplification (QPCPA) can improve the signal amplification efficiency and stability by inhibiting the back-conversion, in which the idler absorption plays a critical role. This Letter theoretically studies the impacts of idler absorption on the QPCPA performance in both the small-signal and saturation regimes. We demonstrate that there exists an optimal idler absorption that enables the achievement of maximum pump depletion within a minimum crystal length. To overcome the reduction in small-signal gain induced by idler absorption, the configuration of gradient idler absorption is proposed and demonstrated as a superior alternative to constant idler absorption. The results provide guidelines to the design of state-of-the-art QPCPA lasers.
190.4410 Nonlinear optics, parametric processes Chinese Optics Letters
2018, 16(12): 121901
1 复旦大学 光科学与工程系, 上海 200433
2 上海秉睿实业有限公司, 上海 201800
激光雷达是一种精确的遥感风速测量方法。介绍了一种全光纤相干多普勒激光测风雷达, 系统所有光学元件之间采用光纤连接, 结构简单, 调节方便。首先, 使用该激光雷达系统的数据处理方法, 对计算机模拟的探测器表面的中频多普勒频移信号进行测量, 噪声的功率越大, 信噪比越小, 误差也越大。其次, 使用该激光雷达系统对硬靶目标进行了速度测量, 测量结果与标准值比较一致, 最大误差的绝对值不超过0.046 m/s。最后, 使用该激光雷达系统对水蒸气目标进行了速度测量, 测量结果与标准值基本相近, 最大误差的绝对值小于等于0.925 m/s。仿真和实际实验的测量结果均证明了该激光雷达系统测量结果的准确性和稳定性。
激光雷达 全光纤 多普勒频移 测风 light detection and ranging(LiDAR) all-fiber Doppler shift wind measurement 红外与激光工程
2016, 45(s1): S130001
Author Affiliations
Abstract
1 Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China
2 School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou 221116, China
3 Jiangsu Collaborative Innovation Center of Advanced Laser Technology and Emerging Industry, Jiangsu Normal University, Xuzhou 221116, China
We report on a widely tunable, narrow linewidth operation of a Tm:YAG ceramic laser. A volume Bragg grating is used in the cavity as a folding mirror for wavelength selection. The wavelength is tuned from 1956.2 to 1995 nm, leading to a total tuning range of 38.7 nm. The linewidth is around 0.1 nm over the whole tuning range. A maximum output power of 1.51 W at 1990.5 nm is achieved at 37.8 W absorbed pump power. Different saturation behaviors are observed in the laser performances at different wavelengths.
140.3600 Lasers, tunable 140.3580 Lasers, solid-state 050.7330 Volume gratings Chinese Optics Letters
2015, 13(6): 061404
1 复旦大学光科学与工程系， 上海 200433
2 上海交通大学物理系激光等离子体教育部重点实验室， 上海 200240
脉冲信噪比是高强度激光的一个重要技术参数，反映了激光系统的技术水平。由于高强度激光的重复频率很低甚至单次运行，必须开发实时的单次测量技术。当前，信噪比单次测量技术非常匮乏，技术难度远高于扫描测量方式。本课题组提出了可实现大窗口、高动态范围测量的技术方案，形成了系列创新技术，通过关键技术集成研制了实用化的测量样机。原理性验证实验考核了技术方案的可行性、可靠性和主要技术性能，已实现动态范围约为109、时间窗口50～100 ps和分辨率0.5～1 ps的信噪比单次测量，且在时间窗口内无测量引入的假信号。脉冲信噪比单次测量样机已成功应用于我国的拍瓦激光装置。
测量 单次测量 脉冲信噪比 准相位匹配 长波长取样 光纤阵列 激光与光电子学进展
2013, 50(8): 080008
1 复旦大学光科学与工程系, 上海 200433
2 华南师范大学 光子信息技术广东省高校重点实验室, 广东 广州 510631
介绍了由相速度分布诱导的差频光图样演化过程。由于相速度的非均匀分布, 诸如圆环型、弯月型的图样均会在差频过程中出现。由不同相位失配情况下差频光分布曲线的交叉点可得知超光速和亚光速区域的分界线。
光学混频 相速度 聚焦光束
1 湖南大学计算机与通信学院,湖南长沙 410012
2 复旦大学光科学与工程系, 上海 200433
讨论了若干利用二阶非线性效应的飞秒激光技术研究进展。基于传统的钛宝石飞秒激光器,提出了可产生稳定的1μm波段可调谐飞秒激光的新型注入式飞秒光参量放大(OPA)系统。结合相位匹配折返原理,用部分氘化KDP晶体作为二阶非线性介质,实现了对20nm带宽的1mm波段飞秒激光的高效宽带倍频,倍频效率达到55%。最后介绍了具有脉冲扩展功能的时间望远镜系统。
飞秒激光 二阶非线性 光参量放大 倍频 时间望远镜
1 复旦大学光科学与工程系先进光子学材料与器件国家重点实验室, 上海 200433
2 中国科学院上海光学精密机械研究所, 上海 201800
对B积分(自聚焦)的有效抑制和控制是高能激光系统发展过程中的一个焦点问题.传统的B积分控制技术(空间滤波器)在一定程度上提高了光束质量,但是随着激光功率的不断增大,空间滤波技术受到诸多因素限制,已经不能满足要求,因此还需发展新的B积分控制技术.基于非线性倍频过程的二阶级联非线性可等效于三阶非线性,它的符号可控(允许为负),量值可变且很大,并可消除双光子吸收.级联非线性实际上提供了一个新的自由度,它可以产生有用的非线性相移.初步实验表明,利用级联非线性产生的负非线性相移,在一定程度上可以补偿强激光束在非线性传输过程中积累的B积分,具有很好的应用前景.
级联非线性 光束畸变 补偿
1 复旦大学物理系, 三束材料改性国家重点实验室复旦大学分部, 上海 200433
2 复旦大学高分子科学系, 上海 200433
在532 nm波长处测量了共轭高聚物PPQ薄膜的三阶光学非线性参数, 发现其较强的非线性(双光子)吸收系数β≈0.59 cm/MW。 其非线性折射率系数n2≈9.5×10-10 esu, 认为这是双光子激发的纯电子响应。 并对材料的品质因素进行了评估。
共轭高聚物 超快光学非线性 Z-扫描
