Author Affiliations
Abstract
1 Information Materials and Intelligent Sensing Laboratory of Anhui Province, Key Laboratory of Opto-Electronic Information Acquisition and Manipulation of Ministry of Education, School of Physics and Opto-electronics Engineering, Anhui University, Hefei 230601, China
2 School of Instrument Science and Opto-electronics Engineering, Laboratory of Optical Fibers and Micro-nano Photonics, Hefei University of Technology, Hefei 230009, China
3 School of Opto-electronic Engineering, Zaozhuang University, Zaozhuang 277160, China
Random lasers are a type of lasers that lack typical resonator structures, offering benefits such as easy integration, low cost, and low spatial coherence. These features make them popular for speckle-free imaging and random number generation. However, due to their high threshold and phase instability, the production of picosecond random lasers has still been a challenge. In this work, we have developed three dyes incorporating polymer optical fibers doped with various scattering nanoparticles to produce short-pulsed random fiber lasers. Notably, stable picosecond random laser emission lasting 600 ps is observed at a low pump energy of 50 µJ, indicating the gain-switching mechanism. Population inversion and gain undergo an abrupt surge as the intensity of the continuously pumped light nears the threshold level. When the intensity of the continuously pumped light reaches a specific value, the number of inversion populations in the “scattering cavity” surpasses the threshold rapidly. Simulation results based on a model that considers power-dependent gain saturation confirmed the above phenomenon. This research helps expand the understanding of the dynamics behind random medium-stimulated emission in random lasers and opens up possibilities for mode locking in these systems.
random laser polymer optical fiber gain-switched laser picosecond pulse Chinese Optics Letters
2024, 22(4): 040603
本文利用等离子体辅助分子束外延(PA-MBE)系统, 对常规连续外延生长和金属调制外延(MME)生长AlN薄膜进行研究。研究发现: 常规连续外延方法生长模式不易控制, 容易出现过度富Al和富N模式生长, 而且微富Al模式生长还会出现一些凹坑, 表面形貌较粗糙; 然而利用MME方法生长AlN薄膜, 通过精准调控Al源和N源快门打开、关闭时间, 可以获得形貌较好的AlN薄膜。通过调整优化获得的MME方案为: 首先Al源快门打开30 s, 然后Al源和N源快门打开60 s, 最后单独打开N源快门72 s; 单一周期内, Al源快门打开时间与N源快门打开时间比例为0.7。以上述方案为一个周期进行循环生长40个周期, 可获得粗糙度低至0.3 nm(2 μm×2 μm), 几乎无凹坑的AlN薄膜。
金属调制 分子束外延 外延生长 氮化铝 粗糙度 metal modulation molecular beam epitaxy epitaxial growth aluminum nitride roughness
实现电学性能优良的高Al组分AlGaN外延层是制备深紫外光电器件最重要的环节之一。本工作利用分子束外延(MBE)技术, 基于周期热脱附的生长方式, 通过改变Al源供应量调控Al组分, 并用Si进行n型掺杂, 在AlN/蓝宝石衬底上得到了系列高Al组分的Si-AlxGa1-xN外延层(x>0.60)。对外延层相关物理性质进行了表征测试, 结果表明, 外延层Al组分与生长过程中Al束流大小呈现线性关系, 这为制备精确Al组分的AlGaN外延层奠定了基础。AFM结果表明, 高Al组分AlGaN外延层的表面形貌强烈依赖于Ga的供应量, 在生长过程中提高Ga束流可以显著降低外延层的粗糙度。基于范德堡法测量Si-AlGaN外延层电学性能, 证实其载流子特性良好, 其中 Al组分为0.93的样品室温下自由电子浓度、电子迁移率和电阻率分别达到了8.9×1018 cm-3和3.8 cm2·V-1·s-1和0.18 Ω·cm。
高Al组分AlGaN 分子束外延 Si掺杂 载流子特性 周期热脱附 high Al-content AlGaN molecular beam epitaxy Si doping carrier property periodic thermal desorption
Author Affiliations
Abstract
1 State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics (XIOPM), Chinese Academy of Sciences (CAS), Xi’an 710119, China
2 University of Chinese Academy of Sciences, Beijing 100049, China
3 e-mail: wfuzhang@opt.ac.cn
We investigate frequency-comb generation in normal dispersion silicon microresonators from the near-infrared to mid-infrared wavelength range in the presence of multiphoton absorption and free-carrier effects. It is found that parametric oscillation is inhibited in the telecom wavelength range resulting from strong two-photon absorption. On the contrary, beyond the wavelength of 2200 nm, where three- and four-photon absorption are less detrimental, a comb can be generated with moderate pump power, or free-carriers are swept out by a positive-intrinsic-negative structure. In the temporal domain, the generated combs correspond to flat-top pulses, and the pulse duration can be easily controlled by varying the laser detuning. The reported comb generation process shows a high conversion efficiency compared with anomalous dispersion regime, which can guide and promote comb formation in materials with normal dispersion. As the comb spectra cover the mid-infrared wavelength range, they can find applications in comb-based radiofrequency photonic filters and mid-infrared spectroscopy.
Nonlinear optics, four-wave mixing Nonlinear optics, integrated optics Parametric oscillators and amplifiers Microcavities Photonics Research
2018, 6(4): 04000238
中国电子科技集团公司 第10 研究所,四川 成都 610036
为了有效模拟和分析雷达目标回波特点,提出了一种数字仿真方法来建模和设计雷达目标回波。通过对高分辨单脉冲雷达的原理分析,设计雷达目标回波仿真系统框架,将系统分解成多个模块,针对每个模块建立相应的数字模型,并利用计算机软件实现,仿真表明该方法能有效建立雷达目标三通道一维距离像回波,并对后续单脉冲跟踪数据处理的研究具有指导意义。
高分辨 单脉冲雷达 距离像回波 建模仿真 high resolution monopulse radar range profile echo modeling and simulation 太赫兹科学与电子信息学报
2016, 14(2): 186