1 天津大学精密仪器与光电子工程学院超快激光实验室，天津 300072
2 天津大学佐治亚理工深圳学院，广东 深圳 518055
基于掺Yb3+光纤和掺Yb3+晶体的飞秒激光器输出的飞秒激光脉冲具有较高的脉冲能量和平均功率，被广泛应用于科研和工业生产；但受Yb3+增益介质增益带宽的限制，输出脉冲宽度很难小于300 fs。利用飞秒激光脉冲在多层薄板中的自相位调制效应，分别对基于掺Yb3+光纤和掺Yb3+晶体的飞秒激光器输出的飞秒激光脉冲进行非线性压缩。通过优化非线性压缩装置的各项参数，实现了对低能量、窄脉宽和高能量、宽脉宽脉冲的非线性压缩，分别获得了脉冲能量为64 μJ、脉冲宽度为42 fs和脉冲能量为315 μJ、脉冲宽度为79 fs的飞秒激光脉冲输出，第一级非线性压缩效率均超过80%，整体压缩效率分别为53%和65%。
激光器 飞秒激光脉冲 自相位调制 非线性压缩 光谱展宽
Author Affiliations
Abstract
1 Ultrafast Laser Laboratory, Key Laboratory of Opto-electronic Information Technology (Ministry of Education), School of Precision Instruments and Opto-electronics Engineering, Tianjin University, Tianjin 300072, China
2 Georgia Tech Shenzhen Institute, Tianjin University, Shenzhen 518055, China
3 Optoelectronic Detection and Processing Laboratory, School of Electronic Engineering, Tianjin University of Technology and Education, Tianjin 300222, China
High-order dispersion introduced by Gires–Tournois interferometer mirrors usually causes spectral sidebands in the near-zero dispersion region of mode-locked fiber lasers. Here, we demonstrate a sideband-free Yb-doped mode-locked fiber laser with dispersion-compensating Gires–Tournois interferometer mirrors. Both the simulation and the experiment demonstrate that the wavelength and energy of the sidebands can be tuned by changing the transmission coefficient of the output mirror, the pump power, and the ratio of the net cavity dispersion to the net third-order dispersion in the cavity. By optimizing these three parameters, the laser can generate a sideband-free, Gaussian-shaped spectrum with a 13.56-nm bandwidth at net cavity dispersion, which corresponds to a 153-fs pulse duration.
fiber laser dispersion compensation sideband suppression Chinese Optics Letters
2023, 21(6): 061401
1 中车株洲电力机车有限公司，湖南 株洲 412001
2 华中科技大学 材料科学与工程学院，湖北 武汉 430074
针对轨道交通车辆车体铝合金型材焊接同步激光清洗，开展了相关工艺、测试与应用技术研究。通过工艺研究得出铝合金氧化膜激光清洗工艺窗口，建立了匹配不同焊接速度的激光清洗参数预测模型，并分析了激光清洗对铝合金表面氧化膜的影响；针对实际工况，设计了激光清洗-电弧焊接同步清焊一体化装置，并开展焊接同步激光清洗工艺验证，实现了焊前高质高效去除氧化膜；通过分析焊接接头力学性能，检测焊缝缺陷，观测焊接接头截面微观组织，评判焊接同步激光清洗焊缝质量。研究表明，采用200 W脉冲激光，清洗速度0.5~1.1 m/min可调的情况下，可以实现线宽45 mm的焊接同步氧化膜的有效清洗，经激光清洗后，原生氧化膜被完全去除，且可避免再生氧化膜的影响。经激光清洗后的焊接接头剪切强度及应变相较未处理的接头分别提升了26.4%和9.98%，较人工打磨后的接头强度分别提升了3.53%和1.43%，焊缝中心组织主要由α基体和β （Mg2Al3）相组成，焊接性能满足轨道交通车辆车体制造要求，可有效替代人工打磨。
铝合金 激光清洗 氧化膜 清焊一体 aluminum alloy laser cleaning oxide film integrated laser cleaning and welding 红外与激光工程
2023, 52(2): 20220534
Author Affiliations
Abstract
Department of Mechanical and Energy Engineering, Southern University of Science and Technology, Shenzhen 518055, People’s Republic of China
Electrochemical jet machining (EJM) encounters significant challenges in the microstructuring of chemically inert and passivating materials because an oxide layer is easily formed on the material surface, preventing the progress of electrochemical dissolution. This research demonstrates for the first time a jet-electrolytic plasma micromachining (Jet-EPM) method to overcome this problem. Specifically, an electrolytic plasma is intentionally induced at the jet-material contact area by applying a potential high enough to surmount the surface boundary layer (such as a passive film or gas bubble) and enable material removal. Compared to traditional EJM, introducing plasma in the electrochemical jet system leads to considerable differences in machining performance due to the inclusion of plasma reactions. In this work, the implementation of Jet-EPM for fabricating microstructures in the semiconductor material 4H-SiC is demonstrated, and the machining principle and characteristics of Jet-EPM, including critical parameters and process windows, are comprehensively investigated. Theoretical modeling and experiments have elucidated the mechanisms of plasma ignition/evolution and the corresponding material removal, showing the strong potential of Jet-EPM for micromachining chemically resistant materials. The present study considerably augments the range of materials available for processing by the electrochemical jet technique.
electrochemical jet machining electrolytic plasma passivation oxide film breakdown material removal mechanism International Journal of Extreme Manufacturing
2022, 4(4): 045101
重庆邮电大学 光电工程学院/国际半导体学院, 重庆 400065
为了解决高分辨率逐次逼近模数转换器(SAR ADC)中,电容式数模转换器(DAC)的电容失配导致精度下降的问题,提出了一种电容失配自测量方法,以及一种可适用于各种差分电容DAC设计的低复杂度的前台数字校准方法。该方法利用自身电容阵列及比较器完成位电容失配测量,基于电容失配的转换曲线分析,对每一位输出的权重进行修正,得到实际DAC电容大小对应的正确权重,完成数字校准。数模混合电路仿真结果表明,引入电容失配的16位SAR ADC,经该方法校准后,有效位数由10.74 bit提高到15.38 bit。
逐次逼近模数转换器 数字校准 电容失配 SAR ADC digital calibration capacitor mismatch
重庆邮电大学 光电学院/国际半导体学院， 重庆 400065
采用0.35 μm CMOS工艺，设计了一种用于CdZnTe探测器的16通道高速前端读出电路。整体电路由16个模拟通道、偏置模块和逻辑控制模块组成，每个通道包括电荷敏感放大器、漏电流补偿电路、成形器、基线保持电路、峰值检测保持电路和时间甄别器。分析了高入射频率下主要电路模块的性能及通道的读出时序。仿真结果表明，本前端读出电路的输入能量范围为29~430 keV@1~15 fC，每个通道功耗小于1.8 mW，等效噪声电荷为87.6e-，最大能补偿的漏电流为50 nA，达峰时间为150 ns，通道增益为50 mV/fC，非线性小于1%，最高注入频率为500 kHz。
前端读出电路 CdZnTe探测器 高速 单光子发射计算机断层成像 front-end readout circuit CdZnTe detector high speed SPECT
1 天津大学 精密仪器与光电子工程学院 超快激光实验室，天津 300072
2 天津职业技术师范大学 电子工程学院，天津 300222
目前，飞秒激光脉冲因脉冲宽度窄和峰值功率高的特点被广泛运用在多种领域中。其中，色散管理光纤锁模激光器因其特有的腔内呼吸机制使输出的激光脉冲能量更高，光谱更宽、脉宽更窄。使用啁啾布拉格光纤光栅进行色散管理的光纤锁模激光器能够实现真正的全光纤结构，提升激光器的紧凑性和稳定性，因此基于啁啾布拉格光纤光栅进行色散管理的光纤锁模激光器具有更加实际的应用意义。采用数值模拟的方法，研究了基于啁啾布拉格光纤光栅进行色散管理的掺镱光纤锁模激光器中单模光纤在腔内的不同分布对脉冲动力学过程和输出脉冲参数的影响。系统分析了谐振腔内净色散值不同时，腔内单模光纤的分布对脉冲在腔内的动力学过程的影响。模拟结果表明，在腔内净色散值为负时，啁啾布拉格光纤光栅与增益光纤间的单模光纤越短，光纤激光器维持稳定单脉冲运行的最大泵浦强度更高且输出光谱更宽，从而能够获得脉宽更窄的去啁啾脉冲；腔内净色散值越接近零时，啁啾布拉格光纤光栅与增益光纤间的单模光纤长度对输出脉冲参数作用的影响越显著；腔内净色散值为正时，单模光纤在腔内的分布对输出脉冲影响逐渐减弱，优化单模光纤分布提升锁模激光器性能并不明显。最后，提出了一种通过改变单模光纤在腔内的分布来提高激光器输出性能的优化方法。
光纤激光器 锁模激光器 超快激光 啁啾布拉格光栅 fiber laser mode-locked laser ultrafast laser chirped fiber Bragg gratings 红外与激光工程
2022, 51(12): 20220226
Author Affiliations
Abstract
Ultrafast Laser Laboratory, Key Laboratory of Opto-electronic Information Science and Technology of Ministry of Education, School of Precision Instruments and Opto-electronics Engineering, , Tianjin 300072, China
Ultrafast lasers with high repetition rate, high energy, and ultrashort pulse duration have enabled numerous applications in science and technology. One efficient route to generate such pulses is postcompression of high-power Yb-doped lasers. Here, we report on the generation of 24.5 fs pulses with an output energy of 1.6 µJ and a repetition rate of 500 kHz. The pulses are obtained by using a hybrid cascaded nonlinear compression of the pulses delivered by a Yb-based fiber chirped pulse amplification (CPA) system. In the first stage, the initial 390 fs laser pulses are compressed to 100.7 fs based on spectral broadening in three fused silica plates. In the second stage, the pulses have been shortened to sub-30 fs by means of nonlinear compression in a hollow-core fiber. Overall, we could achieve times temporal shortening with the proposed approach. The results show that our system can effectively generate few-cycle pulses at a relatively high repetition rate and high energy, which can benefit future possible applications.
multiple-plate medium hollow-core photonic crystal fiber pulse compression Chinese Optics Letters
2022, 20(10): 100006
提出了一种偏振可调的太赫兹光电导天线, 其结构由四个弧形金属电极、低温砷化镓衬底和氮化硅抗反射涂层构成。通过对光电导天线的工作原理分析, 可以发现弧形金属电极结构决定天线的辐射偏振, 且衬底的载流子迁移率、载流子寿命和衬底材料对激光的吸收直接影响天线的辐射特性。利用COMSOL软件对该光电导天线进行建模仿真, 其结果表明该光电导天线可以在45°方向倍增地辐射线偏振太赫兹波, 且辐射强度相较于常规光电导天线提高了30%, 辐射带宽高达10THz。所设计太赫兹光电导天线具有偏振可调、结构简单和易于加工等特点, 在太赫兹光谱检测领域具有广阔的应用前景。
太赫兹 偏振可调 光电导天线 terahertz adjustable polarization photoconductive antenna
设计了一款可用于检测材料折射率及厚度的双开口环型太赫兹超材料传感器, 其结构由双开口方环与圆环嵌套的超材料结构和聚酰亚胺衬底两部分构成。当太赫兹波垂直入射超材料表面时, 该传感器结构在0.8~1.8THz范围内形成三个高Q值谐振峰（中心频率分别为f1, f2和f3）。通过探讨超材料结构表面电流分布与三个谐振峰形成的关系, 观察到超材料结构对入射太赫兹波的不同响应特性导致产生不同的表面电流分布。此外, 还对该传感器在折射率传感和厚度传感方面的应用进行了探究。在待测物厚度一定的情况下, 该传感器在谐振频率f1, f2和f3处的传感灵敏度分别可达170, 103和119GHz/RIU, 均具有优越的传感特性, 可利用其多谐振峰进行高灵敏度折射率传感。这种高灵敏度的多谐振峰折射率传感器可以检测到待测分析物的微小变化, 在生物化学检测领域具有广阔的应用前景。
太赫兹 超材料传感器 灵敏度 折射率 terahertz metamaterial sensors sensitivity refractive index
