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Sensitivity Improvements for Picosecond Ultrasonic Thickness Measurements in Gold and Tungsten Nanoscale Films

Nanomanufacturing and Metrology 2024年第2期7卷 1-12页

作者： Jiaqi Dong Chengyuan Yao Yuanhao Zhu Shaojie Li Bowen Liu JinTao Fan Chunguang Hu youjian song Minglie Hu Key Laboratory of Opto-Electronic Information Science and Technology of Ministry of Education School of Precision Instruments and Opto-Electronics EngineeringTianjin UniversityTianjin 300072China State Key Laboratory of Precision Measuring Technology and Instruments Tianjin UniversityTianjin 300072China

Picosecond ultrasonics,as a nondestructive and noncontact method,can be employed for nanoscale metallic film thickness *** sensitivity of the system,which determines the measurement precision and practicability of this technique,is often limited by the weak intensity of the ultrasonic *** solve this problem,we investigate the distinct mechanisms involved in picosecond ultrasonic thickness measurement for two types of metals,namely tungsten(W)and gold(Au).For thickness measurement in W films,theory and simulation show that optimizing the pump and probe laser wavelengths,which determine the intensity and shape of the ultrasonic signal,is critical to improving measurement sensitivity,while for Au film measurements,where acoustic-induced beam distortion is dominant,the signal intensity can be optimized by selecting an appropriate aperture size and sample *** above approaches are validated in experiments.A dual-wavelength pump-probe system is constructed based on a passively mode-locked ytterbium-doped fiber *** smoothing method and multipeak Gaussian fitting are employed for the extraction of ultrasonic *** measurement precision is achieved in a series of W and Au films with thicknesses of 43-750 *** work can be applied to various high-precision,noncontact measurements of metal film thickness in the semiconductor industry.

关键词： Picosecond ultrasonics Thickness measurement Optical pump-probe Beam distortion technique

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高聚物胶凝戈壁土的动残余变形特性试验研究

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地震工程与工程振动 2024年第4期44卷 222-233页

作者：宋优建杨海华杨武高鹏展沈静东新疆农业大学水利与土木工程学院新疆乌鲁木齐830052 新疆水利工程安全与水灾害防治重点实验室新疆乌鲁木齐830052

高聚物胶凝戈壁土是将高聚物与戈壁土按一定比例拌合而成的,可有效提高戈壁土的力学性能。为研究高聚物胶凝戈壁土的动残余变形特性,采用中型动三轴试验研究了高聚物质量比、围压、固结比和动应力比等对高聚物胶凝戈壁土残余剪应变和残... 详细信息

高聚物胶凝戈壁土是将高聚物与戈壁土按一定比例拌合而成的,可有效提高戈壁土的力学性能。为研究高聚物胶凝戈壁土的动残余变形特性,采用中型动三轴试验研究了高聚物质量比、围压、固结比和动应力比等对高聚物胶凝戈壁土残余剪应变和残余体应变的影响。结果表明:高聚物胶凝材料能有效降低戈壁土的动残余变形,高聚物胶凝戈壁土在经受30次循环荷载后产生的残余剪应变为天然戈壁土的15.0%~18.8%,残余体应变为天然戈壁土的12.1%~22.2%;掺入高聚物质量比为3%和12%时,残余剪应变的减小幅度为85.0%、95.2%,残余体应变的减小幅度为87.9%、95.5%,且高聚物质量比越大,减小幅度越大。采用投影寻踪回归(projection pursuit regression,PPR)分析了各影响因数对残余变形的影响权重,得出高聚物胶凝戈壁土动残余剪应变和残余体应变的影响权重依次为高聚物质量比、围压、动应力比和固结比。采用指数函数对高聚物胶凝戈壁土的残余变形与振次的关系进行拟合,建立了能反映高聚物质量比影响的高聚物胶凝戈壁土的修正残余变形模型。

关键词：高聚物胶凝戈壁土动三轴试验残余剪应变残余体应变投影寻踪回归分析残余变形模型

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High pulse energy femtosecond large-mode-area photonic crystal fiber laser

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Chinese Science Bulletin 2008年第23期53卷 3741-3745页

作者： song youjian HU MingLiet ZHANG Chi CHAI Lu WANG ChingYue Ultrafast Laser Laboratory College of Precision Instruments and Opto-electronics Engineering Key Laboratory of Opto-electronicInformation Science and Technology of Ministry of Education Tianjin University Tianjin 300072 China

A high pulse energy femtosecond fiber laser based on a large-mode-area photonic crystal fiber is demonstrated. A segment of Yb-doped single-polarization large-mode-area photonic crystal fiber with extremely low nonlinearity is explored as gain media of this fiber laser, resulting in intrinsically environmentally stability. The fiber laser is based on a linear cavity with dispersion compensation free configuration, and the stable mode-locking is obtained by a semiconductor saturable absorber mirror (SESAM). The fiber laser directly generates 2.5 W of average power at a repetition rate of 51.4 MHz, corresponding to a single pulse energy of 50 nJ. The output pulse duration is 4.2 ps, which is dechirped to 410 fs after extracavity dispersion compensation. The nonlinear absorption of SESAM determines the pulse shaping at low output power, while the mode-locking mechanism is under the balance between spectrum broadening from self-phase-modulation and gain filtering at the high output power.

关键词：光晶体纤维光纤激光器脉冲能耗大模式纤维

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High pulse energy fiber/solid-slab hybrid picosecond pulse system for material processing on polycrystalline diamonds

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High Power Laser Science and Engineering 2018年第2期6卷 38-44页

作者： Wei Chen Bowen Liu youjian song Lu Chai Qianjin Cui Qingjing Liu Chingyue Wang Minglie Hu Ultrafast Laser Laboratory Key Laboratory of Opto-Electronic Information Technology Ministry of Education School of Precision Instrument and Opto-Electronics Engineering Tianjin University Laize Photonics Co. Ltd

We demonstrate an all polarization-maintaining(PM) fiber mode-locked laser seeded, hybrid fiber/solid-slab picosecond pulse laser system which outputs 40 μJ, 10 ps pulses at the central wavelength of 1064 nm. The beam quality factors M2 in the unstable and stable directions are 1.35 and 1.31, respectively. 15 μJ picosecond pulses at the central wavelength of 355 nm are generated through third harmonic generation(THG) by using two Li B3 O5(LBO) crystals, in order to get better processing efficiency on polycrystalline diamonds. The high pulse energy and beam quality of these ultraviolet(UV) picosecond pulses are confirmed by latter experiments of material processing on polycrystalline diamonds. This scheme which combines the advantages of the all PM fiber mode-locked laser and the solid-slab amplifier enables compact, robust and chirped pulse amplification-free amplification with high power picosecond pulses.

关键词： all polarization-maintaining fiber chirped pulse amplification free amplification hybrid fiber/solid slab material processing mode-locked laser

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Nonlinearity optimization of dissipative-soliton fiber laser for generation of pulses with 350 kW peak power

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High Power Laser Science and Engineering 2018年第2期6卷 98-102页

作者： Han Chi Bowen Liu youjian song Minglie Hu Lu Chai Weidong Shen Xu Liu Chingyue Wang Ultrafast Laser Laboratory Key Laboratory of Opto-electronic Information Technology (Ministry of Education) School of Precision Instruments and Optoelectronics Engineering Tianjin University Department of Electrical and Computer Engineering Colorado State University State Key Laboratory of Modern Optical Instrumentation Zhejiang University

We demonstrate a nonlinearity optimization method by altering distribution of passive fibers in a dissipative-soliton mode-locked fiber laser to level up output parameters. In the numerical simulation, we found that the passive fiber segment after gain fiber characterizes the highest average B-integral among fiber segments. By reducing the length of this fiber section and keeping the total passive fiber length as constant, the output pulse energy can be effectively scaled up while maintaining a short dechirped pulse duration, resulting in boosting peak power. With this method, 37-n J pulses are generated from a dissipative-soliton mode-locked cladding pumped ytterbium-doped single-mode fiber laser in the experiment. The pulse can be dechirped to 66 fs with 350 k W peak power. Moreover, the pulse pedestal is suppressed by a vector-dispersion compressor.

关键词： fiber optics amplifiers and oscillators ultrafast lasers

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Review of low timing jitter mode-locked fiber lasers and applications in dual-comb absolute distance measurement

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Nanotechnology and Precision Engineering 2018年第4期1卷 205-217页

作者： Haosen Shi youjian song Runmin Li Yuepeng Li Hui Cao Haochen Tian Bowen Liu Lu Chai Minglie Hu Ultrafast Laser Laboratory Key Laboratory of Opto-electronic Information Technology Ministry of Education School of Precision Instruments and Opto-electronics Engineering Tianjin University

Passively mode-locked fiber lasers emit femtosecond pulse trains with excellent short-term stability. The quantum-limited timing jitter of a free running femtosecond erbium-doped fiber laser working at room temperature is considerably below one femtosecond at high Fourier frequency. The ultrashort pulse train with ultralow timing jitter enables absolute time-of-flight measurements based on a dual-comb implementation, which is typically composed of a pair of optical frequency combs generated by femtosecond lasers. Dead-zone-free absolute distance measurement with sub-micrometer precision and kHz update rate has been routinely achieved with a dual-comb configuration, which is promising for a number of precision manufacturing applications, from large step-structure measurements prevalent in microelectronic profilometry to three coordinate measurements in large-scale aerospace manufacturing and shipbuilding. In this paper, we first review the sub-femtosecond precision timing jitter characterization methods and approaches for ultralow timing jitter mode-locked fiber laser design. Then, we provide an overview of the state-of-the-art dual-comb absolute ranging technology in terms of working principles, experimental implementations, and measurement precisions. Finally, we discuss the impact of quantum-limited timing jitter on the dual-comb ranging precision at a high update rate. The route to highprecision dual-comb range finder design based on ultralow jitter femtosecond fiber lasers is proposed.

关键词： Timing jitter Mode-locked lasers Dual-comb Absolute distance measurement

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xtraction of internal phase motions in femtosecond soliton molecules using an orbital-angular-momentum-resolved method

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Photonics Research 2020年第10期8卷 1580-1585页

作者： YUWEI ZHAO JNTAO FAN youjian song UWE MORGNER MINGLIE HU Uitrafast Laser Laboratory Key Laboratory of Opto-electronic Information Science and Technology of Mlinistry of EducationSchool of Precision Instruments and Opto-electronics EngineeringTianjin UniversityTianjin 300072China Institut fiur Quanteroptik Leibniz Universitat HannoverWelfengarten 130167 HaninaverGermeny Cluster of Excellence PhoenixD(Photonics Opticsand Engineering-rnrnovation Across Disciplines)30167 HannoverGermany Laser Zentrum Hannover e.V Hollerithalice 830419 HannoverGermany

Internal motions in femtosecond soliton molecules provide insight into universal collective dynamics in various nonlinear *** we introduce an orbital-angular-momentum(OAM)-resolved method that maps the relative phase motion within a femtosecond soliton molecule into the rotational movement of the interferometric beam profile of two optical *** this means,long-term relative phase evolutions of doublet and triplet soliton molecules generated in an all-polarization-maintaining mode-locked Er-fiber laser are *** simple and practical OAM-resolved method represents a promising way to directly visualize the complex phase dynamics in a diversity of multisoliton structures.

关键词： polarization soliton resolved

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Sub-30 fs Yb-fiber laser source based on a hybrid cascaded nonlinear compression approach

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Chinese Optics Letters 2022年第10期20卷 25-29页

作者： Youming Liu Bowen Liu youjian song Minglie Hu Ultrafast Laser Laboratory Key Laboratory of Opto-electronic Information Science and Technology of Ministry of EducationSchool of Precision Instruments and Opto-electronics EngineeringTianjin UniversityTianjin 300072China

Ultrafast lasers with high repetition rate,high energy,and ultrashort pulse duration have enabled numerous applications in science and *** efficient route to generate such pulses is postcompression of high-power Yb-doped ***,we report on the generation of 24.5 fs pulses with an output energy of 1.6μJ and a repetition rate of 500 *** pulses are obtained by using a hybrid cascaded nonlinear compression of the pulses delivered by a Yb-based fiber chirped pulse amplification(CPA)*** the first stage,the initial 390 fs laser pulses are compressed to 100.7 fs based on spectral broadening in three fused silica *** the second stage,the pulses have been shortened to sub-30 fs by means of nonlinear compression in a hollow-core ***,we could achieve∼16 times temporal shortening with the proposed *** 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.

关键词： multiple-plate medium hollow-core photonic crystal fiber pulse compression

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Spectral filtering effect on multi-pulsing induced by chirped fiber Bragg grating in dispersion-managed mode-locked Yb-doped fiber lasers

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High Power Laser Science and Engineering 2021年第3期9卷 94-100页

作者： Dongyu Yan Bowen Liu Defeng Zou Jie Guo Yuxi Chu youjian song Minglie Hu Ultrafast Laser Laboratory School of Precision Instrument and Optoelectronics EngineeringKey Laboratory of Optoelectronic Information Technology(Ministry of Education)Tianjin UniversityTianjin 300072China

We numerically and experimentally investigate the multi-pulsing mechanism in a dispersion-managed mode-locked Ybdoped fiber ***-pulsing occurs primarily owing to the inherent filtering effect of the chirped fiber Bragg *** spectral filtering effect restricts the spectral broadening induced by self-phase modulation and causes extra loss,leading to a decreased pump power threshold for the multi-pulsing *** simulations show that multi-pulsing emerges at a lower pump power when the spectral filter bandwidth becomes *** the experiment,the spectral width increases as the net cavity dispersion approaches *** with wider spectral widths experience more loss from the spectral filtering effect,leading to a decreased pump power threshold for ***,the net cavity dispersion also has an impact on the multi-pulsing *** on this conclusion,we devise a strategy to obtain single-pulsing operation with the shortest pulse width and the highest pulse energy.

关键词： fiber optics oscillators nonlinear fiber optics ultrafast lasers

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Passive optimization of pump noise transfer function by narrow band-pass filtering in femtosecond fiber lasers

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High Power Laser Science and Engineering 2019年第3期7卷 156-162页

作者： Peng Qin Sijia Wang Minglie Hu youjian song Qian Xuesen Laboratory of Space Technology China Academy of Space TechnologyBeijing 100094China Ultrafast Laser Laboratory Key Laboratory of Opto-electronic Information Technical Science of Ministry of EducationSchool of Precision Instruments and Opto-electronics EngineeringTianjin UniversityTianjin 300072China

Fluctuation of pump power is one of the major sources of temporal and intensity noise in femtosecond fiber *** this work,the transfer functions between the relative intensity noise(RIN)of the pump laser diode(LD)and the output RIN,between the RIN of the pump LD and timing jitter of femtosecond fiber lasers are systematically *** is demonstrated,for the first time to our knowledge,that the amplitude of the pump RIN transfer function can be effectively decreased by an intra-cavity narrow band-pass *** particular,for normal-dispersion lasers,the 3-d B bandwidth of the transfer function can also be narrowed by two-thirds,with a steeper falling ***,with the narrow band-pass filtering,the transfer function is almost independent of the net intra-cavity dispersion due to amplifier similariton *** proposed scheme can effectively isolate the pump-induced noise without the need of complex active pump LD control and intra-cavity dispersion management,thus providing an easy way for practical high-power,high-stability femtosecond fiber laser design and related high-precision applications outside the laboratory.

关键词： band-pass filter femtosecond fiber lasers transfer function

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