Investigation of the mode splitting induced by electro-optic birefringence in a vertical-cavity surface-emitting laser by polarized electroluminescence

The mode splitting induced by electro-optic birefringence in a P-I-N InGaAs/GaAs/A1GaAs vertical-cavity surface- emitting laser （VCSEL） has been studied by polarized electroluminescence （EL） at room temperature. The polarized EL spectra with E｜｜[110] and E ｜｜ [150] directions, are extracted for different injected currents. The mode splitting of the two orthogonal polarized modes for a VCSEL device is determined, and its value increases linearly with the increasing injected current due to electro-optic birefringence; This article demonstrates that the polarized EL is a powerful tool to study the mode splitting and polarization anisotropy of a VCSEL device.

Adaptive split-step Fourier method for simulating ultrashort laser pulse propagation in photonic crystal fibres

In this paper, the generalized nonlinear Schrodinger equation （GNLSE） is solved by an adaptive split-step Fourier method （ASSFM）. It is found that ASSFM must be used to solve GNLSE to ensure precision when the soliton selffrequency shift is remarkable and the photonic crystal fibre （PCF） parameters vary with the frequency considerably. The precision of numerical simulation by using ASSFM is higher than that by using split-step Fourier method in the process of laser pulse propagation in PCFs due to the fact that the variation of fibre parameters with the peak frequency in the pulse spectrum can be taken into account fully.

Observation of Zeeman splitting effect in a laser-driven coil

The Zeeman splitting effect is observed in a strong magnetic field generated by a laser-driven coil.The expanding plasma from the coil wire surface is concentrated at the coil center and interacts with the simultaneously generated magnetic field.The Cu I spectral lines at wavelengths of 510.5541,515.3235,and 521.8202 nm are detected and analyzed.The splittings of spectral lines are used to estimate the magnetic field strength at the coil center as∼31.4±15.7 T at a laser intensity of∼5.6310^(15) W/cm^(2),which agrees well with measurements using a B-dot probe.Some other plasma parameters of the central plasma disk are also studied.The temperature is evaluated from the Cu I spectral line intensity ratio,while the electron density is estimated from the Stark broadening effect.

基于响应面法的Ni60/WC涂层表面织构皮秒分束工艺参数预测研究

目的实现六分束激光在Ni60/WC涂层表面烧蚀目标织构激光加工工艺参数的精确选择。方法基于CCD响应面法,设计在不同的激光工艺参数下对Ni60/WC涂层表面进行织构烧蚀试验,以激光频率、扫描次数、扫描速度为影响因素,以圆凹坑织构直径、深度及由其直径和深度综合加权所得的综合目标为响应目标,建立目标织构所需激光工艺参数的预测模型,以织构直径、深度及综合目标作为优化条件,对预测模型进行实验验证。结果扫描次数对织构直径的影响最显著,单个脉冲光斑上所聚集的能量大小是影响织构直径误差的关键因素。对织构深度影响最显著为扫描次数和频率,织构深度与扫描次数、频率呈正相关,不同因素间的交互作用是影响织构加工结果的关键。通过对预测模型所优选的参数进行实验验证发现,以织构直径和深度、综合目标建立的预测模型优选工艺参数所加工圆凹坑织构的质量评价指标与其预测指标的误差率分别为19.37%、3.57%。功率为6 W时,六分束激光加工最优工艺参数为速度5500 mm/s、频率400 kHz、扫描2次。结论通过综合目标建立的Ni60/WC涂层表面圆凹坑织构六分束激光加工参数优选预测模型精确程度较高,能够实现Ni60/WC涂层表面加工所需织构激光参数的准确预测,为涂层表面织构加工激光参数精确选择提供了理论依据。

透明硬脆材料激光剥离关键问题研究(特邀)

透明硬脆材料由于其优异的力学性能、热稳定性、耐腐蚀性以及光电性能,广泛应用于半导体与电子领域。传统透明硬脆材料切片方法效率低、材料损耗大,制约了硬脆材料的推广应用。激光剥离技术是近年来新兴的一种透明硬脆材料切片新方法,较传统金刚线切割方法大幅提升硬脆材料的切片效率和材料利用率,目前已发展成为硬脆材料激光加工领域学术研究与产业应用的焦点。文中深入分析透明硬脆材料激光剥离物理过程,归纳激光剥离过程关键科学问题:透明硬脆材料对激光的非线性吸收、激光作用下材料内部微观结构演化与缺陷扩展规律,以及激光光场调控对材料改质影响机制等。基于这些科学问题,综述了近年来激光剥离不同类型透明硬脆材料的研究进展,目前用于激光剥离的材料已涵盖了SiC、Si、GaN、金刚石等半导体材料,蓝宝石、多晶Al_(2)O_(3)、氧化锆等陶瓷材料,激光剥离技术已发展出超快激光双脉冲诱导剥离、超快激光-化学辅助剥离、多激光复合剥离等。激光剥离物理过程是一个典型的激光-材料-热学-力学多学科交叉问题,尽管在实验结果方面获得了显著突破和迅猛发展,但目前对于工艺机理仍缺乏深入的理论与数值建模研究。未来透明硬脆材料激光剥离技术将会朝着百微米以下超薄厚度剥离、改质层低损伤、工艺自适应等方向发展,将为半导体与电子等领域快速发展提供更大的技术支撑。

基于掺铒氟化物光纤的22.8μm可调谐激光输出

采用高浓度掺杂的掺铒氟化物光纤可以增强铒离子的能量转移上转换过程,从而产生2.8μm波段的中红外激光。铒离子的全波段发射光谱范围覆盖0.5~3.0μm,其发射波长与相应能级之间的跃迁相吻合。对铒离子全波段的激光输出开展了实验研究。由于氟化物掺铒光纤的高掺杂浓度, 2.8μm激光占据主导地位。当泵浦功率为2~4 W时,激光输出在2714~2784 nm范围内可调谐,这是由增益竞争和腔内选择性以及非均匀加宽效应造成的。当泵浦功率增加到3 W以上时,可以观察到激光的谱分裂现象。实验获得了2.8μm波段的高稳定中红外激光,最大输出功率为0.7 W,斜率效率为12%。

Sustainable Furfural Biomass Feedstocks Electrooxidation toward Value-Added Furoic Acid with Energy-Saving H_(2) Fuel Production Using Pt-Decorated Co_(3)O_(4) Nanospheres

Here,furfural oxidation was performed to replace the kinetically sluggish O_(2)evolution reaction(OER).Pt-Co_(3)O_(4)nanospheres were developed via pulsed laser ablation in liquid(PLAL)in a single step for the paired electrocatalysis of an H_(2)evolution reaction(HER)and furfural oxidation reaction(FOR).The FOR afforded a high furfural conversion(44.2%)with a major product of 2-furoic acid after a 2-h electrolysis at 1.55 V versus reversible hydrogen electrode in a 1.0-M KOH/50-mM furfural electrolyte.The Pt-Co_(3)O_(4)electrode exhibited a small overpotential of 290 mV at 10 mA cm^(-2).As an anode and cathode in an electrolyzer system,the Pt-Co_(3)O_(4)electrocatalyst required only a small applied cell voltage of~1.83 V to deliver 10 mA cm^(-2),compared with that of the pure water electrolyzer(OER||HER,~1.99 V).This study simultaneously realized the integrated production of energy-saving H_(2)fuel at the cathode and 2-furoic acid at the anode.

中红外量子级联激光器1×16锁相阵列设计

针对中红外波段单管量子级联激光器存在输出功率有限的问题,提出相干阵列通过光放大后合束提升激光器功率的方法,研究波长为4.6μm的1×16量子级联激光器锁相阵列的结构设计与优化。通过设计低传输损耗、高光限制因子的单模波导确定器件各层材料外延厚度;通过设计由100%反射率和50%反射率的布拉格反射镜组成的种子激光器实现4.6μm单波长激光输出;通过设计由1×2多模干涉耦合器(MMI)和弯曲波导组成的1×16分束器实现低损耗均匀分束并锁相;通过设计输出端口的Al_(2)O_(3)增透膜厚度并利用电注入放大的方式实现激光器阵列的大功率输出。最终确定波导上GaInAs层厚度为0.25μm,下GaInAs层厚度为0.1μm,上包层InP厚度为3μm,下包层InP厚度为1μm。当单模波导宽度为5μm时,波导损耗为0.055 dB·cm^(-1),光限制因子为0.733。100%反射镜刻蚀深度为0.2μm,周期为728 nm,占空比为0.5,周期数为1000;50%反射镜刻蚀深度为0.2μm,周期为727 nm,占空比为0.1,周期数为690;当阵列间距为35μm时,分束器尺寸为3080μm×605μm,损耗为0.254 dB,其中MMI尺寸为19μm×126μm;出射端口采用0.7μm的Al_(2)O_(3)增透膜,透射率达到0.975。最后比较了不同放大器阵列间距的温度与远场分布,相关研究结论可为量子级联激光器锁相阵列的研制提供设计参考。

连续频率量子射频电场测量技术研究

针对里德伯原子EIT-AT法射频电场测量方案中,测量频点带宽窄的问题,提供了一种宽带连续射频电场测量方法,并在TEM室中演示了量子射频电场探测系统的测量技术。该方法通过在TEM室内放置电场探头,基于非共振射频与里德伯原子的相互作用模型,在外加射频电场作用下,里德伯原子的能级产生偏移,根据光谱偏移变化量,反推出射频电场的强度大小。基于该方案实现了50~500 MHz范围内的连续频率不间断电场测量,极大的扩展了量子场强的应用范围,该方案同样可扩展至1 GHz以上的微波电场测量,该量子场强探头为光纤可解耦的结构,可以实现管道机箱等狭小空间的电场环境探测。

ANALYSIS OF NANO CHANNEL FORMATION IN QUARTZ CUBES BY LASER-INDUCED PROCESS

A novel laser processing technique was developed for making channels in the nano regime in this paper.A Nd:YAG laser was used to dry fabricate micro channels(25μm～100μm di- ameter)in a 1 cm^3 fused silica substrate by thermal-induced processing.By controlling the locations of these initiating micro channels on a silica cube,1D-controllable self-connecting nano fractures can be formed as rectangular channels.These nano channels are smooth and with extremely high aspect ratio(～10~4 depth to width ratio).A possible mechanism is proposed to explain the formation of the nano channels.This laser-based nano channel fabrication technique is fast and inexpensive,and with potential applications in capillary electrophoresis and electro-osmosis driven nano-filtration.

Laser direct writing derived robust carbon nitride films with efficient photon-to-electron conversion for multifunctional photoelectrical applications

Carbon nitride,an emerging polymeric semiconductor,has attracted attention in research ranging from photocatalysis to photodetection due to its favorable visible light response and high physicochemical stability.For its practical device application,the fabrication of high-quality carbon nitride films on substrates is essential.However,conventional methodologies to achieve high polymerization of carbon nitride are often accompanied by its decomposition,significantly compromising the film quality.Herein,we report an ultrafast fabrication of carbon nitride film by laser direct writing(LDW).The instantaneous high temperature and pressure during LDW can efficiently boost the polymerization of carbon nitride and suppress its decomposition,resulting in high-quality carbon nitride film with excellent mechanical stability with the substrate.Due to the efficient photon-to-electron conversion,it exhibits an outstanding photoelectrochemical water splitting and optoelectronic detection capability,even under strong acid/alkaline conditions.This study thus offers a facile and efficient LDW strategy for the rapid fabrication of carbon nitride film photoelectrodes,demonstrating its great feasibility in multifunctional photoelectrical applications,including but not limited to photoelectrochemical water splitting and optoelectronic detection.

The ablation characteristics of laser-assisted pulsed plasma thruster with metal propellant

In this study,a laser-assisted pulsed plasma thruster(LA-PPT)with a novel configuration is proposed as an electric propulsion thruster which separates laser ablation and electromagnetic acceleration.Owing to the unique structure of the thruster,metals can also be used as propellants,and a higher specific impulse is expected.The ablation quality,morphology,and plume distribution of various metals(aluminium alloy,red copper,and carbon steel)with different laser energies were studied experimentally.The ablation morphology and plume distribution of red copper were more uniform,as compared to those of other metals,and the ablation quality was higher,indicating its greater suitability for LA-PPT.The plume generated by nanosecond laser ablation of aluminium alloy expanded faster,which indicated that the response time of the thruster with aluminium alloy as the propellant was shorter.In addition,when the background pressure was 0.005 Pa,an obvious plume splitting phenomenon was observed in the ablation plume of the pulsed laser irradiating aluminium alloy,which may significantly reduce the utilisation rate of the propellant.

Spectral Correction Method of Multi-Channels Near-Infrared Spectrometer and Applications

Near-infrared (NIR) spectrometer based on semiconductor lasers can combine light source and splitter into one, which is an important direction for development of miniature instruments. In order to avoid random interference caused by inconsistency between light sources, the novel evaluation indicators for global stability of multi-channels spectral system were proposed based on the correlation between dynamic deviation spectra of any two channels. The NIR analysis of moisture for corn powder samples based on the partial least squares combined with Savitzky-Golay (SG) smoothing was taken as an example, and a spectral correction method for enhancing prediction performance of multi-channels spectral system was further provided using above evaluation indicators. The experiment results showed that the global stability evaluation indicators significantly increased after SG smoothing correction. Meanwhile, the root-mean-square errors of prediction for corn moisture reduced from 0.373 to 0.283 (%), and the correlation coefficient between predicted and actual values was improved from 0.702 to 0.855. The above results indicated that by improving global stability indicators, the prediction ability of multi-channels spectral system can be improved. The proposed method provided a valuable reference for designing multi-channels diminutive spectrometer with high prediction performance, which had significance for large-scale application of NIR technology.

利用激光气流分割技术同时测定斜长石的微量元素与Sr同位素

斜长石是火成岩中的主要造岩矿物之一。其微量元素和Sr同位素组成可以用来示踪多种地质过程。传统的斜长石研究需要进行2次独立的激光剥蚀电感耦合等离子体质谱分析,来分别测试微量元素和Sr同位素组成。然而对于具有复杂环带结构的斜长石, 2次激光剥蚀分析获得的微量元素和Sr同位素可能是解耦的。本研究采用近几年兴起的激光气流分割技术建立了通过1次激光剥蚀同时测试斜长石微量元素和Sr同位素的方法。该方法将1台激光剥蚀系统(LA)同时与1台高分辨率扇形磁场等离子体质谱(SF-ICP-MS)和1台多接收等离子体质谱(MC-ICP-MS)联机。在1次激光剥蚀过程中,通过Y形接头将激光剥蚀产生的气溶胶分为两路,一路气溶胶进入MC-ICP-MS进行同位素组成分析,另一路气溶胶进入SF-ICP-MS进行微量元素含量分析。使用本方法分析USGS玄武玻璃标样BHVO-2G和NKT-1G的Sr同位素组成和微量元素含量,分析结果在误差范围内均与推荐值或前人报道值一致。此外,本研究利用建立的方法对满洲里巴杨山塔木兰沟组火山岩中的斜长石斑晶进行了微量元素和Sr同位素的同时测试,并利用斜长石成分计算了平衡熔体的微量元素组成。分析认为,巴杨山玄武安山岩源区为俯冲板片流体交代过的岩石圈地幔,并在岩浆上升过程中发生了少量地壳混染作用。

基于保偏镜组的外差干涉测量几何误差分析

角锥棱镜由于本身缺陷会导致失偏效应。在平面镜外差干涉仪中,使用一种保偏反射镜组替代角锥棱镜,以减小外差干涉仪的非线性误差。根据这个平面镜外差干涉仪的基本光路图,基于偏振分光棱镜和角锥棱镜的基本光学特性,分析了平面镜外差干涉仪中3个偏振分光棱镜偏摆角、仰俯角和滚动角,保偏反射镜组中2个偏振分光棱镜之间的间距和角度,以及角锥棱镜的偏摆角和仰俯角等误差对干涉仪的影响。推导出外差干涉仪中各个光学元件的最大安装误差,并规定好其加工精度,确保外差干涉仪性能。

承力孔结构抗疲劳表面强化技术研究进展

孔结构是机械零件常见的细节结构,存在显著的应力集中,成为许多零件疲劳失效的裂纹起源。针对该结构开展包括直接芯棒冷挤压、开缝衬套冷挤压、激光冲击强化、喷丸强化及部分新技术研究的进展分析,从结构适应性、强化效果、尺寸保障等3个维度对比上述技术的特点,为针对性选用适宜表面强化工艺提供参考。结果表明:直接芯棒冷挤压工艺简单,其疲劳强化效果最佳,孔结构尺寸保障效果好,适用于两侧无干涉的孔结构强化;开缝衬套冷挤压强化采用C型衬套并需进行后加工以保障挤后孔径,工艺过程相对复杂,但其工艺特性适用于应力集中敏感材料制造的单侧干涉孔结构;激光冲击和喷丸强化影响层深度明显低于冷挤压强化,适用于光线可达或能够使茅枪伸入、实现弹丸反射的孔结构。

分叶法和整块法在经尿道低功率绿激光前列腺剜除术中的应用

目的:探讨在经尿道低功率绿激光前列腺剜除术(VREP)中不同剜除方法的临床疗效和安全性。方法:回顾性分析2020年8月—2021年8月在我院行VERP术的98例良性前列腺增生(BPH)患者的临床资料,随访1年。47例使用分叶法剜除,51例使用整块法剜除,将其分为分叶法组和整块法组,比较两组的剜除效率、粉碎效率、手术时间、术后血红蛋白(HGB)下降值、术后最大尿流率(Qmax)、国际前列腺症状评分(IPSS)、生活质量评分(QOL)、术后尿道狭窄及尿失禁的发生率。结果:两组剜除效率[(1.25±0.7)g/min vs.(1.24±0.8)g/min]、粉碎效率[(4.37±2.9)g/min vs.(4.32±2.7)g/min]、术后HGB下降值[(8.5±4.3)g/L vs.(8.2±4.4)g/L]的差异无统计学意义(均P>0.05)。两组术后3个月随访的Qmax[(21.6±3.5)mL/s vs.(21.3±3.6)mL/s]、IPSS[(8.8±1.8)分vs.(8.5±1.9)分]和QOL[(1.7±0.4)分vs.(1.8±0.3)分]的差异也无统计学意义(均P>0.05)。两组术后尿道狭窄的发生率相当(P>0.05)。分叶法组与整块法组的手术时间[(68.8±24.8)min vs.(82.5±30.9)min]和术后短暂性尿失禁发生率(4.3%vs.11.8%)的差异均有统计学意义(均P<0.05)。结论:在VREP中,分叶法和整块法疗效相当,但分叶法有更短的手术时间和更低的短暂性尿失禁发生率。

可提升被动锁模光纤激光器计算效率的分步傅里叶全局误差局部能量法

本文提出了一种提高被动锁模光纤激光器计算效率的方法,该方法由对称分步傅立叶方法(SSFM)和全局误差局部能量(GELE)方法组成。该方法可将与全局误差相关的局部能量增量限制在一定范围内来控制步长。该方法具有自动步长调整机制。达到同程度的计算精度,本文方法的计算时间为255 s,而小的恒定步长SSFM方法需要3 855 s。这表明本文方法可以将计算效率提高10余倍。本文方法还可以通过RK4IP、Adams、预测-校正等高阶算法进行扩展,以提高精度。

多色分图层激光扫描自聚焦投影技术

为了突破常规激光投影仪由于单一波长的局限性造成应用场景的限制,同时实现对不同零件、不同材料、不同装配工艺的分图层投影,设计并搭建了多色分图层激光扫描自聚焦投影系统。系统采用2种波长的激光作为光源,根据二向色镜的位置不同,提出了多色共光轴和分光路2种激光扫描自聚焦投影方案,并推导了相应的光学系统数学模型。通过系统的自聚焦功能调节镜组间距,均可以实现在不同距离的投影面上聚焦出不同颜色的最小光斑。利用ZEMAX光学设计软件对2种投影光学系统进行仿真,并从系统可靠性和投影效果上对2种系统进行比较分析。实验结果表明:在3 m处的投影面上,共光轴系统各种波长的光斑直径均在0.8 mm以内,且光斑大小均匀,可以实现多色分图层的扫描自聚焦投影功能。

Saturated absorption spectrum of cesium micrometric-thin cell with suppressed crossover spectral lines

Micrometric-thin cells(MCs)with alkali vapor atoms have been valuable for research and applications of hyperfine Zeeman splitting and atomic magnetometers under strong magnetic fields.We theoretically and experimentally study the saturated absorption spectra using a 100-μm cesium MC,where the pump and probe beams are linearly polarized with mutually perpendicular polarizations,and the magnetic field is along the pump beam.Because of the distinctive thin chamber of the MC,crossover spectral lines in saturated absorption spectra are largely suppressed leading to clear splittings of hyperfine Zeeman transitions in experiments,and the effect of spatial magnetic field gradient is expected to be reduced.A calculation method is proposed to achieve good agreements between theoretical calculations and experimental results.This method successfully explains the suppression of crossover lines in MCs,as well as the effects of magnetic field direction,propagation and polarization directions of the pump/probe beam on saturated absorption spectrum.The saturated absorption spectrum with suppressed crossover lines is used for laser frequency stabilization,which may provide the potential value of MCs for high spatial resolution strong-field magnetometry with high sensitivity.