38CrMoAl材料表面污染物激光清洗技术

采用脉冲激光对38CrMoAl材质样件进行了激光清洗试验研究,通过显微镜、白光干涉仪、台阶仪、红外测温仪等分析方法,研究了38CrMoAl材料表面污染物的清洗阈值、损伤阈值、激光功率密度对清洗效果的影响规律。结果表明,当激光功率密度大于1.22 J/cm2时,样件表面污染物开始被有效清除,对应污染物的清洗阈值,当能量密度增加到3.11 J/cm2时,38CrMoAl基材开始出现损伤,对应基材的损伤阈值;当能量密度位于清洗阈值和损伤阈值之间时,清洗机理主要为振动效应;当激光能量密度为2.36 J/cm2时,清洗效果最好,样件表面污染物去除干净,清洗前后表面粗糙度基本没有变化,基材无损伤,激光清洗可满足38CrMoAl材质样件的精密清洗需求。     

一维热应力模型在调Q短脉冲激光除漆中的应用

讨论了热应力在短脉冲激光清洗油漆过程中的作用,从一维热传导方程出发,计算了由热膨胀产生的热应力以及根据粘附力公式计算出了油漆的粘附力.通过比较热应力与粘附力大小,得到激光清洗油漆的条件,进而建立一维短脉冲激光除漆模型.根据此模型可计算出:波长为1064 nm,脉宽为10 ns的激光清除铁基底上厚度为40μm橙色漆的清洗阈值为0.5 J/cm2;不同能量密度下使得油漆脱落所需的激光作用时间;激光脉冲作用过程中铁基底的温度变化情况.实验所测得的清洗阈值为0.57 J/cm2,与理论结果接近.实验与理论都表明当能量密度过高时,铁基底的温度升高很大,超过其熔点,铁基底被损坏.并考虑了激光清洗铝基底上油漆的情况.     

Er:YAG激光和Er,Cr:YSGG激光消融牙釉质的阈值研究

通过离体牙实验,采用Er:YAG激光和Er,Cr:YSGG激光对人恒牙牙釉质进行消融阈值的实验研究.使用渐增的2～10 J/cm2能量密度对70个牙釉质样本进行辐照,应用体视显微镜和扫描电镜观察辐照后牙釉质表面的形态改变.结果表明,Er:YAG激光和Er,Cr:YSGG激光均能有效地消融牙釉质,Er:YAG激光消融牙釉质的阈值为3.19～4.36 J/cm2,Er,Cr:YSGG激光消融牙釉质的阚值为4.12～4.80 J/cm2.     

激光清洗应用于清除城市涂鸦

探索了激光清洗去除涂鸦这一新型应用,并且针对清洗技术中的关键问题——激光能量密度对清洗效率的影响,进行研究.给出TEA CO2激光在不同情况下的清除涂鸦的实验数据.验证了TEA CO2激光适用于激光清除涂鸦,效果显著.实验发现,当激光能量密度为4～6 J/cm2时,去除效率最高,实验中单位能量去除的涂鸦面积超过2.5 ...     

一种新型高峰值功率激光注入光纤耦合技术

分析了导光锥的导光原理和激光注入光纤耦合原理,通过射线理论分析并提出了导光锥的设计方法。通过对实验用导光锥进行导光率测试和耦合传输特性实验研究得到:导光锥的导光率为99%,导光锥与光纤耦合效率大于73%;导光锥端面的激光诱导损伤阈值能量密度为56 J/cm2,阈值功率密度为2.25 GW/cm2;在光纤发生端面损伤前其输出端输出激光能量达到50 mJ。采用导光锥实现高峰值功率脉冲激光注入光纤耦合可以有效地提高光纤传输激光容量。     

脉冲YAG激光清洗轮胎模具的实验研究

为了获得激光清洗轮胎模具的工艺参量,采用自主研制的平均功率达250W的脉冲式YAG激光清洗设备开展了轮胎模具激光清洗实验研究。取得了不同激光参量对轮胎模具清洗效果的实验数据,并研究了激光峰值功率、能量密度等参量与轮胎模具清洗速度、清洗效果的关系。结果表明,清洗轮胎模具脉冲YAG激光比CO₂激光更高效;轮胎模具清洗的激光能量密度阈值约为250mJ/mm2,提高激光峰值功率和平均功率能提高清洗速度和清洁效果。此结果为激光清洗设备的研究提供了参考。     

激光装置污染物诱导光学元件表面损伤实验研究

通过分析高功率激光装置内主要污染物成分及来源,研究其对大口径光学表面抗损伤能力的影响规律,得到装置光学表面洁净控制要求。利用扫描电镜对高功率激光装置内部的主要颗粒污染物进行取样分析;采用自然沉降的方法在光学元件表面制备污染物,并利用Nd∶YAG(SAGA-S)激光器研究其损伤阈值和损伤规律。研究结果表明,高功率激光装置内颗粒污染物的主要成分为金属、有机物和矿物质,占据比例分别为20%、40%和40%。激光辐照污染后的光学表面存在激光清洗和激光诱导损伤两种效应,当激光器能量密度超过10.9 J/cm2时,光学表面存在清洗作用。当激光能量密度超过14.6 J/cm2时,光学表面污染物引起损伤,且损伤随着污染物尺寸呈线性下降趋势。     

0.53 μm脉冲激光辐照可见光面阵CCD的实验研究

开展脉宽为10 ns、波长为0.53μm的脉冲激光辐照可见光面阵CCD的实验研究,测量了CCD从像元饱和、饱和串音到硬损伤的激光能量阈值。实验结果表明:像元饱和阈值为2.88~65.3μJ/cm2;饱和串音阈值为1.52×102~1.64×104μJ/cm2;CCD点损伤阈值为5.18×104μJ/cm2,点损伤原因是激光对CCD表面的热熔融作用。     

激光清洗铝合金漆层的数值模拟与表面形貌

采用COMSOL Multiphysics建立了纳秒脉冲激光清洗2024铝合金表面丙烯酸聚氨酯漆层的有限元模型,分析了不同参数对激光清洗温度场和清洗深度的影响,并进行了实验验证。结果表明:扫描速度以搭接率的形式影响清洗效率,扫描速度越慢,清洗速率越小,当搭接率为50%时具有合适的清洗效率;随着激光能量密度增加,漆层表面和基体表面的最高温度线性升高,当激光能量密度达到25 J/cm^2时,激光辐照区域的漆层材料完全被去除,铝合金基体的烧蚀深度为50μm;在激光能量密度为25 J/cm^2,搭接率为50%的实验参数下,基体表面沟槽峰谷高度为50.234μm,在此参数组合下可以获得良好的符合涂装工艺要求的表面。该结果可为研究纳秒脉冲激光清洗及其工艺参数的选择提供参考。     

激光清洗7075铝合金轮胎模具表面质量优化分析

使用脉冲光纤激光器对铝合金轮胎模具表面污染物的清除有助于提高轮胎生产的质量,延长轮胎的使用寿命。研究不同能量密度和扫描速度下激光清洗的效果,通过扫描电镜观察每次清洗后材料的表面形貌,使用SHR112便携式粗糙度仪测量每次清洗后试件的表面粗糙度,得到最优参数,通过能谱仪分析最优参数下实验前后材料表面元素变化情况。实验表明,在激光功率为25 W,激光重复频率为50 kHz,激光能量密度为25.5 J/cm²,扫描速度为120 cm/s时,可完全清除污渍,最终材料表面粗糙度约为3.17μm,符合行业标准。清洗过后试件表面O、S含量降低,Al含量升高。该实验的完成有效合理地对铝合金表面进行了清洗。     

Laser-induced desorption of atomic and molecular fragments from a tin dioxide surface modified by a thin organic covering of copper phthalocyanine

The systematic features of laser-induced desorption from an SnO₂ surface exposed to 10-ns pulsed neodymium laser radiation are studied at the photon energy 2.34 eV, in the range of pulse energy densities 1 to 50 mJ/cm². As the threshold pulse energy 28 mJ/cm² is achieved, molecular oxygen O₂ is detected in the desorption mass spectra from the SnO₂ surface; as the threshold pulse energy 42 mJ/cm² is reached, tin Sn, and SnO and (SnO)₂ particle desorption is observed. The laser desorption mass spectra from the SnO₂ surface coated with an organic copper phthalocyanine (CuPc) film 50 nm thick are measured. It is shown that laser irradiation causes the fragmentation of CuPc molecules and the desorption of molecular fragments in the laser pulse energy density range 6 to 10 mJ/cm². Along with the desorption of molecular fragments, a weak desorption signal of the substrate components O₂, Sn, SnO, and (SnO)₂ is observed in the same energy range. Desorption energy thresholds of substrate atomic components from the organic film surface are approximately five times lower than thresholds of their desorption from the atomically clean SnO₂ surface, which indicates the diffusion of atomic components of the SnO₂ substrate to the bulk of the deposited organic film.     

Non-destructive Raman evaluation of a heavily doped surface layer fabricated by laser doping with B-doped Si nanoparticles

The heavy B-doping of an intrinsic Si(1 0 0) wafer has been performed by irradiating a B-doped Si nanoparticle film on the surface of the Si(1 0 0) substrate with energy densities of 8.0 and 16.0 J/cm² by 532-nm laser light. The thicknesses of the heavily doped surface layers were investigated using Raman spectroscopy. The observed 488.0-nm-excited Raman bands were decomposed into two bands: a Fano-type band due to the heavily doped Si surface layer and a Voigt band due to the lightly doped, intrinsic Si region. The analysis of the Fano-type band indicated that the carrier concentration of the heavily doped region was larger than approximately 10¹⁹ cm⁻³. Based on the two-state model, the thicknesses of the heavily doped surface layers were 480 and 630 nm for the samples prepared with energy densities of 8.0 and 16.0 J/cm², respectively. These values were consistent with those obtained by secondary ion mass spectroscopy (SIMS).     

Optical emission characteristics of ablation plasma plumes during the laser-etching process of CdTe

Optical emission and surface compositional change during the laser-etching process of CdTe are reported. The etching rate increases in proportion to the laser energy density. However, the increase in etching rate is suppressed because ablation plasma plumes generated by the laser irradiation at the energy densities above 0.4 J/cm² shield the laser beam. The etching rate at the energy density of 1.0 J/cm² has been determined to be 91 nm/pulse. Also, 80-μm-deep and 55-μm-wide trenches have been formed with the laser-etching process.     

Numerical simulation of the dynamics of phase transitions in CdTe induced by irradiation with nanosecond pulses of an excimer laser

Simulation of the effect of KrF nanosecond pulse excimer laser radiation (λ = 248 nm, τ = 20 ns) on phase transitions in cadmium telluride was performed taking into account the diffusion of the melt components and their evaporation from the surface. It is shown that the surface region of the melt is enriched with tellurium due to the evaporation and diffusion of the cadmium telluride components. The obtained value 0.05 J/cm² of the threshold energy density for melting is in reasonable agreement with the experimental data.     

GaN基外延膜的激光剥离和InGaN LD外延膜的解理

利用波长为248nm的KrF准分子激光器进行了蓝宝石衬底GaN外延层剥离。对极薄的MOCVD生长的单层GaN外延膜(3μm)和InGaNLD外延膜(5μm)实现了大面积剥离。对剥离蓝宝石衬底背面抛光和未抛光外延片的不同特点作了比较,激光剥离所需的能量密度阈值分别约为200mJ/cm2和300mJ/cm2,优化结果表明,能量密度分别在400mJ/cm2和600mJ/cm2可实现稳定的剥离。同时对剥离后的InGaN多量子阱LD结构薄膜进行了解理,SEM观察显示获得的InGaNLD腔面平整光滑。基于这种技术可以获得无蓝宝石衬底的GaN基光电子和电子器件。     

染料调Q红宝石激光视网膜损伤阈值研究

本实验用染料调Q红宝石激光照射青紫蓝灰兔60只眼,求得视网膜凝固出血损伤阈值和单纯出血阈值分别为361μJ/cm2和481μJ/cm2,95%置信限分别为330μJ/cm2～394μJ/cm2和451μJ/cm2～514μJ/cm2。     

KrF准分子激光烧蚀氧化镁单晶的实验研究

本文采用光谱学和离子探针等检测手段,对KrF准分子激光烧蚀氧化镁单晶的物理过程进行了实验研究。结果表明,激光烧蚀等离子体内的主要粒子形态是镁原子和一价的镁离子,其粒子的动能在30～45eV范围。从烧蚀部位的扫描电镜形貌分析表明,在激光能量密度近于烧蚀阈值时,激光辐照的氧化镁单晶表面呈现出一定程度的层离特征。     

Laser annealing of ainc implanted GaAs

GaAs samples implanted with 1.10¹⁵ zinc ions/cm³ have been annealed using pulses from a ruby laser operating in the freely generated mode. The percentage electrical activities and peak carrier concentrations were found to depend on the implant temperature, the laser energy density and the number of pulses. The maximum hole concentration measured was about 1.10²⁰ cm^?3 following irradiation with four pulses of 3 J/cm². Significant residual damage remained after single pulse irradiation at this energy density value. However, the carrier mobilities were similar to values for good single crystal GaAs.     

Ion-Implantation-Induced Damage Characteristics Within AlN and Si for GaN-on-Si Epitaxy

A systematic study was conducted to further understand the physical origin of stress modification in AlN overgrown on Si(111) upon ion implantation and annealing. Implantation parameters including ion size, energy, dosage, and current density were varied, and their effects on the amorphization process in Si(111) substrates were examined. The creation of a thick (>120 nm) amorphous Si (a-Si) layer was previously shown to result in isolation of an epitaxial AlN film grown on a Si(111) substrate through implantation-induced amorphization of the substrate, and this mechanical isolation resulted in stress dilution in the AlN layer. Results show that implanting at current density of 2 mA/cm² allows for only a thin amorphous layer to be created because of the effects of dynamic annealing, which simultaneously eliminates any damage created from the ion implantation, regardless of ion species, dosage, and energy. Lowering the current density to 0.2 mA/cm² does create a thick a-Si layer; however, the amorphization disappears during a high-temperature (HT) anneal. Lowering the current further to 0.2 μA/cm² creates a thick a-Si layer that can be maintained through a HT anneal, with this difference arising from the interfacial quality of the a-Si and crystalline Si (c-Si) boundary.