共查询到20条相似文献,搜索用时 265 毫秒
1.
OFLID: Simple method of overlap factor calculation with laser intensity distribution for biaxial lidar 总被引:1,自引:0,他引:1
We proposed a simple overlap factor calculation method based on laser intensity distribution (OFLID), which is simple, practical and can be applied to any specific laser intensity distribution. In order to obtain the laser intensity distribution and parameters of our laser system, we designed a simple experiment to measure them, and then simulated an ideal Gaussian and uniform laser intensity distribution with the measured parameters. The OFLID calculation results indicated that the overlap factor of the measured distribution has approximately half the relative error of that of the ideal Gaussian distribution in the increasing range field for our lidar. Specifically, the laser intensity distribution should be regarded in the overlap correction of the lidar signal. Theoretically, the OFLID method can reduce the error caused by the hypothesis of ideal uniform or Gaussian intensity distributions in the analytical method. In addition, the method is easy to implement for overlap correction, signal simulation and system configuration optimization for biaxial lidar. 相似文献
2.
3.
五磷酸镧镱铒非晶在969nm激光激发下的1.54μm激光和上转换 … 总被引:4,自引:2,他引:2
本文了五磷酸镧镱铒YELPP非晶的吸收谱,计算了它的基本光谱参数,用半导体激光纵向泵浦方式,同1.54μm微片激光的连续运转,激光输出功率相当稳定,与九十年代初国际上的结果相当;还测量了1.54μm的激光有无振荡时的上转换发光,并且对两者的关系进行了初步的讨论。 相似文献
4.
激光能量注入可以控制Ⅳ型激波干扰,有效地减小钝头体压力载荷。基于有限体积法和分区结构网格划分的高分辨率数值方法,在来流马赫数为3.45的条件下,计算了单脉冲激光能量注入和连续激光能量注入对Ⅳ型激波干扰的影响。研究结果表明:单脉冲激光能量注入后一个较短时期内(50~60μs),钝头体表面压力突然升高,随后压力有一个较为明显的下降过程,然后恢复原状态;当注入的连续激光能量较小时,钝头体表面压力略微增大,随着注入能量增大,钝头体表面压力峰值减小;在注入能量到一定程度时,钝头体表面压力峰值减小已不明显。 相似文献
5.
We report an external cavity diode laser (ECDL), using a diode whose front facet is not anti-reflection (AR) coated that has
a mode-hop-free (MHF) tuning range greater than 135 GHz. We achieved this using a short external cavity and by simultaneously
tuning the internal and external modes of the laser. We find that the precise location of the pivot point of the grating in
our laser is less critical than commonly believed. The general applicability of the method, combined with the compact portable
mechanical and electronic design, makes it well suited for both research and industrial applications. 相似文献
6.
The results of a comparative study (theoretical and experimental) of two original approaches for spectral control of two-wavelength pulsed Ti:sapphire (Ti:S) lasers and the most popular conventional methods are presented. Single line operation as a particular case is considered. We compare our own methods: (i) combined dual pulse pumping–passive self-injection locking (DPP–PSIL) and (ii) coupled cavity dye laser injection locking (CCLIL) with the conventional methods: (i) intracavity selection (IS), (ii) PSIL and (iii) traditional injection locking using an external dye laser. The most important criteria—laser efficiency, emission line width, tuning range, spectral purity and buildup time are compared under optimized conditions. The comparison is made using the same pump source with constant output energy in each case. The results serve as a basis for choosing correctly the most suitable spectral control technique for a particular Ti:S laser application. It is shown that the DPP–PSIL method guarantees a remarkable improvement of the Ti:S laser performance (nearly doubling the laser efficiency with the same line width and comparable laser tuning range as IS, combined with a protection of the selectors). The CCLIL approach assures a maximum laser efficiency in narrow line emission in addition to a minimal and reproducible buildup time. The IS method provides a maximal tuning range. 相似文献
7.
Yan XQ Lin C Sheng ZM Guo ZY Liu BC Lu YR Fang JX Chen JE 《Physical review letters》2008,100(13):135003
A new ion acceleration method, namely, phase-stable acceleration, using circularly-polarized laser pulses is proposed. When the initial target density n(0) and thickness D satisfy a(L) approximately (n(0)/n(c))D/lambda(L) and D>l(s) with a(L), lambda(L), l(s), and n(c) the normalized laser amplitude, the laser wavelength in vacuum, the plasma skin depth, and the critical density of the incident laser pulse, respectively, a quasiequilibrium for the electrons is established by the light pressure and the space charge electrostatic field at the interacting front of the laser pulse. The ions within the skin depth of the laser pulse are synchronously accelerated and bunched by the electrostatic field, and thereby a high-intensity monoenergetic proton beam can be generated. The proton dynamics is investigated analytically and the results are verified by one- and two-dimensional particle-in-cell simulations. 相似文献
8.
This paper presents a novel effective method for optimizing laser cutting of specially shaped electronic printed circuit board (PCB) carrier substrates of advanced integrated circuit (IC) back-end packages that have multiple performance characteristics identified using grey relational analysis (GRA). Laser cutting parameters, including laser beam parameters (average laser power and Q-switch frequency), focusing parameters (laser beam focusing spot size), and machine parameters (laser cutting speed), were optimized based on multiple performance characteristics. Some characteristics of the specially shaped flash memory module for IC packages, such as smart disk (SD) cards are verified. The characteristics of interest are the average surface roughness on a PCB substrate cross-section, and the maximum width of the heat-affected zone (HAZ). Eight experiments were conducted using GRA to optimize the settings for laser beam cutting parameters to generate various quality characteristics. Analysis of the grey relational grade indicates that parameter significance and the optimal parameter combination for the laser cutting process are identified. The analytical results from two confirmation experiments using the optimal parameters confirm that laser cutting technology can be effectively applied to cut substrates into special shapes. 相似文献
9.
A method to generate a pulse sound source for acoustic tests based on nanosecond laser ablation with a plasma plume is discussed. Irradiating a solid surface with a laser beam expands a high-temperature plasma plume composed of free electrons, ionized atoms, etc. at a high velocity throughout ambient air. The shockwave generated by the plasma plume becomes the pulse sound source. A laser ablation sound source has two features. Because laser ablation is induced when the laser fluence reaches 1012–1014 W/m2, which is less than that for laser-induced breakdown (1015 W/m2), laser ablation can generate a lower sound pressure, and the sound source has a hemispherical radiation pattern on the surface where laser ablation is generated. Additionally, another feature is that laser-induced breakdown sound sources can fluctuate, whereas laser ablation sound sources do not because laser ablation is produced at a laser beam–irradiation point. We validate this laser ablation method for acoustic tests by comparing the measured and theoretical resonant frequencies of an impedance tube. 相似文献
10.
G. Zhang F. F. Luo X. F. Liu G. P. Dong Q. Zhang G. Lin Q. L. Zhou J. R. Qiu L. L. Hu D. P. Chen 《Laser Physics》2010,20(6):1425-1427
We experimentally demonstrated a single-mode laser at 1056 nm with Nd-doped phosphate glass microstructured optical fiber
(MOF), which was fabricated with conventional stack-and-draw method. The laser action was observed from a Fabry-Perot cavity
formed by placing two dichroic mirrors of ∼100 and 85% reflectivity, to the two end facets of MOF. Pumped by CW laser diodes
(LDs) at 808 nm, the MOF laser yielded a maximum output power of 8.5 mW and a slope efficiency of 2%. 相似文献
11.
Sho Itoh Hirofumi Hidai Hitoshi Tokura 《Applied Physics A: Materials Science & Processing》2013,112(4):1043-1049
The modification of transparent materials using a femtosecond laser has been studied. We previously proposed a new method of modifying glass using a continuous-wave laser, named continuous-wave laser backside irradiation (CW-LBI), in which CW laser illumination induces a change in the refractive index without cracking the glass. In this study, we investigated the process of glass modification by CW-LBI using time-lapsed imaging and by calculation of the temperature. First, the modification of glass was observed by the shadowgraph method, and it was found that thermal radiation was included in the phenomena that occurred when the glass was modified. Second, the time-lapsed temperature distribution was calculated. The temperature distribution was roughly in accordance with the shape of the modified area observed in the shadowgraphs. We concluded that the radius of the modified area is dependent on the temperature reached in the glass. 相似文献
12.
13.
A novel Fourier transform spectral interferometric (FTSI) multiplex coherent anti-Stokes Raman scattering (CARS) technique is developed to extract the vibrational spectrum equivalent to the spontaneous Raman scattering. The conventional FTSI method is modified to use the internal nonresonant CARS signal as a local oscillator to perform spectral interferometry. Utilizing the causality of the coherent vibration (i.e., there should be no signal before the laser excitation), this new FTSI method recovers the entire complex vibrational spectral parameters. We demonstrate this technique with a previously reported single-pulse multiplex CARS method that uses a single phase-controlled broadband ultrafast laser pulse. 相似文献
14.
E. Therssen Y. Bouvier C. Schoemaecker-Moreau X. Mercier P. Desgroux M. Ziskind C. Focsa 《Applied physics. B, Lasers and optics》2007,89(2-3):417-427
A new method is proposed to measure the ratio of the refractive index function of soot particles E(m) at the two fixed wavelengths:
532 and 1064 nm. Using a non-intrusive, in-situ laser based technique, the ratio E(m,1064 nm)/E(m,532 nm) can be determined
by comparing laser induced incandescence (LII) intensities at 532 and 1064 nm excitation wavelengths. The method consists
of selecting laser energies that insure the equality of the LII signals in the low fluence regime under given conditions.
Such equality is consistent with the fact that the soot particle will have reached the same temperature independently of the
laser wavelength, i.e. the soot particle has absorbed the same energy. As the absorbed energy is proportional to the laser
irradiance times E(m), the measurement of the laser energies required to insure perfect concordance of the LII intensities
(spatially and temporally) serves to deduce the ratio E(m,1064 nm)/E(m,532 nm). The method is demonstrated in an acetylene/air
flame, validated against extinction measurements performed by cavity ring-down spectroscopy (CRDS) by using laser radiations
at 532 nm and 1064 nm and finally applied to different flame conditions.
PACS 78.20.Ci; 78.90.+t; 81.05.Uw; 42.62.-b 相似文献
15.
16.
强激光加热旋转薄柱壳的参量选择分析 总被引:1,自引:0,他引:1
为了把激光加热静止圆柱壳的实验测量结果应用到旋转圆柱壳的激光参量估计中,研究了旋转圆柱壳的激光加热效率。用积分变换法得到了旋转圆柱壳的温度分布,分析了最大温升点相对激光峰值强度点的滞后现象。基于静止圆柱壳和薄壳假设,导出了旋转圆柱壳激光加热效率及估计辐照时间的表达式。对于旋转金属圆柱壳,最大温升点相对激光峰值强度点的滞后角和激光加热效率取决于无量纲参量DR(柱壳半径R与束斑半径r0之比)、DL(横向热扩散尺度4ατL与束斑半径r0之比)及DM(加热时间τL与柱壳旋转频率fR的乘积)。达到相同的最大温升时,旋转圆柱壳的激光辐照时间和静止圆柱壳的激光辐照时间之间存在与激光功率无关的非线性关系,而激光功率决定了所需的绝对激光辐照时间。 相似文献
17.
为防止激光诱导间质内热疗治疗肿瘤时激光光纤加热段周围组织的炭化,本文提出了一种采用深低温流体对激光光纤及其临近组织进行降温冷却的方法.为验证该方法的可行性,本文对采用该方法后激光间质内热疗过程中组织的传热问题进行了深入的数值研究.结果表明,深低温流体冷却方法可避免局部高温对组织的炭化,并显著扩展有效加热范围,从而对肿瘤实施高效的热凝固. 相似文献
18.
We report on a simple method with a high spectral and spatial resolution for mapping variations in the cavity resonance of a plano-planar broad-area laser based on frequency-selective feedback. The demonstration experiment uses a vertical-cavity surface-emitting-laser (VCSEL), in which growth induced inhomogeneities are of particular importance. It relies only on a standalone laser with a narrow-bandwidth passive filter avoiding the need for an expensive tunable laser or high-resolution spectrometer. 相似文献
19.
分析了kW级光纤激光器实现单模激光输出的模式控制方式。采用主振荡功率放大方式,实现了工作波长1.08 m、最大输出功率1.05 kW的全光纤单模激光输出。对激光光谱和光束质量随激光功率的变化等输出特性进行了研究,结果表明:随着激光功率的增大中心波长和光束质量无变化,但谱宽逐渐展宽。分析了激光光谱展宽的原因,认为随着激光功率的增大,光栅纤芯的折射率变化增大,引起本振级的谱宽展宽,而本振级因谱宽展宽引入的噪声在放大级被放大,再加上放大级本身引入的自发辐射,共同造成放大级的谱宽展宽。对光束质量变差的原因进行了分析,认为光纤弯曲导致原先在纤芯中传输的激光部分被泄露到包层中,从而使光束质量变差。 相似文献
20.
石墨烯拥有许多优异的性能,这些性能使石墨烯有望成为金属基复合材料的理想增强相。采用激光烧结的方法制备了石墨烯-铜纳米复合材料。X射线衍射(XRD)和Raman光谱测试结果表明,石墨烯存在于激光烧结所制备的纳米复合材料中。显微硬度测试结果显示,石墨烯的添加使得石墨烯-铜纳米复合材料的硬度比激光烧结纯铜的硬度提高了约22%。用电化学极化法研究了激光烧结的石墨烯-铜纳米复合材料和纯铜在3.5%(质量分数)NaCl溶液中的腐蚀行为,石墨烯-铜纳米复合材料的腐蚀电位比激光烧结纯铜的腐蚀电位略有降低,腐蚀电流也有所降低,说明其耐腐蚀性能较激光烧结纯铜略好。 相似文献