Optimum design of birefringent filter

Ｏｐｔｉｍｕｍｄｅｓｉｇｎｏｆｂｉｒｅｆｒｉｎｇｅｎｔｆｉｌｔｅｒ￥ＸＩＥＪｉａｎｐｉｎｇ；ＳｉｎＸｉａｏｑｕａｎ；ＷａｎｇＪｕｎｍｅｉ；ＬＩＵＹｕ；ＬＵＯＪｉｎｇ；ＷＵＹｕｎｘｉａ；ＭＩＮＧＨａｉ（ＤｅｐａｒｔｍｅｎｔｏｆＰｈｙｓｉｃｓ，Ｕｎｉｖｅ...     

An Efficient LD Pumped Nd:glass Laser

ＡｎＥｆｆｉｃｉｅｎｔＬＤＰｕｍｐｅｄＮｄ：ｇｌａｓｓＬａｓｅｒＬＵＪｉａｎｇ；ＷＡＮＧＹａｎｇｉｕｎ；ＨＵＡＮＧＺｈａｏｍｉｎｇ；ＪＩＮＺｈｅｎｈｏｎｇ（ＷａｖｅＳｃｉｅｎｃｅＬａｂ．，ＳｈａｎｇｈａｉＵｎｉｖｅｒｓｉｔｙ，Ｓｈａｎｇｈａｉ２０１８...     

Diode-Pumped Monolithic Nd:LMA Laser

Ｄｉｏｄｅ－ＰｕｍｐｅｄＭｏｎｏｌｉｔｈｉｃＮｄ：ＬＭＡＬａｓｅｒ￥ＬＵＪｉａｎｇ；ＨＵＡＮＧＺｈａｏｍｉｎｇ；ＪＩＮＺｈｅｎｈｏｎｇ；ＷＡＮＧＹａｎｇｊｕｎ（ＯｐｔｉｃａｌＦｉｂｅｒＩｎｓｔｉｔｕｔｅ，，ＳｈａｎｇｈａｉＵｎｉｖｅｒｓｉｔｙｏｆＳｃ...     

Texture Image Segmentation Using Talbot Effect

ＴｅｘｔｕｒｅＩｍａｇｅＳｅｇｍｅｎｔａｔｉｏｎＵｓｉｎｇＴａｌｂｏｔＥｆｆｅｃｔ￥ＷＡＮＧＷｅｎｌｕ；ＪＩＮＧｕｏｆａｎ；ＹＡＮＹｉｎｇｂａｉ；ＷＵＭｉｎｘｉａｎ（Ｄｅｐｔ．ｏｆＰｒｅｃｉｓｉｏｎＩｎｓｔｒｕｍｅｎｔｓ，ＴｓｉｎｇｈｕａＵｎｉｖｅｒ...     

Some Problems on Reconstruction of Soft X -ray Hologram with Visible Light

ＳｏｍｅＰｒｏｂｌｅｍｓｏｎＲｅｃｏｎｓｔｒｕｃｔｉｏｎｏｆＳｏｆｔＸ－ｒａｙＨｏｌｏｇｒａｍｗｉｔｈＶｉｓｉｂｌｅＬｉｇｈｔ￥ＣＨＥＮＪｉａｎｗｅｎ；ＸＵＺｈｉｚｈａｎ；ＺＨＵＰｅｉｐｉｎｇ；ＸＩＡＯＴｉｑｉａｏ；ＫＯＵＬｅｉｇａｎｇ；ＷＡＮＧＺｈ...     

Interaction of two two-level atoms with SU (1, 1 ) coherent states

Ｉｎｔｅｒａｃｔｉｏｎ ｏｆ ｔｗｏ ｔｗｏ－ｌｅｖｅｌ ａｔｏｍｓ ｗｉｔｈ ＳＵ（１，１）ｃｏｈｅｒｅｎｔ ｓｔａｔｅｓ￥ＳＯＮＧＴｏｎｇｑｉａｎｇ；ＦＥＮＧＪｉａｎ；ＷＡＮＧＷｅｎｚｈｅｎｇ；ＸＵＪｉｎｇｚｈｉ（ｌ）ＩｎｓｔｉｔｕｆｅｏｆＯｐｔ...     

Novel Scheme for Narrow Band Fiber Filter System

ＮｏｖｅｌＳｃｈｅｍｅｆｏｒＮａｒｒｏｗＢａｎｄＦｉｂｅｒＦｉｌｔｅｒＳｙｓｔｅｍＺＨＡＯＹｕｃｈｅｎｇ；ＪＩＡＮＳｈｕｉｓｈｅｎｇ；ＷＡＮＧＷｅｉ；ＴＩＡＮＷｅｎｑｉａｎｇ（ＮｏｒｔｈｅｒｎＪｉａｏｔｏｎｇＵｎｖｉｖｅｒｓｉｔｙ，Ｉｎｓｔｉｔｕｔｅ...     

Growth and Crystallization Habit of a Novel Substrate Crystal LiGaO_2

ＧｒｏｗｔｈａｎｄＣｒｙｓｔａｌｌｉｚａｔｉｏｎＨａｂｉｔｏｆａＮｏｖｅｌＳｕｂｓｔｒａｔｅＣｒｙｓｔａｌＬｉＧａＯ_２￥ＨＵＡＮＧＷｅｉｍｉｎｇ；ＸＵＪｕｎ；ＷＵＧｕａｎｇｚｈａｏ；ＤＥＮＧＰｅｉｚｈｅｎ；ＧＡＮＦｕｘｉ（ＳｈａｎｇｈａｉＩｎｓｔｉ?..     

Studying the Mode－Spectra Characteristics of An Above－Threshold Biased Semiconductor Laser

ＳｔｕｄｙｉｎｇｔｈｅＭｏｄｅ－ＳｐｅｃｔｒａＣｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆＡｎＡｂｏｖｅ－ＴｈｒｅｓｈｏｌｄＢｉａｓｅｄＳｅｍｉｃｏｎｄｕｃｔｏｒＬａｓｅｒ￥ＸＩＡＧｕａｎｇｑｉｏｎｇ；ＷＵＺｈｅｎｇｍａｏ；ＣＨＥＮＪｉａｎｇｕｏ；ＬＵＹｕｃｕ...     

Characteristics of Tellurite Neodymium-doped Glass Laser

ＣｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆＴｅｌｌｕｒｉｔｅＮｅｏｄｙｍｉｕｍ－ｄｏｐｅｄＧｌａｓｓＬａｓｅｒ￥ＸＵＢｉｎｇ；ＬＥＩＮｉｎｇ；ＷＵＪｉａｎｇｕａｎｇ；ＺＨＡＮＧＺｈｅｎｑｕａｎ；ＸＵＺｈｉｚｈａｎ（ＳｈａｎｇｈａｉＩｎｓｔｉｔｕｔｅｏｆＯｐｔ...     

纳秒激光在铜靶材中诱导冲击波的实验研究

基于聚偏二氟乙烯压电传感器, 对铜靶材中纳秒激光脉冲诱导的冲击波传播过程进行了实验研究, 给出了铜靶材内冲击压强随激光脉冲能量和靶材厚度的变化规律. 实验结果表明: 500 mJ激光脉冲能量作用到2 mm厚的铜靶材产生的冲击压强达到2.1 MPa; 激光脉冲能量从200 mJ 增加到500 mJ, 在铜靶材厚度为2和4 mm条件下, 冲击压强分别增加了162%和231%; 而当铜靶材厚度从2 mm增加到6 mm时, 在400和500 mJ激光脉冲能量作用下, 铜靶材内冲击压强分别降低了32%和49%.     

基于速度干涉仪的冲击波精密调速实验技术研究

冲击波精密调速技术是惯性约束聚变研究的关键技术之一. 针对冲击波精密调速诊断技术的要求, 以神光III原型上脉宽为3 ns的两台阶整形激光脉冲为源, 用石英晶体做窗口材料, 模拟了双冲击在石英晶体中传输和追赶的过程. 利用两发典型双冲击波调速的实验数据, 验证了神光III原型具有的精密调速能力. 实验结果表明, 在驱动源、 靶和诊断系统参数一致的条件下, 两发实验获得的实验结果中两次冲击出现的时刻, 冲击波速度都很一致. 通过精细分析, 发现在两次冲击交会的时刻, 干涉条纹清晰度和完整性变化最大, 最终数据处理获得的冲击波速度偏差也最大. 同时, 在二次冲击的冲击波速度有较大增加的条件下, 并没有观察到冲击波阵面的反射率的明显增加. 本文的实验结果作为一个数据依据, 为全面开展冲击波调速实验提供了有效的方法.     

强脉冲激光在AZ31B镁合金中诱导冲击波的实验研究

为了研究强脉冲激光在镁合金中诱导冲击波的衰减,采用Nd:Glass脉冲激光(1054 nm,23 ns)对AZ31B变形镁合金试样表面进行冲击,并利用响应快、测量范围大的PVDF压电膜传感器以及示波器实时测量了强脉冲激光在镁合金靶中诱导激光冲击波的相对压力.根据冲击波每次在靶材背面反射时,所经过距离的不同得到激光冲击波在镁合金中的衰减规律.结果表明,在激光能量为5J的强脉冲激光作用下,镁合金中冲击波衰减的平均速度为5.83×10³ m/s,与镁合金中应力波纵波的传播速度相符;强脉冲激光诱导冲击波在镁合金中是以指数规律衰减的.试验所得分析结果对激光冲击强化镁合金的应用具有重要意义. 关键词： 激光 镁合金 压电膜传感器 衰减规律     

激光引致激波演化数值研究

在高重复频率激光推进的研究中,激波的合并是发生在激波演化后期的,同时由于脉冲间隔短,脉冲宽度对流场演化的影响也需要详细研究。考虑了激光辐照过程对流场演化的影响,通过数值计算对激波演化特性进行了研究。结果表明,初期波阵面的椭球形状逐渐转化为一个球形,球心与击穿点的距离随时间逐渐减小并最终趋于稳定。基于激波合并的应用,当激波马赫数在1~2之间时,给出了激波波阵面半径随时间的变化规律,以及激波高压区长度和波峰压强随激波波阵面半径变化规律的经验公式。     

Impact of an extended source in laser ablation using pulsed digital holographic interferometry and modelling

Pulsed digital holographic interferometry has been used to study the effect of the laser spot diameter on the shock wave generated in the ablation process of an Nd:YAG laser pulse on a Zn target under atmospheric pressure. For different laser spot diameters and time delays, the propagation of the expanding vapour and of the shock wave were recorded by intensity maps calculated using the recorded digital holograms. From the latter, the phase maps, the refractive index and the density field can be derived. A model was developed that approaches the density distribution, in particular the ellipsoidal expansion characteristics. The induced shock wave has an ellipsoid shape that approaches a sphere for decreasing spot diameter. The ellipsoidal shock waves have almost the same centre offset towards the laser beam and the same aspect ratio for different time steps. The model facilitates the derivation of the particle velocity field. The method provides valuable quantitative results that are discussed, in particular in comparison with the simpler point source explosion theory.     

Ultra-fast diagnosis of shock waves and plasma at front and rear surfaces in the bulk of fused silica induced by an Nd:YAG pulse laser

We investigate the dynamic processes of the Nd:YAG pulse laser ablation of fused silica by ultrafast timeresolved optical diagnosis with a nanosecond time resolution. The evolution process of plasma expansion in air and shock waves propagation in the bulk are both obtained with spatial and temporal resolutions.Laser-induced damage in the bulk of fused silica with filaments and shock waves are observed. Thermoelastic wave,mechanical wave,and shock wave dependence on the laser fluence and intensity of the plasma are analyzed. The shock pressure P and temperature T calculated through the measured shock velocity D and the Hugoniot data of fused silica are measured.     

空气中激光支持爆轰波实验及理论分析

为了研究激光击穿空气产生的等离子体爆轰波形成机制和传播规律,利用高能量CO2激光器产生强激光,进行了空气中产生激光支持等离子体爆轰波实验。实验中:设置了诱导靶板,用于诱发和定位空气中的激光支持爆轰波;以激光器升压过程球隙放电产生的光信号作为触发源,触发高时间分辨率(纳秒级)的高速相机,记录了激光支持爆轰波的成长和传播全过程。分析了激光支持爆轰波的形成机理和传播规律。采用C-J爆轰理论,计算了激光支持爆轰波的压力和温度。研究结果表明:激光支持等离子体爆轰波形成初期,等离子体爆轰波发光体为球形;随着时间增加,等离子体爆轰波发光体的形状类似流星,且头部为等离子体前沿吸收层,亮度较高,而尾部等离子体温度较低,亮度较弱。等离子体爆轰波高速向激光源的方向移动,爆轰波速度高达18 km/s,温度约为107K。随着激光强度的减弱,爆轰波速度迅速按指数规律衰减,当爆轰波吸收的激光能量不能有效支持爆轰波传播时,爆轰波转变为冲击波。     

Shock-wave generation upon axicon focusing of femtosecond laser radiation in transparent dielectrics

It is shown experimentally that the axicon focusing of intense femtosecond laser pulses in transparent dielectrics leads to efficient excitation of shock waves. A method is developed for measuring the dynamics of shock waves, which uses a frequency-chirped probe pulse and has high spatial (～1 μm) and time (～10 ps) resolutions. The initial stage of the evolution of an intense (up to 10 GPa) shock wave is studied by this method.     

Generation of flexural waves in plates by laser-initiated airborne shock waves

Results of the semi-analytical modelling of the interaction of laser-initiated airborne shock waves with an infinite horizontally positioned elastic plate are presented. The impact of the airborne shock waves on the plate is approximated by a cylindrically diverging surface force resulting from the pressure of the incident and reflected shock waves. This force is then represented in the wavenumber-frequency domain by means of Hankel and Fourier transforms that are carried out numerically so that the interaction problem can be solved using the Green’s function method. The resulting frequency spectra and time histories of generated flexural wave pulses are calculated for different values of laser pulse energy and for different heights of the laser beam focusing above the plate surface. The theoretical results obtained are compared with the results of laboratory measurements of the interaction of laser-generated acoustic shocks with a large plastic plate. The comparison shows reasonably good agreement between the semi-analytical predictions and data.     

Effects of an absorptive coating on the dynamics of underwater laser-induced shock process

The effects of an absorptive coating on the dynamics of underwater laser-induced shock process have been observed from the end of laser pulse to hundreds of microseconds after irradiation by time-resolved imaging techniques. A laser pulse of 13 ns at 1,064 nm was focused by a 40-mm focal length lens onto the surface of epoxy-resin blocks immersed in water to induce the shock process in the confining regime. A custom-designed time-resolved photoelasticity imaging technique and a high-speed laser stroboscopic videography technique in photoelasticity mode were used to analyze the evolution of shock waves in the water phase, the strength of stress waves in the solid phase, the oscillation of cavitation bubbles, and the generation of bubble-collapse-induced shock waves. We showed that black paint coating enhances the strength of laser-induced stress wave inside the solid, drives faster shock waves traveling in the water phase, and produces higher-energy cavitation bubbles. We propose that even at power densities of 1 GW/cm² and above, an absorptive coating can intensify the shock process by enhancing the absorption of laser energy by plasma.