用斜入射方法计算碳纤维靶的激光增益

 用斜入射方法并考虑了激光被折射和P极化激光的共振吸收,计算了碳纤维靶的等离子体状态和激光增益。激光斜入射获得的类H碳的n=2 、3 跃迁的激光增益系数,比按垂直入射的计算的值略大,但是,增益系数的空间分布变得更窄。激光增益发生在更靠近靶的外表层。     

化学激光器1/4环柱型增益发生器

设计并搭建了化学激光器1/4环柱型增益发生器的实验系统。按设计流量进行了出光实验,功率计探测到的出光功率在60 W左右。测量了燃烧室温度及压力,与Alpha激光器HL911-3实验数据类似,燃烧室温度及压力曲线都存在一个爬升阶段。环柱型增益发生器沿角向扩张的特点使得光腔区压力很低,仅为0.5 kPa左右。为验证环柱状增益区的有效形成,对3对取光孔分别进行了出光实验,结果表明每对取光孔都有功率输出,证明设计的增益发生器运行正常。     

光纤回音壁模式的三波段激光辐射研究

将石英光纤浸入低折射率的激光染料溶液中构成圆柱形微腔.采用沿光纤轴向光抽运的消逝波激励增益方式,获得了沿光纤轴向长距离的激光染料增益,受激辐射光在圆柱形微腔中回音壁模式的支持下形成激光振荡.在直径为288 μm的同一根光纤外分三段分别填入罗丹明6G、罗丹明610和罗丹明640激光染料乙二醇溶液,实现了波长分别在567～575 nm、605～614 nm和656～666 nm三个不同波段的回音壁模式激光振荡,用一根光纤同时获得了红、橙、黄三种不同颜色的激光辐射.对实验所获得的回音壁模式激光光谱做了模式标定,依据标定的模式数计算了各种模式以及抽运光在光纤截面的强度分布.计算结果表明,激光增益区域总是局限在圆柱形微腔回音壁模式的模场区域内,由此可以显著地提高抽运效率,增加抽运光沿光纤轴向的增益长度.     

一种测量GaAs-GaAlAs行波激光放大器增益特性的实验方法

本文报导了一种测量光耦合效率η的新实验方法。这个方法是建立于p-n结短路光电流原理上的。本文推导出适合于行波激光放大器的光耦合效率的公式。短路光电流用一检流计测量,利用公式获得光耦合效率的实验值。利用实验所测光耦合效率,测量了行波激光放大器的增益随注入电流变化的规律,其结果和实验符合。另外本文还介绍了在脉冲注入电流条件下测行波半导体激光放大器增益的实验方法。     

复合泵浦双靶串接中等离子体的均匀性问题

在大功率激光装置上进行了预备性复合泵浦双靶串接实验中，利用针孔透射光栅谱仪对两路激光辐照靶产生的线状激光等离子体的均匀性进行了监测。分析和比较了单靶与串接靶线状等离子体均匀性的差异。     

Efficient multi-keV X-ray sources from Ti-doped aerogel targets

We have measured the production of hnu approximately 4.7 keV x rays from low-density Ti-doped aerogel (rho approximately 3 mg/cc) targets at the OMEGA laser facility (University of Rochester), with the goal of maximizing x-ray output. Forty OMEGA beams (lambda(L)=0.351 microm) illuminated the two cylindrical faces of the target with a total power that ranged from 7 to 14 TW. The laser fully ionizes the target (n(e)/n(crit)相似文献   

Mode-locked pulse generation from an all-FMF ring laser cavity

Experimental generation of stable mode-locked pulses and cylindrical vector beams(CVBs), from an all fewmode fiber(FMF) ring laser is first reported, to the best of our knowledge. In this laser, a section of few-mode erbium-doped fiber(FM-EDF) is used as the gain medium. The FM-EDF is pumped by 976 nm laser with LP11 mode, which is simultaneously converted and multiplexed through a homemade hybrid device, i.e., wavelength division multiplexing-mode selection coupler(WDM-MSC). All the components in our experiment are connected using FMF. The resulted CVB pulses have a spectral width of 0.33 nm with a repetition rate of 30.58 MHz under the pump power of 340 m W. Moreover, both azimuthally and radially polarized CVBs were achieved with a high purity of 95%. This mode-locked CVB fiber laser with an all FMF configuration opens the way to manipulate the transverse mode in mode-locked fiber lasers.     

Electron acceleration by laser produced wake field: Pulse shape effect

Analytical expressions are obtained for the longitudinal field (wake field: E_x), density perturbations () and the potential () behind a laser pulse propagating in a plasma with the pulse duration of the electron plasma period. A feasibility study on the wake field is carried out with Gaussian-like (GL) pulse, rectangular–triangular (RT) pulse and rectangular–Gaussian (RG) pulse considering one-dimensional weakly nonlinear theory (), and the maximum energy gain acquired by an electron is calculated for all these three types of the laser pulse shapes. A comparative study infers that the RT pulse yields the best results: In its case maximum electron energy gain is 33.5 MeV for a 30 fs pulse duration whereas in case of GL (RG) pulse of the same duration the gain is 28.6 (28.8)MeV at the laser frequency of 1.6 PHz and the intensity of 3.0 × 10¹⁸ W/m². The field of the wake and hence the energy gain get enhanced for the higher laser frequency, larger pulse duration and higher laser intensity for all types of the pulses.     

激光腔靶X射线面、体发射特性实验研究

介绍了在“神光”装置上进行的不同类型腔靶Ｘ射线面、体发射物理机制的实验研究。实验采用波长为１．０５３μｍ的激光,脉冲波形为高斯型,能量为５００一７００Ｊ／束,脉冲宽度为６００一１０００ｐｓ．典型靶由三个柱型腔组成,采取双束对打,两端的腔为吸收－转换区（源区）,中间腔为辐射加热的内爆区。给出源区及内爆区Ｘ射线面、体发射测量结果,并通过分析、估算给出面、体发射强度比。 关键词：     

柱形微腔回音壁激光光谱模式的精确标定

由柱形微腔中回音壁模式满足的本征值方程,得到确定回音壁模式位置和间距的近似解析公式。以此近似解析公式,首次对直径在215～328 μm间的5个柱形微腔回音壁激光光谱做了模式标定。在用近似解析公式对柱形微腔激光光谱的数值作拟合的计算中,除了回音壁模的径向模式数(l)和角动量模式数(n)外无需其他拟合参数,解析公式的拟合值和实验激光光谱波长值间的偏差小于0.05 nm,拟合结果精确可靠。柱形微腔回音壁激光光谱模式的精确标定在模式的场分布计算以及频移型微腔生物传感器的研究应用中具有重要作用,文章介绍的方法亦可应用于柱形微腔直径和折射率的精密测量。     

基于少模光纤被动调Q柱矢量光光纤激光器

通过单模光纤和少模光纤熔融拉锥耦合的方法制备出模式转换器,而后将一层多壁的碳纳米管薄膜作为可饱和吸收体覆盖到拉锥光纤的锥区,形成一种可饱和吸收体柱矢量光器件.结合调Q光纤激光器和模式转换器件的优势,可以简单高效地产生脉冲柱矢量光束,并得到具有峰值功率高、模式纯度高等特点的脉冲高阶模式激光输出.通过实验实现了中心波长为1560nm、最大单脉冲能量和最大峰值功率分别为116nJ和57mW的稳定调Q脉冲输出.通过调节光路中的偏振控制器,可以分别实现径向和角向偏振的调Q脉冲激光的输出.     

Modeling of large flattened mode area fiber lasers

Potentialities of independent tailoring the index and gain profiles in fiber laser aiming to achieve a strong modal discrimination are theoretically examined. It is demonstrated by numerical simulations existence of fiber amplifier constructions which have the flattened fundamental mode profile in the gain region. It is shown that the fundamental mode retain the largest modal gain in comparison with modal gains of higher-order-modes for any depletion of the gain by the fundamental mode. The particular design is presented with the flattened fundamental mode area 6360 μm squared.     

高功率梯度掺杂增益光纤温度特性理论研究

在高功率光纤激光器中, 增益光纤的热效应是限制激光功率进一步提高的重要因素之一. 为了降低增益光纤的最高温度, 提出了一种通过改变增益光纤的掺杂浓度分布, 分散光纤激光的热效应, 从而提高激光输出功率的方法. 基于速率方程模型和热传导模型, 在光纤激光放大器输出功率大致相当的情况下, 对几种不同掺杂方式下增益光纤中的热分布和放大器的输出功率进行了数值模拟. 研究结果表明: 增益光纤的梯度掺杂可以优化光纤中的温度分布并提高光纤熔接点的稳定性; 同时兼具提高输出光束的光束质量、抑制光纤中非线性效应和模式不稳定的效果, 是提高光纤激光放大器输出功率切实可行的办法. 研究结果可以为高功率光纤激光器中增益光纤的设计提供一定的参考.     

多芯光纤激光器增益场选模效应研究

对多芯光纤激光器的增益场选模效应进行了初步研究。利用矢量耦合模理论计算多芯光纤激光器支持的各类超模的模式特性,并对其增益系数进行计算,比较不同功率等级下各超模增益特性的异同。计算结果表明,在较低功率下。多芯光纤激光器各类超模增益系数大小基本一致,输出光束是由各超模组成的混合模式; 而当激光功率较高时,同相模的增益系数大小明显大于其它模式,在模式竞争中占据优势,激光器输出光束远场具备同相模的特征。最后对多芯光纤激光器增益场选模效应的适用范围进行了简单讨论。     

ICF流体力学不稳定性实验用柱状激波管的研制

在惯性约束聚变(ICF)实验中,点火靶丸表面(界面)的粗糙度和缺陷所产生的流体力学不稳定性是决定点火成功与否的关键因素之一,设计和研制流体力学不稳定性分解实验用靶是解决该问题的主要技术手段。结合国内外的研究现状和神光-Ⅱ激光装置的特点,设计并研制了一种新型柱状激波管。该靶型由三种介质组成,分别为调制聚苯乙烯(CH)圆片、柱状碳气凝胶(CRF)和CH微套管。调制CH圆片和柱状CRF通过微加工技术装配到CH微套管内,封装后形成柱状激波管。介绍了该靶型的设计原理和详细的制备工艺,并对相应的靶参数进行了测量。结果表明:柱状CRF气凝胶具有较好的成型性,长度、直径和密度分别为1000μm、730μm和250mg·cm-3;CH圆片的厚度和直径分别为15μm和730μm,表面调制图形的周期和峰谷差分别为100μm和4.3μm;实验得到的柱状激波管的轴向和径向最大装配误差分别为2μm和3μm。     

消逝波激励的双波段光纤回音壁模式激光辐射

将石英光纤浸入低折射率的染料溶液中后构成圆柱形微腔.采用轴向光抽运消逝波激励激光增益的方式,使增益区域局限在圆柱形微腔回音壁模式的模场区域内,由此显著地提高了抽运效率,增加了沿光纤轴向的增益长度.在一根石英光纤的轴向分段填入浓度同为2×10^-3mol/L的罗丹明6G和罗丹明B乙醇溶液,在567—576nm 和592—600nm的两个波长范围内同时获得回音壁模式的激光辐射;分段填入浓度为8×10^-4和8×10^-3mol/L的罗丹明B乙醇溶液, 关键词： 消逝波激励 圆柱形微腔 回音壁模式 双波段激光辐射     

980 nm泵浦激光二极管与柱形透镜光纤耦合的角向容忍度

给出了一个计算980 nm泵浦激光二极管与柱形透镜光纤耦合角向容忍度的理论模型,并选择圆形的柱透镜光纤进行数值计算,得出了在水平和垂直方向上偏转加平移时的相对耦合效率及绕光纤轴向转动的相对耦合效率的数值计算结果并加以分析,同时也研究了光纤透镜的形状和激光二极管与光纤的间距对相对耦合效率的影响.     

Multi-wavelength hybrid gain fiber ring laser based on Raman and erbium-doped fiber

A stable and uniform multi-wavelength fiber laser based on the hybrid gain of a dispersion compensating fiber as the Raman gain medium and an erbium-doped fiber (EDF) is introduced. The gain competition effects in the fiber Raman amplification (FRA) and EDF amplification are analyzed and compared experimentaUy. The FRA gain mechanism can suppress the gain competition effectively and make the present multi-wavelength laser stable at room temperature. The hybrid gain medium can also increase the lasing bandwidth compared with a pure EDF laser, and improve the power conversion efficiency compared with a pure fiber Raman laser.     

新型电光陶瓷调Q光纤激光器

报道了基于OptoCeramic(R)电光陶瓷材料的新型调Q光纤激光器.采用976 nm半导体激光器作为抽运源,电光陶瓷调制器作为Q开关,峰值吸收系数1200 Db/m的高掺杂镱纤作为增益介质构成环形腔激光器.增益光纤的高掺杂浓度使得激光器的腔长得到缩短,输出光脉冲的宽度得到压缩.通过调节电光元件的电压,控制材料的折射率,调节谐振腔的损耗,实现Q开关作用.实验中通过改变腔长、抽运功率和重复频率,研究了脉冲的输出特性.获得最窄脉宽104 ns,重复频率3～40 kHz连续可调的调Q脉冲输出.     

Laser ion-acceleration scaling laws seen in multiparametric particle-in-cell simulations

The ion acceleration driven by a laser pulse at intensity I= 10(20)-10(22) W/cm(2) x (microm/lambda)(2) from a double layer target is investigated with multiparametric particle-in-cell simulations. For targets with a wide range of thickness l and density n(e), at a given intensity, the highest ion energy gain occurs at certain electron areal density of the target sigma = n(e)l, which is proportional to the square root of intensity. In the case of thin targets and optimal laser pulse duration, the ion maximum energy scales as the square root of the laser pulse power. When the radiation pressure of the laser field becomes dominant, the ion maximum energy becomes proportional to the laser pulse energy.