高能飞秒激光系统中空间滤波器的研究和设计

 由于透镜传输时间延迟效应（PTD），飞秒激光脉冲经过空间滤波器产生脉冲波前变形。讨论了用双胶合透镜或双分离透镜代替空间滤波器中的单透镜，以消除或减小PTD效应，设计了适用于飞秒激光装置的空间滤波器。     

基于晶体旋光效应的近场光学空间滤波

 在激光传输与放大系统中，激光束的空间滤波是光束质量控制的重要环节。利用各向同性晶体的旋光性，采用偏振光检偏法选择不同空间频率光束的通过与阻挡，实现激光光束的近场空间滤波。用多个滤波器串接构成滤波器组，可提高光束空间窄带滤波性能。该方法有利于克服激光工程中采用4f滤波带来的空间滤波器体积庞大与抽空耗能的缺点。     

用于ICF基准物理实验的子束激光系统优化设计

基于XG11激光装置实验平台建立了用于ICF基准物理实验的子束激光系统，采用软边光阑和空间滤波器组合的像传递技术实现了光束的空间整形和等像面传输，并利用Fresnel光束传输计算程序对系统进行了优化设计，分析了空间滤波器小孔尺寸以及软边光阑对光束波面传输的影响，并对优化设计结果进行了分析和讨论，所用方法和所得结论对高功率固体激光放大系统的设计具有一定应用意义。     

4×2×3阵列式放大器参数测量系统优化设计

采用软边光阑和多级空间滤波器组合技术实现了光束的空间整形和等像面传输，利用Fresnel光束传输计算程序对4×2×3阵列式放大器参数测量系统进行了优化设计，分析了空间滤波器中小孔尺寸对光束波面传输的影响，并对优化设计结果进行了分析和讨论，所用方法和所得结论对高功率固体激光放大系统的设计有应用意义。     

用逐次逼近迭代法分析含空间滤波器的多程激光放大系统的逆问题

基于Ｆｒａｎｔｚ－Ｎｏｄｖｉｋ（Ｆ－Ｎ）方程和广义惠更斯－菲涅耳衍射积分，提出了解决含空间滤波器的多程激光放大系统的逆问题的迭代算法，并作了数值计算了，所得的数值计算方法和有关结果可用于高功率多程激光放大系统的设计。     

4×2×3阵列式放大器参数测量系统优化设计

 采用软边光阑和多级空间滤波器组合技术实现了光束的空间整形和等像面传输，利用Fresnel光束传输计算程序对4×2×3阵列式放大器参数测量系统进行了优化设计，分析了空间滤波器中小孔尺寸对光束波面传输的影响，并对优化设计结果进行了分析和讨论，所用方法和所得结论对高功率固体激光放大系统的设计有应用意义。     

高功率激光近场诊断系统在线标定光源研制

针对高功率激光装置的特点，提出基于光纤激光的标准光源产生方法，以1053nm单模光纤激光为点源、以空间滤波器透镜为准直透镜获得了口径为300mm×300mm、不均匀性优于4％的均匀光源，成功实现了对神光Ⅲ原型装置近场诊断系统的在线标定。     

小宽带光谱色散匀滑光束传输特性研究

利用激光聚变研究中心自主开发的小宽带传输放大软件对小宽带光谱色散匀滑(SSD)光束进行具有"时间、空间、光谱分辨"的传输模拟,研究了SSD光束通过空间滤波器和自由空间的传输特性.给出了时间、空间、光谱的对应分布图,对比分析了SSD光束与非SSD光束的传输效应.研究结果对于合理设计SSD光束的发散角与空间滤波器小孔之间的匹配关系、选择适宜的调制频率,以及选择束匀滑色循环数等都有重要意义,同时对于光路设计特别是细光束自由传输距离的设计具有指导意义.     

拉曼链系统用空间滤波器设计的实验研究

进行了惯性约束聚变（ＩＣＦ）准分子激光拉曼链工程的基础研究工作。为给出拉曼链中所用空间滤波器的设计要求和可靠性,进行了详细的设计实验判断性研究。给出研究过程和结果,并对设计结论和优化方法进行了基础分析。还据实验结果讨论了适用于高功率激光系统的空间滤波器的设计中面临的焦距和滤波小孔孔径选择的不确定性、滤长和光束功率密度对选择小孔的影响等问题。     

激光气体分析仪中数字滤波器的设计

由于基于可调谐二极管激光吸收光谱（TDLAS）技术的激光气体分析仪的二次谐波信号中存在较大的系统噪声,本文利用有限长单位冲激响应（FIR）,提出了激光气体分析仪的二次谐波在线滤波方法。在分析FIR数字滤波器原理的基础上,利用MATLAB窗函数设计了适合本激光气体分析仪的数字滤波器。然后,将仿真的FIR数字滤波算法移植到激光气体分析仪嵌入式系统中。最后,比较了滤波前后二次谐波信号波形,说明了在激光气体分析仪嵌入式系统中采用基于FIR数字滤波器滤波算法的可行性。实验结果表明：FIR数字滤波器对一组二次谐波信号进行滤波的运算时间为230ms,滤波后的二次谐波信号波形获得了较好的去噪效果,能够满足激光气体分析仪对含有噪声的二次谐波信号进行平滑去噪的要求,且滤波算法结构简单、运算时间短、可移植性强。     

A Self-Diffraction Temporal Filter for Contrast Enhancement in Femtosecond Ultra-High Intensity Laser

We demonstrated a nonlinear temporal filter based on the self-diffraction(SD) process. Temporal contrast enhancement, angular dispersion and spectrum broadening properties of the SD process are investigated in experiment and simulation. Driven by spectral phase well compensated laser pulses with bandwidth of 28 nm,the filter produced clean pulses with a temporal contrast higher than 1010 and excellent spatial profile, the spectrum of which was smoothed and broadened to 64 nm. After implementing this filter into a home-made30 TW Ti:sapphire amplifier, temporal contrast of the amplified pulses was enhanced to 1010 within the time scale of-400 ps.     

Broadband spectral shaping in a Ti:sapphire regenerative amplifier

A birefringent crystal quartz plate of known thickness has been used as a spectral filter for spectral shaping in a Ti:sapphire regenerative amplifier. The spectral profile of the amplified pulse ejected from the regenerative amplifier was observed while adjusting the birefringent crystal plate in the cavity. By altering the gain spectrum, the bandwidth of the regeneratively amplified pulse was increased from 18 to 35 nm by using a 0.34-mm thick birefringent plate. The output pulse spectrum from the regenerative amplifier neared the bandwidth of the seed pulse. As a comparison, we used a coated filter outside the regenerative amplifier cavity, and the bandwidth of the regeneratively amplified pulse was stretched to 28 nm. When the bandwidth was stretched to 35 nm, the pulse was compressed to 35 fs.     

High-power top-hat pulses from a Yb master oscillator power amplifier for efficient optical parametric amplifier pumping

We demonstrate shaping of high-energy broadband Yb amplifier pulses for the generation of a (sub)picosecond top-hat temporal pulse profile that significantly improves pumping efficiency of an optical parametric amplifier (OPA). Phase-only modulation is applied by an acousto-optic programmable dispersion filter. This simple scheme is scalable to a high average power due to a relatively broad bandwidth of the Yb:CaF(2) gain medium used in the amplifier that supports a sub-150-fs transform-limited pulse duration. Additionally we show that OPA seeding with supercontinuum remains possible because top-hat-shaped pulses passed through a glass block recompress to ≈200 fs with minimum satellite production.     

OPCPA pump laser based on a regenerative amplifier with volume Bragg grating spectral filtering

A novel Nd:YVO₄−based regenerative amplifier system operating in the picosecond regime featuring a volume Bragg grating (VBG) as an intracavity spectral narrowing element is described. This compact amplifier provides pulses with duration of ∼85 ps operating at repetition rates ranging from single shot to 10 kHz. The VBG is used to passively tailor the pulse duration and achieve transform-limited pulses with 50 pm FWHM of spectral linewidth. A Gaussian output beam profile is obtained from the amplifier at all repetition rates. The intracavity VBG also guarantees a high spectral purity by efficiently preventing the build-up of out-of-band ASE. The spectral, spatial and temporal properties of this amplifier make it highly suitable for OPCPA pumping applications.     

Output irradiance uniformity in a single pass KrF amplifier

Using a model for the temporal and spatial variation of the saturation flux that considers the effects of temperature, fluorine burn-up and local E-fields on the quenching rates, it is found that long pulse operation of a KrF amplifier (τ_p > 500 ns) can result in spatial and temporal output irradiance uniformities greater than 80% across the aperture. Local E-fields are shown to be responsible for relatively large spatial saturation flux non-uniformities for short pulse KrF amplifier operation.     

Spatial chirp in Ti:sapphire multipass amplifier

The spatial chirp generated in the Ti:sapphire multipass amplifier is numerically investigated based on the onedimensional(1D) and two-dimensional(2D) Frantz–Nodvik equations. The simulation indicates that the spatial chirp is induced by the spatially inhomogeneous gain, and it can be almost eliminated by utilization of proper beam profiles and spot sizes of the signal and pump pulses, for example, the pump pulse has a top-hatted beam profile and the signal pulse has a super-Gaussian beam profile with a relatively larger spot size. In this way, a clear understanding of spatial chirp mechanisms in the Ti:sapphire multipass amplifier is proposed, therefore we can effectively almost eliminate the spatial chirp and improve the beam quality of a high-power Ti:sapphire chirped pulse amplifier system.     

Nd:glass diode-pumped regenerative amplifier,multimillijoule short-pulse chirped-pulse-amplifier laser

We have built a diode-pumped Nd:glass regenerative amplifier that is able to produce energies up to 20 mJ within a 470-fs pulse duration at a 1-Hz repetition rate. We obtained this amplifier by using specific intracavity components such as a phase mirror and a birefringent filter to generate a large spatial mode and a large spectral width.     

Spatial and temporal bilateral filter for infrared small target enhancement

This paper presents a spatial and temporal bilateral filter (BF) to detect target trajectories, by extracting spatial target information using a spatial BF and temporal target information using a temporal BF. Background prediction when it is covered by targets is the key to small target detection. In order to apply the BF to a small target detection field for this purpose, this paper presents a novel spatial and temporal BF with an adaptive standard deviation to predict spatial background and temporal background profiles, based on analysis of the blocks surrounding a spatial and temporal filter window. In order to discriminate between the edge or object regions with a flat background and the target region spatially and temporally, spatial and temporal variances of the blocks surrounding the filter window are calculated in a spatial infrared (IR) image and temporal profile. The spatial and temporal variances adjust standard deviations of the spatial and temporal BF. Through this procedure, spatial background and temporal background profiles are predicted, and then small targets can be detected by subtracting the predicted spatial background (and temporal background profile) from the original IR image (and original temporal profile) and multiplying spatial and temporal target information. To compare existing target detection methods and the proposed method, signal-to-clutter ratio gain (SCRG) and background suppression factor (BSF) are employed for spatial performance comparison and receiver operating characteristics (ROC) is used for detection-performance comparison of the target trajectory. Experimental results show that the proposed method has a superior target detection rate and a lower false-alarm rate.     

掺钛蓝宝石激光放大器中放大自发辐射效应研究

 给出了描述掺钛蓝宝石激光放大器的速率方程组，通过对放大介质内反转粒子数密度和放大自发辐射的时间和空间特性的数值计算与分析，提出可通过控制泵浦光脉冲和信号光之间的时间延迟来有效地抑制放大自发辐射对放大器增益的影响。     

多个超短脉冲相干叠加构成窄带平顶长脉冲的研究

利用超短脉冲放大过程中的光谱增益窄化效应以及标准具的滤波作用,提出了基于再生放大器的多脉冲相干叠加方案，并对该方案在多脉冲叠加阶段的工作原理进行了分析；在小信号增益区内，对多个超短脉冲相干叠加进行了理论分析和数值计算，数值模拟的结果表明，影响形成窄带平顶长脉冲的基本关系为子脉冲宽度、再生放大器中的损耗及其与振荡器的长度失配量对构成脉冲时间波形影响很大，而对其频谱影响很小；叠加脉冲个数、标准具的通带宽度对构成脉冲波形和光谱均有影响. 关键词： 超短脉冲 多脉冲叠加器 窄带平顶长脉冲 数值计算