Generation and characterization of a bright X-ray source using picosecond laser

High-resolution soft X-ray spectra of H-like and He-like ions were produced from laser irradiated silicon and aluminum targets. Plasma size was about 100 μm. X-ray spectra were analyzed to determine plasma parameters. We compared the line shape of resonance transitions and their intensity ratios to corresponding dielectronic satellites and the intensities of the inter combination lines of He-like ions, with the results of model calculations. Such comparison gave average values of the electron density N _e=(1?1.9)×10²¹ cm^?3 and the electron temperature T _e=460–560 eV for Si plasmas and about 560 eV for Al plasmas produced by the first and the second laser harmonics. According to our estimations, more than 10¹² photons were produced within the resonance line spectral width and in the solid angle 2π steredian during the total decay period.     

Measurement of distribution anisotropy of X-ray yield from a pyroelectric crystal surface

A technique for measuring the spatial distribution of X-rays generated by a pyroelectric source is developed and tested. Anisotropy in the spatial distribution of X-rays from the surface perpendicular to the pyroelectric axis of the lithium niobate crystal depending on the piezoelectric crystal axis orientation was detected. The result obtained shows the necessity of considering the effect of piezoelectric properties of pyroelectric crystals on X-ray generation processes.     

Bright spatially coherent wavelength-tunable deep-UV laser source using an Ar-filled photonic crystal fiber

We report on the spectral broadening of ~1 μJ 30 fs pulses propagating in an Ar-filled hollow-core photonic crystal fiber. In contrast with supercontinuum generation in a solid-core photonic crystal fiber, the absence of Raman and unique pressure-controlled dispersion results in efficient emission of dispersive waves in the deep-UV region. The UV light emerges in the single-lobed fundamental mode and is tunable from 200 to 320 nm by varying the pulse energy and gas pressure. The setup is extremely simple, involving <1 m of a gas-filled photonic crystal fiber, and the UV signal is stable and bright, with experimental IR to deep-UV conversion efficiencies as high as 8%. The source is of immediate interest in applications demanding high spatial coherence, such as laser lithography or confocal microscopy.     

Self-optimization of optical confinement in an ultraviolet photonic crystal slab laser

We studied numerically and experimentally the effects of structural disorder on the performance of ultraviolet photonic crystal slab lasers. Optical gain selectively amplifies the high-quality modes of the passive system. For these modes, the in-plane and out-of-plane leakage rates may be automatically balanced in the presence of disorder. The spontaneous optimization of in-plane and out-of-plane confinement of light in a photonic crystal slab may lead to a reduction of the lasing threshold.     

Angular divergence of forwards and backwards emission from an FIR laser,using a pyroelectric vidicon

The angular divergence of FIR radiation at 66 μm and 116 μm from a D₂O cell pumped by single mode pulsed CO₂ laser is obtained, in both forward and backward directions. The forward emission, in similarity with SRS at other wavelengths, emerges with divergence close to the diffraction limit in some cases. The backward emission, probably dominated by ASE, has a greater divergence and at high filling pressures appears to break up into speckles.     

XBIC using a laboratory X-ray source

Results from using the current method, in which a current is induced by a focused X-ray beam (XBIC = X-ray beam induced current) on a laboratory source are presented. It is shown that by reducing the X-ray probe sizes and improving the resolution, there is a gain in contrast increase for obtained images of grain boundaries in a crystal.     

Sequential confocal and multiphoton laser scanning microscopy using a single photonic crystal fibre based light source

A novel approach that simplifies the laser source requirements for confocal and multiphoton laser scanning (CLSM and MPLSM) using the novel dispersion properties of photonic crystal fibre (PCF) is reported. By tuning the fs-pulsed Ti:Sapphire laser to the zero dispersion wavelength of the PCF, the spectral and temporal properties of the source are largely unaffected and hence this source can easily be used for MPLSM. Conversely, by tuning the Ti:Sapphire laser emission wavelength by less than 10 nm to anomalously pump the PCF, the resultant white-light supercontinuum source can perform CLSM. Sequential CLSM and MPLSM of a double-labelled guinea pig detrusor (smooth muscle layer) specimen is described. PACS 87.64.Tt; 87.64.Vv; 42.65.Ky     

Continuous wave photonic crystal laser in ultraviolet range

It is shown that photonic band-gap (PBG) structures have great potential for the development of widely tunable continues wave and/or mode-locked ultrashort-pulse all-solid-stale lasers in UV and optical ranges. The basic idea is to decrease the laser threshold via inhibition of radiative decay of an upper laser level by embedding an active medium into spatial structure having PBG at the frequency of laser transition. This technique provides favorable conditions for coherent suppression of the excited state absorption crucial for short-wavelength solid-state lasing. It also resolves the laser gain dilemma, providing combination of high emission cross-section and large population inversion. Different designs of 2D and 3D photonic crystal laser are proposed.     

X射线微光刻的常规X射线光源实现方法

叙述了利用固体靶X射线光源实现X射线微光刻的方法,给出了X射线掩膜、抗蚀剂及X射线曝光的工艺过程和实验结果.     

用X-pinch对双丝Z箍缩进行轴向X射线背光照相

利用PPG-1脉冲电流源(400 kA, 100 ns), 同时驱动X-pinch和双丝Z箍缩负载. 用X-pinch作为X射线源, 对双丝Z箍缩进行了轴向背光照相的初步实验. 得到了双丝Z箍缩在r-θ 平面上随时间演化的图像, 观察到了丝阵Z箍缩所有早期过程, 包括丝芯膨胀、冕层等离子体产生、等离子体向丝阵中心的运动、先驱等离子体形成. 利用阶跃光楔滤片, 对上述背光图像进行了等离子体质量面密度的标定, 首次得到了在r-θ平面上双丝Z箍缩等离子体质量面密度的时空分布图像.     

Curved crystal analysis using a triple-crystal X-ray spectrometer

A Bragg crystal spectrometer using cylindrically curved crystals is designed to focus a divergent X-ray beam. The spectral resolution and precision of focus is determined by the quality of the concavely curved crystal. The analysis of the quality of the crystal was done using a triplecrystal X-ray spectrometer, comparing parallel and antiparallel X-ray scans of the third curved crystal, determining flaws resulting from the bend. Topics discussed include the derivation of the crystal's quality, conditions of alignment for the Bragg reflection, and X-ray beam width contributions to the FWHM. Organic and inorganic crystals with varying values of Bragg angles are used.     

相位型波带板应用于大尺度X射线源成像的分析与模拟

针对大尺度物体的keV-X射线高分辨成像,分析了相位型菲涅耳波带板(FPZP)对物平面1mm区域内点源的成像,确定像的空间分布具有不变性,提出了一种FPZP对扩展光源成像的计算方法.使用这一方法,模拟了放大倍数为10的典型实验条件下最外环宽0.35 μm的FPZ对扩展单色光源的成像.结果表明,随着扩展光源尺度的增加,像的对比度降低.FPZP的负1级和0级衍射是导致像的背景增强和对比度降低的主要因素,并相应导致成像对物方的空间分辨能力下降.对于强度空间分布为正弦调制、对比度为1的1mm尺度方形光源,像的对比度低于0.4,物方分辨能力为0.75 μm.     

利用X射线激光进行激光等离子体射流的诊断

射流是激光惯性约束聚变(ICF)、天体物理学等领域中一种普遍存在的非线性现象.在实验室对射流现象进行模拟、诊断等方面的研究对于理解ICF、天体物理中的相关现象具有重要参考价值.采用纳秒激光辐照特殊形状的圆孔靶产生等离子体射流,利用波长为13.9nm的X射线激光作为光源对特定时刻的射流进行阴影成像,获得了清晰的射流阴影图像,与理论模拟结果定性一致. 关键词： 射流 X射线激光 等离子体诊断     

Mass-limited Sn target irradiated by dual laser pulses for an extreme ultraviolet lithography source

A thin Sn film was investigated as a mass-limited target for an extreme ultraviolet (EUV) lithography source. It was found that those energetic ions that are intrinsic with the mass-limited Sn target could be efficiently mitigated by introducing a low-energy prepulse. High in-band conversion efficiency from a laser to 13.5 nm EUV light could be obtained using an Sn film with a thickness down to 30 nm when irradiated by dual laser pulses. It was shown that the combination of dual pulse and inert Ar gas could fully mitigate ions with a low ambient pressure nearly without the penalty of the absorption of the EUV light.     

Tunable frequency-controlled laser source in the near ultraviolet based on doubling of a semiconductor diode laser

Continuously tunable ultraviolet laser radiation at 397 nm was generated by doubling the output of a semiconductor diode laser. The fundamental radiation was provided by a 150 mW AlGaAs laser diode injected by a low-power AlGaAs laser diode which was frequency stabilized by optical feedback using a new scheme of a miniature external cavity. Second-harmonic generation was produced in a lithium-triborate crystal placed in a compact enhancement cavity. The fundamental radiation was used for sub-Doppler spectroscopy of the Ar I 4s ³ P ⁰ ₀–4p ¹ P ₁ transition at 795 nm; the second-harmonic radiation was used for spectroscopy of the Ca II 4² S _1/2–4² P _1/2 transition at 397 nm.     

A positron source using an axially oriented crystal associated to a granular amorphous converter

A non-conventional positron source using the intense γ radiation from an axially oriented monocrystal which materializes into e⁺e^- pairs in a granular amorphous converter is described. The enhancement of photon radiation by multi-GeV electrons crossing a tungsten crystal along its <111> axis is reported. The resulting enhancement of pair production in an amorphous converter placed 2 meters downstream, is also reported. Sweeping off the charged particles from the crystal by a bending magnet upstream of the converter allows a significant reduction of the deposited energy density. Substituting a granular target made of small spheres for the usual compact one, makes the energy dissipation easier. The deposited energy and corresponding heating are analyzed and solutions for cooling are proposed. The configurations studied here for this kind of positron source allow its consideration for unpolarized positrons for the ILC.     

闪光X射线照相光源的发展

闪光X射线照相是利用加速器产生的短脉冲X射线对快速运动的致密客体进行透视照相的技术。概述了闪光X射线照相对X射线的性能要求;回顾了闪光X射线照相及其加速器的发展历程;分析了闪光X射线照相用加速器的发展方向。     

A low debris laser plasma soft X-ray source

Low debris laser plasma soft X-ray source is of great importance to micro-lithography and microscopy. In this paper, a 1.06 μm YAG laser with 2 J energy, 10 ns duration is employed to irradiate a CO₂ cryogenic target. Soft X-ray spectra from the CO₂ cryogenic target are obtained. Experimental results of debris measurement from both CO₂ cryogenic and Cu targets demonstrate that the light source based on the CO₂ cryogenic target shows great improvement over conventional metal targets in debris reduction.     

BBO晶体四倍频全固态小功率紫外激光器

 利用KTP晶体和BBO晶体,进行了激光二极管泵浦的Nd:YVO₄声光调Q激光脉冲四倍频实验。在不同绿光功率入射时,获得光束的束腰半径和紫外转换效率的依赖关系:当绿光功率为1.10 W,束腰半径为12.4 μm时,得到了210 mW的准连续266 nm紫外脉冲输出,四倍频转换效率为19.1%。实验还对紫外远场光斑分别在o光振动面和e光振动面内进行分析,指出了BBO晶体在该两平面内不同的倍频接受角是造成椭圆形紫外光斑和主光斑附近明暗条纹的主要原因。     

BBO晶体四倍频全固态小功率紫外激光器

利用KTP晶体和BBO晶体,进行了激光二极管泵浦的Nd:YVO4声光调Q激光脉冲四倍频实验。在不同绿光功率入射时,获得光束的束腰半径和紫外转换效率的依赖关系:当绿光功率为1.10 W,束腰半径为12.4 μm时,得到了210 mW的准连续266 nm紫外脉冲输出,四倍频转换效率为19.1%。实验还对紫外远场光斑分别在o光振动面和e光振动面内进行分析,指出了BBO晶体在该两平面内不同的倍频接受角是造成椭圆形紫外光斑和主光斑附近明暗条纹的主要原因。