30.4 nm波长SiC/Mg多层膜反射镜

波长30.4 nm的He-II谱线是极紫外天文观测中最重要的谱线之一,空间极紫外太阳观测光学系统需要采用多层膜作为反射元件。为此研究了SiC/Mg、B4C/Mg、C/Mg、C/Al、Mo/Si、B4C/Si、SiC/Si、C/Si、Sc/Si等材料组合的多层膜在该波长处的反射性能。基于反射率最大与多层膜带宽最小的设计优化原则,选取了SiC/Mg作为膜系材料。采用直流磁控溅射技术制备了SiC/Mg多层膜,用X射线衍射仪测量了多层膜的周期厚度,用国家同步辐射计量站的反射率计测量了多层膜的反射率,在入射角12°时,实测30.4 nm处的反射率为38.0%。     

Design of chirped Mo/Si multilayer mirror in the extreme ultraviolet region

The chirped Mo/Si multilayer mirror in the extreme ultraviolet region is designed to obtain sub-femtosecond pulses from high-order harmonics. Numerical simulations of temporal profile of the pulses are made for superposition of incident high-order harmonics and that of reflected ones by the chirped multilayer mirror.The normal incidence reflectivity and chirp in the wavelength range of 12.5 - 16.5 nm are 6.7% ±0.5%and-3617±171 as2, respectively. Simulation results indicate that the designed chirped multilayer mirror can be used for producing 104-as pulses.     

亚飞秒啁啾Mo/Si多层膜反射镜的设计、制作与性能检测

针对利用高次谐波获取亚飞秒脉冲的实验需求,设计制备了啁啾为－2 800 as2的啁啾Mo/Si多层膜反射镜.数值计算表明,采用所设计的啁啾多层膜反射镜可以获得86 as的脉冲.通过直流磁控溅射方法实现了Mo/Si多层膜样品的制备.在合肥同步辐射上进行了多层膜反射率的测量,在所设计的工作波长内,多层膜的平均反射率为5.6±2.3%.在考虑最上层Si的氧化作用后,对测量曲线进行拟合,得到的反射率曲线和膜层厚度分布分别与测试曲线和设计结果相吻合.     

4.48 nm正入射软X射线激光用Cr/C多层膜高反射镜的研制

针对4.48nm类镍钽软X射线激光及其应用实验,设计制备了工作于这一波长的近正入射多层膜高反射镜。选择Cr/C为制备4.48nm高反射多层膜的材料对,通过优化设计,确定了多层膜的周期、周期数以及两种材料的厚度比。模拟了多层膜非理想界面对高反射多层膜性能的影响。采用直流磁控溅射方法在超光滑硅基片上实现了200周期Cr/C多层膜高反射镜的制备。利用X射线衍射仪测量了多层膜结构,在德国BessyⅡ同步辐射上测量了在工作波长处多层膜反射率,测量的峰值反射率达7.5%。对衍射仪测量的掠入射反射曲线和同步辐射测量的反射率曲线分别进行拟合,得到的粗糙度和厚度比的结果相近。测试结果表明,所制备的Cr/C多层膜样品结构良好,在指定工作波长处有较高的反射峰,达到了设计要求。     

超高阈值Pick-off反射镜的研制

 采用水中抛光技术抛制了90mm×60mm×10 mm的K₉玻璃基片,表面粗糙度达1nm。在APS1504镀膜机上,摸索了电子束蒸发镀膜的最佳工艺条件,较稳定地在该超光滑玻璃表面上镀制了对波长1054 nm、入射角45°、反射率R≥99.5%的反射膜。膜层的抗激光损伤阈值可达26 J/cm²(1054nm, 1ns),镀膜后该玻璃基片反射波前可达l /10(p-v),最终制备了超高阈值Pick-off反射镜。     

磁控溅射制备横向梯度分布的Mo/Si周期多层膜

 采用磁控溅射方法在Si基板上镀制了横向梯度分布的Mo/Si周期多层膜。以X射线掠入射反射测量了横向梯度多层膜的膜系结构,在基板65 mm长度范围内,多层膜周期从8.21 nm线性减小到6.57 nm,周期梯度为0.03 nm/mm。国家同步辐射实验室反射率计的反射率测试结果表明：该横向梯度分布周期多层膜上不同位置,能反射在13.3~15.9 nm波段范围内不同波长的极紫外光,反射率为60%~65%。     

B4C/Mo/Si high reflectivity multilayer mirror at 30.4 nm

The B4C/Mo/Si high reflectivity multilayer mirror was designed for He-Ⅱ radiation (30.4 nm) using the layer-by-layer method. The theoretical peak reflectivity was up to 38.2% at the incident angle of 5°. The B4C/Mo/Si multilayer was fabricated by direct current magnetron sputtering and measured at the National Synchrotron Radiation Laboratory (NSRL) of China. The experimental reflectivity of the B4C/Mo/Si multilayer at 30.4 nm was about 32.5%. The promising performances of the B4C/Mo/Si multilayer mirror could be used for the construction of solar physics instrumentation.     

Design of the chirped Mo/Si multilayer mirror with SiC capping layer in extreme ultraviolet region

The design procedures were discussed in detail for a normal incident chirped Mo/Si multilayer mirror with Group Delay Dispersion (GDD) of ?3600 as² in the wavelength region of 13–17 nm. The GDD was calculated using an analytical approach by fitting the optical constants of the coating materials in the wavelength range of 12.8–17.2 nm, respectively. The final structure of the chirped mirror was obtained by using the simplex algorithm from the initial structure obtained by the genetic algorithm based on structure generated by a random generator. After considering the interfacial roughness and layers thickness deviation, the effects on the reflectivity and the GDD were discussed. It was found that the average reflectivity decreases from 5.98% to 4.22% and the average GDD decreases from ?3561.86 as² to ?3462.03 as², the vibration of GDD were larger than that of the reflectivity. The reflectivity was affected greatly by the 9th layer and the GDD was affected greatly by the 25th layer when each layer thickness changes ±0.2 nm. Compared with the GDD, the reflectivity was affected greatly by the layer thickness error.     

基于LED的非相干宽带腔增强吸收光谱技术

介绍了基于可见光波段高功率LED作为光源的高灵敏度宽带腔增强吸收光谱技术,该系统的探测灵敏度通过测量NO₂在472.3～479.3 nm范围内的吸收得到验证。将中心波长为457 nm的高功率LED发出的宽带非相干光耦合进入92.5 cm长、由两片高反射率透镜组成的高精度光学谐振腔内,使用CCD光谱仪(HR2000)测量透过光学腔的光强信号。腔镜在472.3～479.3 nm波长范围内的反射率通过O₂-O₂聚合物的吸收确定,实验测量了一系列低浓度NO₂气体样品,采用差分光谱拟合技术在80 s的平均时间内NO₂浓度反演的统计不确定性约为3.1 ppb(ng·mL-1)。     

500 nm带宽啁啾镜对的设计与应用

设计了中心波长在825 nm、有效带宽在600 nm～1100 nm的超宽带啁啾镜对,色散补偿量目标值为-100 fs2。配对设计的啁啾镜对有效抑制了单个啁啾镜的色散振荡,啁啾镜对色散振荡幅度的最大值为50 fs2,用设计制作的啁啾镜对进行色散补偿,用频率分辨光学开关测量装置对脉冲进行测量。将10.3 fs的超短脉冲通过0.5 mm厚的LBO晶体,色散效应导致脉冲展宽,半峰值处的全宽度为39.6 fs,实验结果表明,经过啁啾镜对一次色散补偿后的脉冲形状,半峰值处得全宽度为11.6 fs;脉冲经过2次补偿后,脉冲被压缩到10.7 fs。     

THE REFLECTIVE PROPERTIES OF BROADBAND OPTICAL MULTILAYERS

Binary multilayers with a certain kind of disorder may exhibit high reflection range over a very wide bandwidth. The dependencies of this bandwidth on the center wavelength, random layers sequence, refractive contrast of the coating materials, layer thickness errors and the angle of incidence have been studied numerically. Our simulations have shown that broadband reflectors can be designed for various applications. The reflective curves for staggered multilayers are also computed. The results show that the broadening effect of irregular multilayers is dominated by its degree of disorder. A broadband TiO₂-SiO₂ multilayer is fabricated. The measured width of the transmittance less than 1% for this multilayer covers 400 nm, from 700 to 1100 nm, which is just the tuning range of T_i: sapphire lasers.     

X射线W/B4C宽带多层膜的优化设计和制备

介绍了X射线宽带多层膜材料W和B4C的选定方法,依据伯宁(BERNING)公式确定出了在0.154 nm处X射线宽带多层膜的最佳膜对数。引入适当的评价函数,利用具有全局寻优特性且效率较高的遗传算法,在波长0.154 nm处优化设计出了掠入射角(θ)0.5°~0.9°范围内反射率值达到40%的宽角度宽带多层膜。宽带多层膜反射镜采用磁控溅射方法制备,并用X射线衍射仪对样品进行了检测,结果表明在掠入射角(2θ)1.0°~1.8°之间的相对反射率光谱曲线比较平坦。     

Throughput Measurement of a Multilayer-Coated Schwarzschild Objective Using Synchrotron Radiation

The throughput of a Schwarzschild objective using undulator synchrotron radiation was measured. Conventionally, the throughput was estimated from the squared reflectivity of one multilayer mirror and from the obstruction ratio. However, we evaluated the transmission ratio from the input and output photon flux using a precisely calibrated monochromatic beam from an undulator light source. It was found that the objective has a maximum throughput of 8.5% at a wavelength of 13.9 nm.     

Reflective phase shift measurement of the Mo/Si multilayer mirror in extreme ultraviolet region

The reflective phase shift of multilayer mirror is one important property required in EUV lithography and attosecond pulses experiments. The reflective phase shift of the periodic Mo/Si multilayer mirror was characterized by combining the reflectivity with total electron yield signal at the synchrotron radiation in Hefei. The multilayer was fabricated using direct current magnetic sputtering method. Using the wavelet transform approach, the period and each layer thickness were obtained, the small angle X-ray reflective data from X-ray diffractometer were fitted using these data as the mutilayer's initial structure. The TEY signal of the multilayer is coincided with the surface electron field of the multilayer. A thick Si layer was used to eliminate the effect of the multilayer's surface layer on the TEY signal. The retrieved difference in reflected phase from the incident phase was obtained combining the reflectivity with the total electron yield signal and it is similar with the calculated phase shift of the multilayer.     

Design and fabrication of highly dispersive semiconductor double-chirped mirrors

We report on the development of semiconductor double-chirped mirrors with the group delay dispersion of ?3,800 ± 100 fs² in the wavelength range between 1,058 ÷ 1,064 nm and reflectivity of 99.1 %. The simplified plane-wave reflection transfer method was used to design the mirror multilayer stack. The mirror contains an epitaxial AlAs/GaAs structure topped with a SiNx antireflective layer.     

Broadband and high efficiency metal multi-layer dielectric grating based on non-quarter-wave coatings as a reflective mirror

This article deals with designing a broadband and high efficiency metal multi-layer dielectric grating (MMDG) used to compress and stretch an ultrashort laser pulse. The diffraction characteristics of the MMDG are analysed by using the rigorous coupled-wave method. The multi-layer dielectric used as the reflective mirror is made up of non- quarter-wave coatings. Taking the diffraction efficiency of the 1 order as the value of merit function, the parameters such as groove depth, residual thickness, duty cycle, and reflective mirror are optimized to obtain broadband and high diffraction efficiency. The optimized MMDG shows an ultra-broadband working spectrum with the average efficiency exceeding 97% over 160 nm wavelength centred at 1053 nm and TE polarization. The optimized MMDG should be useful for chirped pulse amplification.     

波长1O64nm脉冲激光高阈值反射膜的研制

研究 Ｈｆ Ｏ２／ Ｓｉ Ｏ２ 高反射膜的制备工艺及其激光诱导损伤阈值的比较测试,分别采用了反应蒸镀 Ｈｆ Ｏ２、反应离子辅助蒸镀 Ｈｆ Ｏ２、反应离子辅助蒸镀金属 Ｈｆ 的源材料形成 Ｈｆ Ｏ２ 薄膜。采用这三种工艺制备了 Ｈｆ Ｏ２ ／ Ｓｉ Ｏ２ 高反射膜,在中心波长 １０６４ｎｍ 处,反射率 Ｒ≥９９．５％ ,其中反应蒸镀 Ｈｆ Ｏ２ ／ Ｓｉ Ｏ２ 高反射膜损伤阈值最高,可达 ６０ Ｊ／ｃｍ ２（１０６４ｎｍ ,５ｎｓ）。     

SiC/W/Ir multilayer-coated grating for enhanced efficiency in 50-100 nm wavelength range in Seya-Namioka mount

A broadband [SiC/W/Ir](2) multilayer coating was deposited onto a diffraction grating to enhance the grating efficiency in the 50-100 nm wavelength range in a Seya-Namioka mount. The holographic ion-beam etched grating had a laminar profile with 1200 lines/mm. The coating was designed by using the subquarterwave multilayer theory. The measurement results show that the efficiency in the -1st diffraction order is greater than 9.3% throughout the wavelength range of 50-100 nm, which is obviously higher than that of single-layer gratings with SiC, Ir, or Au coatings.     

High-reflectivity measurement with a broadband diode laser based cavity ring-down technique

A simple cavity ring-down technique employing a cw broadband diode laser is described for the reflectivity measurements of highly reflective mirrors. Due to the broad line width of the diode laser, the laser beam can be continuously injected into the ring-down cavity without tuning the cavity length or the laser frequency. Both Fourier- and time-domain data-processing approaches are developed to determine the reflectivity. In the Fourier domain, the amplitudes and phase shifts of the first and third harmonics of a periodic ring-down signal are measured as a function of the modulation frequency covering an appropriate range. The cavity decay time and the reflectivity of the cavity mirror are determined by minimizing a mean square variance containing both the amplitude and phase-shift error terms. On the other hand, in the time domain, the cavity decay time and the instrumental response time are determined simultaneously by fitting the measured waveforms of the cavity ring-down signals to a rigorous time-domain model via a multi-parameter fitting procedure. The reflectivity measurements are repeated at four cavity lengths and all the results obtained with both data-processing approaches are in excellent agreement. The reflectivity of cavity mirrors near 830 nm is statistically determined to be 0.99797 with an uncertainty less than 3×10^-5. PACS 07.60.Hv; 42.60.Da; 42.55.Px     

中心波长为28.5nm多层膜镜反射率测量

在“星光-Ⅱ”装置上以类Ne铬x射线激光作为标定源，以平场光栅谱仪为分光元件进行了285nm的Mo/Si多层膜反射镜效率测量.介绍了实验方法，给出了实验结果，本次研制的两块多层膜镜反射率分别为31%和9.6%. 关键词： x射线多层膜反射镜 反射率测量 x射线激光