DF激光器光栅选线实验研究

基于闪耀光栅的分光原理,利用小型直流放电驱动化学激光器,在平凹稳定腔内插入闪耀光栅,建立了选择激光器光栅谱线的实验装置.实验中共获得了14条谱线,测量了每条谱线的功率,计算了波长,分析了选线后谱线条数减少、谱线功率降低的原因.该装置尺寸小,使用比较方便,可以满足连续波DF化学激光器性能研究的需要.     

在HL－1M装置上用弯晶谱仪测量离子温度

本文叙述在ＨＬ－１Ｍ装置上用弯晶谱仪获取Ｆｅ的类Ｈｅ离子谱，用谱线的多谱勒加宽测量等离子体的离子温度，得到的等离子体ＨＬ－１Ｍ装置离子温度为５００—８００ｅＶ。     

1.31μm附近CO2的高灵敏度吸收光谱

采用可连续调谐半导体二极管激光器作为探测光源,将长程多通池吸收光谱、波长调制和谐波探测技术相结合,建立了一套具有高检测灵敏度和高分辨率的测量气态分子光谱及进行微量分析的研究装置.可以测量6.67×102Pa下～10-27 cm-1·(molecule·cm-2)-1的强度,最小可探测吸收达到～10-8.并利用该装置测量了CO2气体在1.31 μm附近的近红外吸收光谱,并用最小二乘法拟合实验数据获得了这一波段谱线的参数.同时测量的谱线参数与HITRAN数据库相比,发现15条数据库上没有报道的弱谱线.     

从大气压到超低气压范围的氦等离子体发射光谱的基本特性

采用三种实验装置(介质阻挡放电装置、空心阴极放电装置和彭宁放电装置)分别测量了不同压强范围内氦等离子体的发射光谱。通过对氦等离子体发射光谱的分析,已观察到一个共同的特点,就是在三种放电条件下产生的氦等离子体中31P1→21S0的谱线强度总是最强,可以推测亚稳态氦原子的含量相当显著,但不同的装置也有不同的特点,介质阻挡放电装置能够产生准辉光放电,谱线中氦原子的谱线强度很低,而空心阴极放电与彭宁放电装置能够产生稳定均匀的等离子体,且发射足够强的光辐射。我们已对所拍摄的光谱的谱线都进行了辨认,所有结果表明原子发射光谱分析法是研究不同条件下氦等离子体状态的一种十分有效的手段。     

傅立叶变换激光腔内吸收光谱方法研究吸收谱线的强度与线形

在原有傅立叶变换激光腔内吸收光谱实验装置的基础上,利用信号差分方法减少了光强波动对实验干涉谱图的影响,改善了信噪比.通过对大气中氧气在760nm处的吸收谱线的绝对强度测量,验证了该方法的定量测量能力.在不同压力条件下对磷烷v=6伸缩局域模泛频吸收谱带进行了测量,获得了其谱线的自压力加宽和自压力线移参数.     

10-2～105 Pa气压范围的氦等离子体光谱分析

采用三种实验装置(介质阻挡放电装置、空心阴极放电装置和彭宁放电装置)分别测量了不同压强范围内氦等离子体的发射光谱.通过对氦等离子体发射光谱的分析,已观察到一个共同的特点,就是在三种放电条件下产生的氦等离子体中31P1→21S0的谱线强度总是最强,可以推测亚稳态氦原子的含量相当显著,但不同的装置也有不同的特点,介质阻挡放电装置能够产生准辉光放电,谱线中氦原子的谱线强度很低,而空心阴极放电与彭宁放电装置能够产生稳定均匀的等离子体,且发射足够强的光辐射.我们已对所拍摄的光谱的谱线都进行了辨认,所有结果表明原子发射光谱分析法是研究不同条件下氦等离子体状态的一种十分有效的手段.     

Ba原子6s6p1P1←6s6s1S0跃迁的光腔衰荡光谱

建立了一套光腔衰荡原子束吸收光谱测量装置,并对Ba原子的6s6p¹P₁←6s6s¹S₀吸收谱线用光腔衰荡光谱方法进行了测量,得到了Ba原子在553.548nm不同温度下的吸收谱线线型.实验结果表明,该装置测量吸收灵敏度达到6×10^-7. 关键词： 光腔衰荡 吸收光谱 Ba原子     

积分光谱法测量塑料薄膜厚度研究

在谱带朗伯定律概念的基础上,通过分析光束在透过塑料薄膜时光强所发生的变化,提出了谱带积分透过率定义并建立基于谱带积分透过率的薄膜厚度测量模型。采用不同厚度的聚丙烯薄膜作为实验对象,使用光谱仪测量了其光谱透过率。按上述模型拟合了薄膜厚度与谱带积分透过率关系式。使用500K理想黑体,分析了基于此方法研制新型宽谱带塑料薄膜厚度在线检测装置的可行性。实验结果表明：使用积分光谱法可以较高精度的测量塑料薄膜厚度。基于此方法研制的塑料薄膜厚度在线检测装置,有望解决使用双单色光对比法测薄膜厚度时存在的准确性低、通用性差的问题。     

1．3μm附近CO2的高灵敏度吸收光谱

采用可连续调谐半导体二极管激光器作为探测光源,将长程多通池吸收光谱、波长调制和谐波探测技术相结合,建立了一套具有高检测灵敏度和高分辨率的测量气态分子光谱及进行微量分析的研究装置.可以测量6.67×102Pa下～10-27 cm-1·(molecule·cm-2)-1的强度,最小可探测吸收达到～10-8.并利用该装置测量了CO2气体在1.31 μm附近的近红外吸收光谱,并用最小二乘法拟合实验数据获得了这一波段谱线的参数.同时测量的谱线参数与HITRAN数据库相比,发现15条数据库上没有报道的弱谱线.     

HL-1M装置等离子体的MARFE现象

在HL-1M装置上用分子束注入等离子体的气体加料方法提高了等离子体的电子密度。当线平均电子密度从 4× 10 13cm-3 上升到 7× 10 13cm-3 时 ,利用多道辐射损失测量系统测量到来自等离子体边缘的非对称辐射现象。在强场侧等离子体辐射损失功率密度大大高于弱场侧而线平均电子密度、OⅥ杂质谱线和Hα 谱线明显增加     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Research on beamforming method for dual-line array with space mismatch between the two line arrays

The performance of port/starboard discrimination of dual-line array will be seriously degraded when the space between the two line arrays of the dual-line array is mismatched. The directivity function of the delay-sum and delay-subtract beamforming is deduced and the port/starboard discrimination of the delay-sum and delay-subtract beamforming is also studied both under the ideal status and the status under which the space between the two line arrays of the dual-line array is mismatched. Analysis results show the delay-subtract beamforming has better performance of port/starboard discrimination. At last, the sea trial results demonstrate the theoretical results.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Retrieval of ultraviolet skylight radiances and O3 slant column densities from balloon-borne limb spectrometer

With a novel light-weight and absolutely calibrated ultraviolet （UV） spectrometer, UV skylight radiances and O3 slant column densities are measured by balloon-borne limb measurements in Xinjiang area, China. UV skylight radiances measured at the height of 31 km are compared with the results from Modtran in the wavelength range from 290 to 420 nm. O3 slant column densities are derived from radiance spectra in the Huggins bands （320 - 335 nm） using differential optical absorption spectroscopy method. And the parameter exhibits a good correlation with the same value simulated by radiative transfer model （Tracy）. The O3 profile simultaneously measured by an O3 sonde is used as input in Tracy calculations. The O3 sonde is launched on the same balloon.     

Design optimization of highly sensitive LSPR enhanced surface plasmon resonance biosensors with nanoholes

For breaking through the sensitivity limitation of conventional surface plasmon resonance (SPR) biosensors, novel highly sensitive SPR biosensors with Au nanoparticles and nanogratings enhancement have been proposed recently.But in practice, these structures have obvious disadvantages.In this study, a nanohole based sensitivity enhancement SPR biosensor is proposed and the influence of different structural parameters on the performance is investigated by using rigorous coupled wave analysis (RCWA).Electromagnetic field distributions around the nanohole are also given out to directly explain the performance difference for various structural parameters.The results indicate that significant sensitivity increase is associated with localized surface plasmons (LSPs) excitation mediated by nanoholes.Except to outcome the weakness of other LSP based biosensors, larger resonance angle shift, reflectance amplitude, and sharper SPR curves' width are obtained simultaneously under optimized structural parameters.     

Polymer gratings based on photopolymerization for low-order distributed feedback polymer lasers

Novel polymer distributed feedback(DFB)gratings are fabricated based on photopolymerization to reduce lasing threshold of polymer lasers.A photopolymer formulation sensitive to 355-nm ultraviolet(UV)light is proposed for the fabrication of polymer gratings and it can be used to form polymer films by spin-coating process.A very low surface-relief depth ranging from 12.5 to about 1.0 nm has been demonstrated with a refractive-index modulation of about 0.012.The experimental results indicate that such polymer gratings have promising potentials for the fabrication of low-order DFB organic semiconductor lasers.