共查询到20条相似文献,搜索用时 937 毫秒
1.
研究大气偏振光谱在太阳天顶角SZA、观测天顶角VZA和相对方位角RAA构成的观测几何变化时的特征。采用离散坐标法求解大气矢量辐射传输方程,结合真实大气环境与结构参数,以MODTRAN太阳参照光谱仿真大气层顶初始光谱,考虑下垫面反照、气溶胶垂直分层与成分混合比及痕量气体吸收的影响,仿真计算相对方位角为0°和90°时0.4~3 μm波段大气偏振光谱,丰富大气偏振光谱信息。仿真结果表明:(1)相对方位角为0°时,偏振度DoP和Q/I随SZA的变化分别呈“V形”和倒“U”形, U/I很微弱,量级低于10-7,V/I在任何观测几何下都很微弱;(2)晨暮时段,若太阳不在视场内,大气偏振度在波长0.51和2.75 μm附近为极大值,在1.5 μm附近为极小值。因此,在不同的观测几何条件下,选择相应的波段和偏振信号,将有利于实体目标探测。 相似文献
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A. S. Rokhmin N. V. Nikonorov A. K. Przhevuskii A. V. Chukharev A. M. Ul’yashenko 《Optics and Spectroscopy》2004,96(2):168-174
A partial polarization of luminescence in laser phosphate and silicate erbium-doped glasses was found to take place for the fundamental laser transition 4 I 13/2→4 I 15/2 (λ=1.55 μm) under excitation by linearly polarized laser radiation (532 and 790–990 nm). The shape of the luminescence spectrum depends on the wavelength of the exciting light and on the composition of the glass matrix. The degree of polarization of the luminescence depends on the spectral range of both the excitation and the detection, attaining a maximum of ~1%. The concentration dependence of the degree of polarization is studied. 相似文献
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报道了一个低阈值宽调谐、被动调Q、单谐振掺MgO的周期性极化铌酸锂晶体(PPMgLN)光学参量振荡器。利用被动调Q的Nd:YVO4激光器作为泵浦源,采用外腔结构,在室温下,实现了PPMgLN晶体的准相位匹配光学参量振荡。光参量振荡的阈值仅为0.27W(单脉冲能量4.5μJ、脉宽35ns);在泵浦光为1.35W(脉冲能量8.2μJ、脉宽35ns),PPMgLN周期为31μm时,获得了161.9mW,3.202μm脉冲激光输出;同时获得了98.5mW的1.594μm信号光输出,总的光光转化效率达到19.3%。通过改变晶体的周期,实现了闲频光3.13~4.19μm,信号光1.43~1.65μm的宽带可调谐激光输出。 相似文献
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The light reflection spectra and the magnetorefractive effect in the cobalt-based amorphous ribbons in the IR spectral region (λ = 2.5–25 μm) are studied. These amorphous alloys are characterized by the magnetoimpedance effect, which is enhanced after thermal and laser annealing. It is found that the magnetoimpedance and magnetorefractive effects correlate with each other. The magnetorefractive effect reveals a feature at λ = 15–20 μm and the change of sign in the wavelength region 20–25 μm. It is shown that, in the first approximation, the optical properties of the amorphous alloys in the IR spectral region can be explained on the basis of a modified Hagen-Rubens relation. It is found that the change in the reflection coefficient of amorphous metal films in the IR spectral region under action of a magnetic field is caused by the change in both their magnetic permeability and conductivity, which is caused by the degree of polarization of localized electronic states at the Fermi level. 相似文献
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积雪直接影响地表能量平衡和气候变化,与人类生产、生活息息相关,运用热红外偏振技术对新雪的发射光谱特性进行研究,可为热红外遥感监测雪的热辐射偏振特性定量研究提供基础,对加深对全球变暖理解及制定相应对策等具有重要意义。研究结果表明:波段对新雪热红外偏振特性影响很大,其偏振辐亮度(L)表现为:LCH1>LCH3>LCH4>LCH2,偏振亮温(T)表现为:TCH4>TCH1>TCH2>TCH3,在探测角50°偏振角90°处出现最大值而在探测角30°偏振角75°处存在最小值,利用CH3偏振亮温数据分析新雪热辐射偏振特性效果更优。探测角对新雪的偏振亮温影响极其显著,表现为:T10203005040,偏振度(P)表现为:P0>P30>P40>P20>P10>P50。偏振角对新雪亮温影响呈线性关系,在0~135°范围,每单位偏振角偏振亮温增加约0.003 ℃,这为新雪偏振亮温预测提供可能,在研究探测角对新雪偏振亮温影响时可忽略波段造成的差异。相对方位角对新雪的热辐射偏振特性影响不显著,这主要是由物质表面粗糙程度与组织结构差异导致,利用热红外偏振度对新雪的理化特性监测具有重要作用。 相似文献
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为了研究"猫眼"目标表面回波散射偏振特性,基于微面元理论建立了偏振双向反射分布函数模型,指出线偏振光在"猫眼"目标表面回波散射的偏振度与目标表面粗糙度、复折射率以及入射角、探测角有关。主要研究"猫眼"目标表面粗糙度对其回波散射偏振度的影响,利用Matlab仿真得到"猫眼"目标回波偏振度与目标表面粗糙度参数σ的关系曲线。选择经过不同砂纸打磨的硅片作为"猫眼"目标进行实验,当硅片表面均方根高度分别为0.067μm、0.554μm、0.726μm、1.651μm、1.893μm时,其表面回波散射偏振度的测量值依次为98.83%、98.16%、96.08%、94.91%、94.6%,表明"猫眼"目标回波散射的偏振度随其表面粗糙度的增大而减小。 相似文献
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N. Rehfeld U. Gerhardt E. Dietz 《Applied Physics A: Materials Science & Processing》1973,1(4):229-232
We use a 0.5 m Seya-Namioka monochromator and two gold plated cylindrical mirrors to set up an optical system which produces
a collimated beam of plane polarized, monochromatic radiation in the vacuum ultraviolet region. The two mirrors compensate
for the astigmatism of the Seya-Namioka monochromator, thereby increasing the spectral resolution drastically. The degree
of linear polarization is about 0.97–1.00 in the spectral region of 6–11.5 eV. 相似文献
10.
报道了基于掺氧化镁准周期极化铌酸锂(MgO:QPLN)的多光参量振荡器电场调谐特性理论与实验研究. 通过对电场调谐能力与极化结构参数间关联性的理论分析, 确定了高正负晶畴比MgO:QPLN电场调谐的可行性, 并模拟得到跨周期参量光输出波长与加载电压的关系曲线. 实验中通过对MgO:QPLN有效的电场加载, 实现了3.84 μm波段参量光的电场调谐, 频谱调谐带宽约6 nm, 调谐速率接近1 nm/kV, 进一步结合温度调谐, 实现了参量光宽谱段高精度的连续调谐. 所获得实验结果与理论模拟结果基本符合, 电场调谐在精度控制、快速响应方面相比于传统温度调谐更具技术优势. 相似文献
11.
Temperature sensing using 1.54 μm fluorescence at the transition between the energy levels4I15/2 (ground state) and4I13/2 generated in an erbium-doped fiber with 1.48 μm pumping is proposed. The fluorescence has a peculiar spectral profile that possesses two peaks around 1.530 μm and 1.552 μm wavelengths. The temperature-dependent fluorescence is investigated in the temperature range between -50°C and 90°C. The power ratio between the two peaks increases with an increase in temperature. The sensitivity of the ratio is 0.007/°C on average in the measured temperature range. The total fluorescence power and the absorption loss at λ = 1480 nm in the fiber decrease as the temperature increases. Optical fiber temperature sensing immune from the fluctuation in pumping power can be performed using the peak power ratio and/or the absorption loss. 相似文献
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基于近红外光谱(NIRS)技术和遗传算法-反向传播(GA-BP)神经网络建立模型,分析茶叶掺蔗糖样品的1~2.5 μm原始光谱数据的有效性及冗余度。固定样本数据,对模型的参数优化选择后建立茶叶蔗糖含量定量检测模型。将1~2.5 μm原始数据分1~1.7,1~1.3,1.3~1.7,1.7~2.5和2~2.2 μm。利用建立的模型对同一分辨率下的不同波段进行模型训练。预测结果表明,1~1.7和1~2.5 μm波段存在数据冗余。仅使用1.3~1.7或1.7~2.5 μm波段即可有效建立模型。预测模型对同一波段下的不同分辨率进行研究,从2 nm到20 nm改变分辨率,当波段范围为1~2.5 μm时,模型的R均介于0.9和0.95之间,且RMSEP也在1.7和2.1之间。当波段范围为1~1.7 μm时,模型的R均在0.9和0.93之间,且RMSEP也在1.95和2.25之间。结果表明,1~2.5 μm原始数据中确实存在波长范围和光谱分辨率的冗余。通过光谱特征分析和算法建模,可以显著提高光谱数据获取的有效性;对于茶叶中蔗糖含量的检测,可以采用更窄的波长范围和更低的光谱分辨率。 相似文献
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光谱波段是光学遥感器设计中需要考虑的一个重要指标。首先对探测海洋目标的反射式TDICCD光学遥感器需要选择的光谱波段进行分析,应用LOWTRAN 7软件对0.4μm~1.0μm波段的大气透过率进行了计算,同时对典型的海洋目标(如船体)、海水的光谱反射率及其对比度进行分析,最后对遥感器的入瞳辐射亮度和信噪比进行了估算。计算结果表明:遥感器光谱波段选择0.5μm~0.9μm波段,在入瞳辐射亮度和信噪比等方面优于选择0.5μm~0.8μm波段。这一结论为实用系统的波段选择提供了依据。 相似文献
14.
E. N. Kotlikov V. A. Ivanov V. G. Pogareva E. V. Khonineva 《Optics and Spectroscopy》2000,88(5):718-720
Results of studying the absorption coefficients and refractive indices of PbTe and GeTe films in the spectral range from 1 to 15 μm are presented. The optical constants of films were found by a technique that combines calculation methods and the presence of strong absorption bands in the spectra. The spectral intervals were determined where the film-forming materials under consideration offer promise in the production of interference coatings for the IR spectral region. 相似文献
15.
Yu. P. Sinichkin D. A. Zimnyakov D. A. Yakovlev I. A. Ovchinnikova A. V. Spivak O. V. Ushakova 《Optics and Spectroscopy》2006,101(5):802-810
The effect of the optical anisotropy of scattering media on the polarization state of scattered light is studied. The study is performed using a simple polarization method based on the comparison of the spectral composition of the co-and cross-polarized components of transmitted light measured for samples differently oriented with respect to the plane of polarization of probe linearly polarized light. The experimental results obtained are interpreted theoretically in terms of ordinary methods used in optics of birefringent media. Using rat skin as an example, it is shown that surface tissues can be characterized by a high degree of orientational order of the local optical axis of a medium within large areas (with a size of 5 mm or more), which manifests itself in macroscopic optical measurements. In such measurements in the spectral range 550–700 nm, whole rat skin behaves as a partially depolarized phase plate with a difference between the principal refractive indices Δn ≈ 0.00023. 相似文献
16.
Nguyen VD Akca BI Wörhoff K de Ridder RM Pollnau M van Leeuwen TG Kalkman J 《Optics letters》2011,36(7):1293-1295
We designed and fabricated an arrayed-waveguide grating (AWG) in silicon oxynitride as a spectrometer for spectral domain optical coherence tomography (SD-OCT). The AWG has a footprint of only 3.0 cm × 2.5 cm, operates at a center wavelength of 1300 nm, and has 78 nm free spectral range. OCT measurements are performed that demonstrate imaging up to a maximum depth of 1 mm with an axial resolution of 19 μm, both in agreement with the AWG design parameters. Using the AWG spectrometer combined with a fiber-based SD-OCT system, we demonstrate cross-sectional OCT imaging of a multilayered scattering phantom. 相似文献
17.
A long-wavelength IR broadband reflector is demonstrated using a high-index-contrast subwavelength grating based on a Si/SiO2 system. The field response has been computationally and experimentally verified to exhibit broadband reflectance in the spectral range of 13-16 μm with Δλ/λ=18.5% for reflectance >70%. The gratings exhibit incident field polarization dependence with an average extinction ratio of 1:1.6. 相似文献
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V. O. Gladyshev D. I. Portnov V. L. Kautz E. A. Sharandin 《Optics and Spectroscopy》2013,115(3):349-355
The results of experiments on observation of rotation of the plane of polarization of coherent laser radiation with wavelength λ = 0.632991 μm after propagation through a rotating optical disk made of TF3 glass with refractive index n = 1.71250 are analyzed. The experiments were conducted at angle of ray incidence on the flat disk surface ?0 = 60°, and the rotational speed of the disk was varied from 0 to 200 Hz in both directions. The results indicate that rotation of optically transparent, homogeneous, and isotropic dielectric causes rotation of linear polarization of the monochromatic electromagnetic plane wave by several tens of degrees. At a rotational speed of 3 Hz, the rotation of polarization reached Δφ = 70° for the vertical component of laser output polarization. The dependences of the angle of rotation of polarization and the degree of polarization of the rays on rotational speed are nonlinear and are attributed to the appearance of substantial anisotropic properties in a rotating dielectric. 相似文献
20.
石英波片偏光干涉谱的研究 总被引:1,自引:0,他引:1
根据石英晶体双折射率的色散特性,对石英波片的偏光干涉谱进行了理论分析和数值模拟,提出了一种石英波片延迟量和厚度的偏光干涉标定法。即由偏光干涉谱,可以得出石英波片在200~2000 nm宽光谱范围内的延迟量;通过对长波段的偏光干涉谱极值波长的精确判断,可以准确地计算出该石英波片的厚度。利用Lambda900紫外-可见-近红外分光光度计对一片石英波片的偏光干涉谱进行了测量。在波长精度为0.1 nm的情况下,测量的厚度精度为0.1μm。误差分析结果表明,通过提高光谱的最小分辨力及选择较长的光谱波段进行测量计算,可以有效地降低误差。 相似文献