High Spectral Resolution Mo/Si Multilayers Working at High Order Reflection

The high reflectance orders are used to improve the spectral resolution of Mo/Si multilayers. The multilayers for the first-, second- and third-order reflectance are designed and optimized, respectively. These multilayers are fabricated by using a directed current magnetron sputtering system, and the reflectivity is measured in an extreme ultraviolet range by synchrotron radiation. The experimental results show that the spectral resolution λ/Δλ（λ= 14 nm） increases from 24.6 for the first order to 66.6 for the third order.     

An effective reflectance method for designing broadband antireflection films coupled with solar cells

The solar spectrum covers a broad wavelength range,which requires that antireflection coating(ARC) is effective over a relatively wide wavelength range for more incident light coming into the cell.In this paper,we present two methods to measure the composite reflection of SiO2/ZnS double-layer ARC in the wavelength ranges of 300-870 nm(dualjunction) and 300-1850 nm(triple-junction),under the solar spectrum AM0.In order to give sufficient consideration to the ARC coupled with the window layer and the dispersion effect of the refractive index of each layer,we use multidimensional matrix data for reliable simulation.A comparison between the results obtained from the weighted-average reflectance(WAR) method commonly used and that from the effective-average reflectance(EAR) method introduced here shows that the optimized ARC through minimizing the effective-average reflectance is convenient and available.     

Experimental study of Fourier transform spectrometer based on MEMS micro-mirror

We propose a new Fourier transform spectrometer based on programmable microelectromechanical systems(MEMS) micro-mirror and an improved Michelson interferometer.The principle of the spectrometer is theoretically analyzed.A signal acquisition unit and an experimental set-up are designed.The spectrum of the polychromatic light source is obtained at a slantwise reflector angle of 0.238°.The spectrum is analyzed by this system within the near infrared.The experimental results show that the spectral accuracy is less than 3 nm,and the signal-to-noise ratio(SNR) is 18 dB.The spectral resolution is less than 16 nm.     

Molecular dynamic simulation of secondary ion emission from an Al sample bombarded with MeV heavy ions

Spluttering yields and kinetic energy distributions (KED) of Al atomic ions ejected from a pure aluminium sample under MeV silicon ion bombardment were simulated with the molecular dynamic method.Since the electronic energy loss Se is much higher than the nuclear energy loss Sn when the incident ion energy is as high as several MeV,the Se effect was also taken into consideration in the simulation.It was found that the simulated sputtering yield fits well with the experimental data and the electronic energy loss has a slight effect at incident ion energies higher than 4MeV.The simulated secondary ion KED spectrum is a little lower in the peak energy and narrower in the peak width than that in the experiment.     

Experimental Study of Effect of Medium Boundary on Light Distribution in Tissue Phantoms

An experimental method for investigating the effect of medium boundary on distributions of light in the biological tissue phantom intralipid is presented. Measurements of distributions of light in intralipid-10% suspensions at 633 nm are described, in which a narrow collimated beam is incident on the surface of the phantoms and into the different depths inside of the phantoms. The experimental results show that the effect of the boundary of the medium on the curves geometry of light distributions is trivial, but the effect on intensity of scattering light is obvious, the maximal relative change of the energy fluence reaches 53.8% and the position of the peak of the energy fluence curve has a shift of 1.1 mm in the reverse direction of incident light for the phantom with albedo a=0.998, and the effect of the boundary is decreased with the increase of the absorption coefficients of tissue phantoms. The experimental results were analysed by the diffusion theory. These studies will be helpful for further understandings of the relation between the boundary of biological tissue and the distribution of light in tissue.     

The spectral changes of partially coherent light focused by an apertured lens with chromatic aberration

The spectral changes of a partially coherent polychromatic light focused by an apertured lens with chromatic aberration are investigated. It is demonstrated that the spectrum in the focused field is different from that in the aperture. Comparing with the spectrum in the aperture, the spectrum in the focused field shifts to lower or higher frequency, which is defined as a spectral shift. The influence of chromatic aberration of the lens, the coherence of the partially coherent light in the aperture, the radius of the aperture, and the spectral width of the spectrum of the aperture on the spectral shift are investigated in detail. The numerical results show that these parameters affect the spectral shift noticeably.     

EXPERIMENTAL STUDY OF DIFFRACTIVE PROPERTIES OF WAVELENGTH-SIZED SINGLE GROOVE IN Si-Si3N4 SUBSTRATE

Experimental results are presented for the diffractive properties of wavelength-sized single groove in Si-Si₃N₄ substrate. The experimental results show that the diffraction of wavelength-sized single grooves in a non-perfectly conducting material is more complex than that of perfectly conducting material. The diffraction intensities change with the change of polarization angle of the incident light. The diffraction intensities for TM polarization light are larger as the groove width is larger. The diffraction intensities of TM polarization light decrease gradually and that of TE polarization light increase gradually when the groove width is close to the wavelength of the incident light. The variations of diffraction intensities are quite different not only for various grooves with different widths but also for different diffraction angles for the same groove. Although the intensity variation of each diffraction order has a very regular sinusoidal dependence on the polarization angles of the incident light, the variation phase of each diffraction order is not all the same.     

Research on the ultrafast fluorescence property of thylakoid membranes of the wild-type and mutant rice

A high yielding rice variety mutant (Oryza sativa L., Zhenhui 249) with low chlorophyll b (Chl b) has been discovered in natural fields. It has a quality character controlled by a pair of recessive genes (nuclear gene). The partial loss of Chl b in content affects the efficiency of light harvest in a light harvest complex (LHC), thus producing the difference of the exciting energy transfer and the efficiency of photochemistry conversion between the mutant and wild-type rice in photosynthetic unit. The efficiency of utilizing light energy is higher in the mutant than that in the wild-type rice relatively. For further discussion of the above-mentioned difference and learning about the mechanism of the increase in the photochemical efficiency of the mutant, the pico-second resolution fluorescence spectrum measurement with delay-frame-scanning single photon counting technique is adopted. Thylakoid membranes of the mutant and the wild-type rice are excited by an Ar^+ laser with a pulse width of 120 ps, repetition rate of 4 MHz and wavelength of 514 nm. Compared with the time and spectrum property of exciting fluorescence, conclusions of those ultrafast dynamic experiments are: 1) The speeds of the exciting energy transferred in photo-system I are faster than that in photo-system II in both samples. 2) The speeds of the exciting energy transfer of mutant sample are faster than those of the wild-type. This might be one of the major reasons why the efficiency of photosynthesis is higher in mutant than that in the wild-type rice.     

Study on validation method of visible imagery spatial resolution of imager on geostationary platform

Based on the analysis for the main elements of the total modulation transfer function (MTF) of imager on geostationary platform, the precise evaluation for its low spatial frequency spectrum has been achieved.Meanwhile, it is pointed out that the main cause of imagery spatial resolution lower than the designed value is the "slight defocus" of imager focal plane array (FPA). The validation method for visible imagery spatial resolution is proposed based on the analysis of defocused optical system model and edge-spread-function (ESF), the relative error is less than 7% after alleviating stray light effects. This method has been applied in the in-orbit ground testing of FY-2C geostationary meteorological satellite successfully.     

Study on validation method of visible imagery spatial resolution of imager on geostationary platform

Based on the analysis for the main elements of the total modulation transfer function (MTF) of imager on geostationary platform, the precise evaluation for its low spatial frequency spectrum has been achieved. Meanwhile, it is pointed out that the main cause of imagery spatial resolution lower than the designed value is the "slight defocus" of imager focal plane array (FPA). The validation method for visible imagery spatial resolution is proposed based on the analysis of defocused optical system model and edge-spread-function (ESF), the relative error is less than 7% after alleviating stray light effects. This method has been applied in the in-orbit ground testing of FY-2C geostationary meteorological satellite successfully.     

入射光单色性与界面粗糙度对多层膜反射性能的不同影响

多层膜界面粗糙度、入射光单色性对软X射线多层膜实际反射率均有影响。利用数学卷积积分,理论上推导出一个在入射光不同单色性下精确计算多层膜反射率的公式。利用给出的理论计算公式,简要分析了入射光不同单色性、不同界面粗糙度对Mo/Si多层膜反射率的影响。理论分析发现这两种因素对Mo/Si多层膜反射率影响完全不同:入射光低的单色性不但极大降低Mo/Si多层膜峰值反射率,而且使反射曲线的半峰全宽增加;而界面粗糙度是降低Mo/Si多层膜反射曲线上各点对应值,基本不改变Mo/Si反射曲线的半峰全宽,不改变反射曲线的形状。说明这两个因素在软X射线的长波段对多层膜反射性能的影响不同。     

Analysis on diffraction properties of the transmission phase grating

Diffraction properties of the transmission phase grating are analyzed in terms of the Fourier optics theory. The analysis results show that the diffraction intensity distribution of the transmission phase grating is closely related to the optical thickness of the grating and the wavelength of the incident light, and not only determined by the grating's period and slit width. For monochromatic incident light, more than 80% of the diffraction energy will concentrate to the first diffraction order under certain conditions. For white incident light, the energy of the first order of diffraction spectrum may be much higher than other orders. Based on these results, some possible applications of the transmission phase grating are discussed.     

Brewster Anomalies in Opaque Random Amorphous Multilayers a-Si:H/a-Si3N4+x:H

Reflectance anomalies of random amorphous multilayers are shown to be different dependence on the incident angle for s- and p-polarized light by simulation. Disappearance of these anomalies has especially been observed for p-polarized light propagation at a certain incident angle. It is shown that this incident angle is the extended Brewster angle defined for opaque materials. This phenomenon, i.e., the disappearance of reflectance anomalies, is the Brewster anomaly in random amorphous multilayers made with absorbent materials. Preliminary results of experiments are also presented.     

The determination of the true profile of XPS line by regularization method: I. Mathematical algorithm and numerical simulations

The resolution of XPS spectra is limited mainly by instrumental parameters like the spectral line width of exciting X-ray source and the finite energy resolution of the electron analyzer. A new algorithm of an inverse ill-posed problem has been proposed in which low resolution experimental XPS data can be enhanced by removing the instrumental functions. The regularization method with a special fast iteration algorithm is applied for determining the true profile line of a complex chemical compound if we know excitation and instrumental functions. This paper is structured as follows: (I) a mathematical algorithm is described and numerical simulation results are presented. (II) These algorithms have been applied to the poorly resolved C 1s spectrum of a poly-methyl methacrylate (PMMA) film studied by the conventional technique with monochromatic and polychromatic radiation. The resulting enhancement allows previously unresolved structure to be observed without any assumptions concerning number, position, shape of peaks and their ratio.     

Study of the frequency distribution of the fluorescent light induced by monochromatic radiation

The frequency distribution of the fluorescent light induced by monochromatic dye laser radiation was investigated. To exclude the influence of the Doppler width a strongly collimated atomic beam was used. The spectrum was measured by means of a piezoelectrically tunable spherical Fabry Perot. The interaction region between the laser light and the atomic beam was placed into the center of the interferometer. Thus the observed fluorescence spectrum was considerably more intense than in the case where the interferometer is used separately from the beam. The fluorescence spectrum was observed for different directions of polarization of the incident laser beam. In the case of weak excitation the spectrum consists of a sharp component essentially due to elastically scattered light. At high intensities a structure of three components is observed which is in agreement with theoretical predictions when circularly polarized light is used for excitation.     

Study of the frequency distribution of the fluorescent light induced by monochromatic radiation

The frequency distribution of the fluorescent light induced by monochromatic dye laser radiation was investigated. To exclude the influence of the Doppler width a strongly collimated atomic beam was used. The spectrum was measured by means of a piezoelectrically tunable spherical Fabry Perot. The interaction region between the laser light and the atomic beam was placed into the center of the interferometer. Thus the observed fluorescence spectrum was considerably more intense than in the case where the interferometer is used separately from the beam. The fluorescence spectrum was observed for different directions of polarization of the incident laser beam. In the case of weak excitation the spectrum consists of a sharp component essentially due to elastically scattered light. At high intensities a structure of three components is observed which is in agreement with theoretical predictions when circularly polarized light is used for excitation.     

时空混合调制型偏振干涉成像光谱仪干涉图获取模式研究

基于自行研制的时空混合调制型偏振干涉成像光谱仪（TSMPIIS）,提出了一种新的干涉图和光谱的获取模式,分析了干涉数据的排列方式,详细阐述了不同时刻获得的一系列干涉图组合的方法,并由TSMPIIS获得了单色光和复色光的干涉图.理想的干涉图和复原光谱充分显示了这种探测模式的优越性,如宽场、高探测灵敏度和高通量等. 关键词： 时空混合调制 偏振干涉成像光谱仪 获取模式     

Polychromatic intensity point spread function of a birefringent lens

We study the intensity point spread function (IPSF) of a uniaxial birefringent lens sandwiched between two linear polarizers under broadband illumination having flat-top spectral profile. The optic axis of the birefringent crystal is perpendicular to the lens axis. For monochromatic input illumination, a low-power birefringent lens offers enhanced resolution under parallel-polarizers configuration and apodization under crossed-polarizers configuration with a single focus as well. At a relatively high value of birefringence parameter, the proposed system behaves as a double-focus lens. The present communication uses a novel technique to study the effect of polychromatic illumination on the imaging characteristics of birefringent lenses. The studies reveal that the imaging characteristics of the low-power birefrigent lens does not deteriorate considerably under polychromatic illumination. However, for a polychromatic beam with large bandwidth, the imaging behavior of the system having high birefringence parameter deviates appreciably from that under strictly monochromatic illumination. The said system even loses its inherent bi-focal nature due to depolarization of polarized polychromatic light upon passage through the birefringent crystal.     

Spectral Anomalies in the Fraunhofer Diffraction Pattern

We study the spectral characteristics theoretically and experimentally in the Fraunhofer diffraction pattern formed by the diffraction of a spatially coherent, polychromatic light through a slit. It is found that the spectrum in some diffraction directions close to the singular direction is redshifted, compared to the spectrum of the incident polychromatic light, and blueshifted in other directions, and splits into two lines at the singular direction. We show that the experimental results are consistent with the theoretical expectations.     

A novel model for obtaining interferogram and spectrum based on the temporarily and spatially mixed modulated polarization interference imaging spectrometer

Based on the temporarily and spatially mixed modulated polarization interference imaging spectrometer (TSMPIIS) developed by us, a novel model for obtaining interferogram and spectrum is proposed. The interference data arrays acquired with this model are analyzed, and the method for combining a series of interferograms at different moments is illuminated in detail. Furthermore, the interferograms of monochromatic light and polychromatic light obtained by TSMPIIS are processed. The satisfying interferogram and reconstructed spectrums show the superiority of this detection model, such as wide field of view, high detection sensitivity and high throughput, etc.