Optimal corrections of the optical defects by minimizing the caustic merit function

Summary Until recently corrections of the defects of the optical system in the lens design such as a triplet lens system have been based on classical conceptions of the image formation through refraction surfaces of the system, or based on the third-order Siedel's aberration coefficient. This paper continues emphasizing the use of the caustic merit function, that describes the spread of the caustic surfaces from an ideal image point. This caustic merit function is then used to optimize a triplet lens. Results show that optimizing the caustic merit function is still the fastest and an effective method in the optical design in the case of plane waves.     

Theoretical analysis of the performance of a gravity-controlled solar concentrator

Summary We here analyse the geometrical concentrations and the energy gathered by the fixed collector of a solar concentrator, whose curvature is determined by the force of gravity and by a distribution of varable density. These quantities are directly compared with those of concentrators controlled merely by gravity, that is the curvature of which s determined only by the force of gravity. A more realistic analysis than one would have from the energy presumably gathered by the collector during the ten years from 1964 to 1973 is achieved, by utilizing the data on solar radiation collected at the Geophysical and Geodetical Institute of Genoa University in the city of Genoa (44^o 24′ 53″ N latitude, 55 m above sea-level).

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Riassunto Si analizzano le concentrazioni geometriche e l'energia raccolta dal collettore fisso di un concentratore solare, con curvatura determinata dalla forza di gravità e da una distribuzione di densità variabile, confrontandole direttamente con quelle di concentratori puramente gravitazionali, con curvatura determinata cioè dalla sola forza di gravità. Un'analisi più realistica di quella che presumibilmente sarebbe stata l'energia raccolta dal collettore nei dieci anni, dal 1964 al 1973, è fatta utilizzando i dati di insolazione rilevati dall'Istituto Geofisico e Geodetico dell'Università di Genova presso la città di Genova (44^o 24′ 53″ latitudine nord, quota 55 metri sul livello del mare).

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Резюме В этой работе мы анализируем геометрические концентрации и энергию, собранную фиксированным коллектором солнечного концентратора, кривизна которого определяетяется силой гравитации и распределением переменной плотности. Полученные результаты непосредственно сравниваются с результатами для концентраторов, контролируемемых только гравитацией, т.е. кривизна которых определяется только силой травитации. Выполняется более реалистческий анализ, чем анализ, проведенный ранее, собранной энергии коллектором в течение десяти лет с 1964 по 1973 годы. При анализе использовались данные по солнечной радиации, собранные Геофизическим иГеодезическим Институтом Университета Генуи (44^o 24′ 53″ северной широты, 55 метров вьше уровня моря).

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A study completed within the Finalized Energy Program of C.N.R.

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About to graduate at the Istituto di Scienze Fisiche of the Genoa University.     

Optimisation of the light transmission and irradiance distribution of an aspherical lens for 3-D time-of-flight sensors

The irradiance distribution and power transmission in a 3-D sensor, which is based on the principle of time-of-flight (TOF) and uses modulated active illumination, should be optimised because of a large light energy damper and low signal-noise ratio at the receiver detector array. A numerical design of a spherical–aspherical lens with large numerical aperture has been presented to generate a homogeneous irradiance on a measure object from an LED source. Based on the design and analysis of reflection loss, optimisations have been taken to maximise the optical transmittance of the lens. The results show that the total transmittance can be improved by optimising the shape and material of the lens.     

色散渐减光纤组成的环形镜对高阶孤子的理想压缩

利用数值模拟方法证明,采用色散渐减光纤组成的非线性光纤环形镜不仅可压缩高阶光孤子,而且能有效地消除压缩后脉冲的底座、提高光脉冲的输出能量.研究表明,对于一确定的色散渐减光纤,只要选取不同环形镜长度,即可对不同阶数的高阶孤子进行理想压缩.且孤子阶数越高,所需最佳环形镜长度越短、压缩后光脉冲的峰值强度越大、能量透射率越低.研究同时发现,环形镜的功率分束比存在一最佳值,在此值下所得压缩后的光脉冲不仅具有较大的峰值及能量透射率,且不含底座.     

太阳能材料CuInS2的晶体结构、电子和光学特性

用全电势线性缀加平面波法加局域轨道方法调查了黄铜矿半导体CuInS2的结构、电子和光学特性。我们计算的带隙0.17 eV是直接的,其它实验和理论也表明这种材料有一个直接带隙。在 In 4d和S 3p轨道之间有相当强的杂化,构成了(InS2)4-阴离子。我们计算的反射率光谱,介电函数的实部和虚部,消光系数和折射率和实验结果取得了很好的一致。     

Optimal resolution with extreme depth of focus

When the focal depth is required to be much larger than the wavelength, λ, the effective NA of the beam with optimal resolution is much less than unity. An aperture that is much larger than this beam's footprint is then of no consequence. Such beams that maximize the mean encircled energy fraction within a cylindrical focal region are shown to depend on only a single parameter, ω, that is proportional to the ratio of the square of the cylinder's radius to the product of its length and λ. A linear combination of Hermite– or Laguerre–Gaussian modes is used to represent these fields in two and three dimensions, respectively. For small ω, the results are compared both to asymptotic expansions and to optimal Gaussian and Bessel–Gauss beams.     

Enhanced efficiency of the luminescent solar concentrator fabricated with an aqueous layer

A novel method for preparing a luminescent solar concentrator(LSC) with fluorescent aqueous layer sandwiched between two pieces of flat glass is developed. By this method, an aqueous layer concentrator with a size of 78×78×7(mm) is fabricated. After coupled with silicon solar cell, the concentrator shows a power conversion efficiency of 3.9%, about 30% higher than that of the same sized laminated glass concentrator employing the same dyes. Furthermore, the measured efficiency almost reaches the calculated limit of the aqueous layer LSC. This kind of aqueous layer LSC offers a potential application in the buildingintegrated photovoltaics.     

圆形高斯镜平凹腔腔镜倾斜时光场模式分析

运用边界元素法把圆形高斯镜平凹腔的自再现模的衍射积分方程转化为有限阶矩阵方程。计算了谐振腔在理想情况和高斯反射率平面输出镜倾斜情况下基模的场强分布、相位分布和本征值。研究表明,腔镜倾斜使激光场模式分布沿发生倾斜的方向向镜边缘偏移,而且在腔镜倾斜较严重时模式分布发生畸变,不再是对称的拉盖尔-高斯基模分布。基模本征值随倾斜角增大而变小,光束远场分布变差。减小高斯分布反射率的膜斑半径,则能减弱因倾斜引起的模式畸变。     

钢带支撑轻量化椭圆镜的变形研究

应用有限元分析方法,借助于MSC.Nastran有限元分析软件,对钢带支撑下的大尺寸轻量化椭圆反射镜进行了受力、变形分析.用Excel绘出了钢带对椭圆镜边缘的正压力的分布曲线,得出了钢带对椭圆镜的正压力在最低点最大,随着支撑位置的上升而逐渐减小的分布规律.由镜面节点变形结果计算出椭圆镜在钢带支撑下的镜面面形误差RMS值为11.7nm,满足实际系统的面形准确度要求.     

Design of midwave infrared athermalization optical system with a large focal plane array

Based on the most advanced staring focal plane array which had a format of 640 × 480 and the pixel pitch of 15 μm, a set of all-sphere midwave infrared ahermalization optical system was designed. The working wavelength was in 3–5 μm, the full field of view was 8.58°, the relative aperture was 1/2, the efficient focal length (EFL) was 80 m. The opticalsystem consisted of four lenses with three kinds of material – Ge, ZnSe and Si. All surfaces were sphere, which was easier to process test, making the cost inexpensive, and it could avoid using diffractive surface and aspheric surface. The image quality of the system approaches the diffraction limit in the temperature range −60 °C-180 °C. The design results proved that, the high resolution midwave infrared optical system had compact structure, small volume, high resolution and excellent image quality, meeting the design requirements, so that it could be used for photoelectric detection and tracking system.     

On the reconstruction of the energy distribution of electrons accelerated in solar flares

A technique for reconstructing energy spectra of electrons accelerated in solar flares is suggested that is based on the rigorous solution of the inverse problem considering their X-ray bremsstrahlung. Model calculations are made for various spectra, and it is proved that this technique makes it possible to find the electron energy distribution in real flare events. The energy distribution of high-energy electrons accelerated in the solar flare observed on July 26, 2002, is reconstructed. It is shown that the hard X-ray spectrum of the flare may result from the bremsstrahlung of three groups of high-energy electrons.     

Flux and energy distribution of axial protons emitted from the hydrogen plasma focus

Experimental results and theoretical studies show that protons from the hydrogen plasma focus are emitted predominantly in the axial direction. In this work the results of the flux and energy distribution measurements of the axial protons using CR-39 detector are presented. The main purpose of the experiment is to test the suitability of a plasma focus device as a source for (p,) nuclear reactions, especially and .     

Full correction of spherical aberration for the lens with a spherical refractive index distribution

The potential to create a lens with a spherical gradient of refractive index, transforming a divergent entrance homocentric beam into a convergent output homocentric beam, is shown. The lens has the first and the second spherical surfaces. The second surface is isoindicial. The distribution law of the refraction index for the lens material, and the basic parameters of the lens are obtained in analytical form.     

Optimization of the input surface of a thick-lens spatial-integrator array for maximum flux transfer efficiency

The radius of curvature of the input surface of a thick lens spatial integrator array is a free parameter that can be customized for a maximum flux transfer efficiency. With this procedure each element is different but the spatial integration feature remains for the whole array. The calculation is based on a real ray-tracing evaluation that also takes into account the transmissivity of the diopters. The flux transfer on the synthetic image is doubled when the input surfaces are propoerly optimized.     

Reflectivity characteristics of the fiber loop mirror with a polarization controller

In this paper, reflectivity characteristics of a fiber loop mirror (FLM), which is formed by inserting a fiber polarization controller (PC) into the fiber loop of an ordinary FLM, are investigated in detail. A theoretical model for determining the reflectivity characteristics of the FLM is present by using the equivalent optical path technique, and the reflectivity characteristics of the FLM are then simulated with the model. The simulation results show that, when the FLM is based on a 3 dB optical coupler (OC), the reflectivity of the FLM may be continuously adjusted to any value between 1 and 0 by changing the PC state, i.e. by either changing the fast axis orientation or the birefringence intensity of the PC alone, as well as both of them; the reflectivity spectra of the FLM are wide and flattened for any PC state, mainly limited by the operating bandwidth of the OC used. The reflectivity characteristics of the FLM are further tested experimentally. The results verify that the reflectivity of the FLM may truly be continuously adjusted between its maximum and minimum values by changing the PC state. The obtainable maximum and minimum reflectivities of the FLM are measured to be 93% and 2%, respectively. Moreover, the experimental results are in agreement with those of the simulations.     

Comparison of different switching techniques in a cavity soliton laser

We compare three different switching techniques for the control of cavity solitons in a VCSEL-based cavity soliton laser, one incoherent and the other two semicoherent with different injection frequencies. We show that the switching dynamics and energies can be very different depending on the type of injection.     

Non-Hermitian systems of Euclidean Lie algebraic type with real energy spectra

We study several classes of non-Hermitian Hamiltonian systems, which can be expressed in terms of bilinear combinations of Euclidean–Lie algebraic generators. The classes are distinguished by different versions of antilinear (PT)-symmetries exhibiting various types of qualitative behaviour. On the basis of explicitly computed non-perturbative Dyson maps we construct metric operators, isospectral Hermitian counterparts for which we solve the corresponding time-independent Schrödinger equation for specific choices of the coupling constants. In these cases general analytical expressions for the solutions are obtained in the form of Mathieu functions, which we analyze numerically to obtain the corresponding energy spectra. We identify regions in the parameter space for which the corresponding spectra are entirely real and also domains where the PT symmetry is spontaneously broken and sometimes also regained at exceptional points. In some cases it is shown explicitly how the threshold region from real to complex spectra is characterized by the breakdown of the Dyson maps or the metric operator. We establish the explicit relationship to models currently under investigation in the context of beam dynamics in optical lattices.     

诺莫图法在薄透镜和球面镜成像分析中的应用

在满足近轴光线的条件下,可以利用成像公式和光路图法分析薄透镜或球面镜的物像关系,而本文介绍的这种诺莫图法,可以在直角坐标系上用坐标图示法分析薄透镜和球面镜的物像关系,不仅可以精确求得实物或虚物的成像位置,还可以判断出像的性质,具有简单、直观等特点,可以作为分析物像关系的一种补充手段.