微纳金属光学结构制备技术及应用

微纳光学结构制备技术一直是微纳光子学器件发展的技术瓶颈.针对微纳光学结构制备技术向小尺寸、高精度和广泛应用发展的趋势,报道了基于电子束、X射线和接近式光学的混合光刻制作微纳金属光学结构技术.针对微纳光子学器件复杂图形开发了微光刻数据处理体系,基于矢量扫描电子束光刻设备在自支撑薄膜上进行1×高分辨率图形形成,利用X射线光...     

基于PDMS的光纤端面微纳结构转移法

微纳光纤传感器将微纳加工与光纤传感技术有机结合，具有重大的科研意义和产业化潜力。现有加工方法无法达到任意复杂三维结构可制备化，从而限制了微纳光纤传感器的发展。介绍了一种新型微纳加工方法，该方法在聚二甲基硅氧烷（PDMS）薄膜上实现微纳结构的制备，之后将薄膜连同微纳结构一同转移到光纤端面，在光纤端面实现人为定义三维立体微纳结构。通过在扫描电镜下对制备的样品进行检测，确认PDMS薄膜及其上三维结构可被无损转移至光纤端面。该方法具有易制备、低成本且可加工三维微纳结构的特点。     

面向柔性光电子器件的微纳光制造关键技术与应用

柔性光电子器件对微纳制造技术提出了更高、更多维度的要求,包括大幅面、表面复杂结构、跨尺度、透明或柔性基底等。主要介绍基于相位元件调制的3D激光直写技术和紫外连续变频光刻技术,它们可分别实现复杂表面浮雕结构和像素化纳米结构的精确制备。此外微纳结构限定性生长或涂布方法提供了一种绿色环保的材料功能化手段。借助微纳结构图形化、功能化平台,最后介绍了新型柔性光电子材料/器件的应用创新。可以预见,微纳光制造技术将推动柔性光电子产业的持续创新发展。     

激光全息光刻技术在微纳光子结构制备中的应用进展

微纳光子结构研究随着光子学、半导体物理学及微加工技术的发展而逐渐蓬勃开展,并在其结构、理论、制备技术等方面取得了系列进展。受限于目前的微加工技术水平,要成功制备大尺度、高质量的光子材料仍然存在着一定挑战。激光全息光刻技术作为一种简便快捷的微结构制作技术已经发展成为一种经济快速制作大面积微纳超材料及光子晶体模板的重要手段。介绍了激光全息光刻技术的原理,详细阐述了该技术在制作三维面心立方、木堆积结构、金刚石结构光子晶体以及光学周期类准晶、手性超材料、周期性缺陷结构等微纳光子结构中的应用研究进展。激光全息光刻技术成功制作微纳光子结构为光子材料在更多领域的广泛应用提供了基础和方法。     

基于三模冗余设计的低成本高可信微纳通用计算机

引入商用现货技术成为微纳卫星设计的发展趋势。针对微纳卫星电子系统低成本、小型化、高可靠的应用发展需求,分析对比国内外微纳卫星星载计算机设计特点,提出一种基于三模冗余设计的低成本、高可信微纳通用计算机体系架构,利用接口标准化、软件分层化设计和三模冗余、硬件看门狗等加固设计,构建了一套通用、稳定、可靠的电子系统,并展望了其在科学实验与新技术演示验证、分布式空间系统、军事等方面良好的应用前景。     

微纳卫星COTS器件应用研究

大量采用宇航级元器件进行航天器研制的模式,由于其“成本高、研制周期长、元器件性能不足”等缺点,已经难以满足微纳卫星“周期短、成本低、集成度高”的要求。因此提出了在微纳卫星上使用COTS(Commercial off-the-shelf)器件的方法;针对微纳卫星的特点,首先分析了微纳卫星对COTS器件的需要和风险,提出了COTS器件微纳卫星应用的选用原则、选用依据;在此基础上经过分析,提出了COTS元器件微纳卫星应用流程,有针对性提出了COTS器件应用的器件级和板级筛选方法,并开展了COTS器件的微纳卫星抗单粒子效应加固设计,进一步提高COTS器件应用的可靠性。通过在轨应用验证,结果表明,通过该方法选用筛选的COTS器件,在进行有效加固后可以满足微纳卫星在轨稳定运行的要求,同时为微纳卫星降低成本缩短研制周期提供了保障。该方法对COTS器件在微纳卫星中的应用提供了一般性指导意义。     

微纳光纤直径精细控制技术

为实时监测高通量激光系统中洁净情况,提出了基于微纳光纤的微量污染物传感技术。为消除微纳光纤外形结构误差对测试结果影响,首先理论研究了微纳光纤拉制过程,得到了加热长度和拉伸长度误差和引入微纳光纤外形结构偏差的关系,接着通过理论仿真得到了不同拉制参数条件下,微纳光纤外形结构误差情况,并得到了拉制长度为10 mm、直径为1.5 μm的最优制备参数,最后通过实测微纳光纤外形结构验证了理论仿真结果。实验结果表明,通过优化微纳光纤拉制参数可实现其外形结构的精细控制,为微纳光纤用于微量污染物传感工程实用化奠定基础。     

飞秒激光直写偏振转换器件和几何相位器件(特邀)

光学器件的微型化和集成化是当前研究的热点,其中利用微纳结构实现局域电磁改性的超构光学更是引人关注。本文从微纳结构的制备出发,总结了利用超衍射精密加工的飞秒激光直写技术,制备偏振转换器件和几何相位器件的工作。介绍了微纳结构改性的物理机制,飞秒激光直写光刻胶、飞秒激光烧蚀金属薄膜、飞秒激光诱导纳米光栅等手段在偏振转换器件和几何相位器件制备方面的进展,展望了飞秒激光微纳加工技术在超构光学器件制备方面的挑战。     

微纳光纤及其锁模激光应用

微纳光纤是一种直径接近或小于传输光波长的纤维波导,由于纤芯和包层折射率差较大,具有强光场约束、强倏逝场、低损耗、反常波导色散、表面均匀性好和机械性能高等特性。近年来,以纳米材料作为饱和吸收体的被动锁模激光器成为超短脉冲激光技术方向的研究热点。得益于微纳光纤的强光场约束能力及大比例倏逝场,纳米材料与微纳光纤的复合结构能显著增强光与物质的相互作用,进而降低该复合结构的饱和吸收阈值,为超短脉冲产生和非线性动力学等研究提供一个新颖而灵活的平台。同时,微纳光纤因具有反常波导色散、光谱滤波、饱和吸收和偏振敏感等特性,在激光器的色散调控、偏振锁模等方面获得应用。介绍了微纳光纤的制备和特性以及在锁模激光方面的典型应用和相关技术的最新进展,并就未来的发展方向进行了展望。     

聚焦激光束：从科研到教学的应用

列举了聚焦激光束在光镊、显微激光改性和显微测量等科研领域中的典型应用实例,设计了荧光检测以及激光微纳加工系统一体化的教学实验.通过显微光谱检测系统获得了红宝石的光致发光信号,并分析了光谱的产生机理.教师通过指导学生搭建聚焦激光光路,实现微纳加工和热光学性质测试,强化了学生在激光应用技术方面的知识与技能.     

Current status on the contribution of silica fibres to stellar interferometry

This paper reports on guided and integrated optics set-ups developed in our laboratory in the framework of aperture synthesis for astronomy. After summarising the function required to design a stellar interferometer, we propose guided components for these purposes. The implementation of these components is illustrated by two examples of interferometers with a view to using guided components as often as possible and testing an end-to-end imaging demonstrator.     

Decomposition of acoustic fields in quantised Bessel beams

Bessel beams are non-diffracting solutions to the wave equation, which become limited diffraction beams when implemented on finite apertures. In previous work we have applied Fourier-Bessel theory to deduce theoretically that the quantization of the Bessel beam profile on annular arrays results in a field which is a sum of limited diffraction fields. Here we demonstrate this for a five-ring, 20-mm diameter, 2.5-MHz transducer. The quantized field comprises a weighted sum of a main component corresponding to the desired field, along with three other major components and 28 lesser components representing undesired field components. The three major components correspond to limited diffraction beams with narrower beamwidths and shorter depths of field than the desired beam, and we show that these account for most of the discrepancies between the desired field and actual quantized field. An estimate and an interpretation of the number of field components as a function of the wavenumber are also given.     

Frequency-domain method based on the singular value decomposition for frequency-selective NMR spectroscopy

In several applications of NMR spectroscopy the user is interested only in the components lying in a small frequency band of the spectrum. A frequency selective analysis deals precisely with this kind of NMR spectroscopy: parameter estimation of only those spectroscopic components that lie in a preselected frequency band of the NMR data spectrum, with as little interference as possible from the out-of-band components and in a computationally efficient way. In this paper we introduce a frequency-domain singular value decomposition (SVD)-based method for frequency selective spectroscopy that is computationally simple, statistically accurate, and which has a firm theoretical basis. To illustrate the good performance of the proposed method we present a number of numerical examples for both simulated and in vitro NMR data.     

Summarizing Finite Mixture Model with Overlapping Quantification

Finite mixture models are widely used for modeling and clustering data. When they are used for clustering, they are often interpreted by regarding each component as one cluster. However, this assumption may be invalid when the components overlap. It leads to the issue of analyzing such overlaps to correctly understand the models. The primary purpose of this paper is to establish a theoretical framework for interpreting the overlapping mixture models by estimating how they overlap, using measures of information such as entropy and mutual information. This is achieved by merging components to regard multiple components as one cluster and summarizing the merging results. First, we propose three conditions that any merging criterion should satisfy. Then, we investigate whether several existing merging criteria satisfy the conditions and modify them to fulfill more conditions. Second, we propose a novel concept named clustering summarization to evaluate the merging results. In it, we can quantify how overlapped and biased the clusters are, using mutual information-based criteria. Using artificial and real datasets, we empirically demonstrate that our methods of modifying criteria and summarizing results are effective for understanding the cluster structures. We therefore give a new view of interpretability/explainability for model-based clustering.     

Equal-time kinetic equations in a rotational field

We investigate quantum kinetic theory for a massive fermion system under a rotational field. From the Dirac equation in rotating frame we derive the complete set of kinetic equations for the spin components of the 8- and 7-dimensional Wigner functions. While the particles are no longer on a mass shell in the general case due to the rotation–spin coupling, there are always only two independent components, which can be taken as the number and spin densities. With help from the off-shell constraint we obtain the closed transport equations for the two independent components in the classical limit and at the quantum level. The classical rotation–orbital coupling controls the dynamical evolution of the number density, but the quantum rotation–spin coupling explicitly changes the spin density.     

Review of fluorescence anisotropy decay analysis by frequency-domain fluorescence spectroscopy

This didactic paper summarizes the mathematical expressions needed for analysis of fluorescence anisotropy decays from polarized frequency-domain fluorescence data. The observed values are the phase angle difference between the polarized components of the emission and the modulated anisotropy, which is the ratio of the polarized and amplitude-modulated components of the emission. This procedure requires a separate measurement of the intensity decay of the total emission. The expressions are suitable for any number of exponential components in both the intensity decay and the anisotropy decay. The formalism is generalized for global analysis of anisotropy decays measured at different excitation wavelengths and for different intensity decay times as the result of quenching. Additionally, we describe the expressions required for associated anisotropy decays, that is, anisotropy decays where each correlation time is associated with a decay time present in the anisotropy decay. And finally, we present expressions appropriate for distributions of correlation times. This article should serve as a reference for researchers using frequency-domain fluorometry.     

Higher order effects in the master equation for coupled systems

The usual derivations of the master equation for coupled systems such as the laser make an assumption of weak coupling both for the coupling of the components to their heat baths and for the internal coupling between the components. It is this second condition that we wish to relax. In the usual derivation of the irreversible part of the master equation the approximation is made that the density operator for the coupled system factorizes into a product of the density operators for the two components. However when strong coupling is present, such as in high intensity lasers this approximation is no longer valid. To illustrate how the irreversible part of the master equation may be derived without making the factorization ansatz we consider the case of two coupled boson fields. Our derivation leads to additional terms in the usual master equation arising from correlations between the heat baths introduced by the coupling. This modified master equation yields the correct stationary solution for the density operator of the coupled system, whereas the usual master equation leads to a stationary solution for the density operator correct for the free components only.     

Fast Estimation of Scatter Components Using the Ordered Subset Expectation Maximization Algorithm for Scatter Compensation

In this work we propose a method for scatter compensation in single photon emission computed tomography imaging, by which we can estimate the scatter components in projections in high speed with good accuracy. The method is that we first estimate the scatter components in projections based on scatter response kernels by one time of ordered subsets expectation maximization iterative reconstruction, and then subtract the estimated scatter components from the projections and complete reconstruction by filtered back-projection method. The principle is that the image corresponding to the scatter components in projections consists largely of low-frequency components of an activity distribution; these low-frequency components will converge faster than the high ones in iterative reconstruction. Therefore, we can estimate the low-frequency component image before the image converges with the high-frequency ones, and obtain the scatter components by re-projecting the low-frequency component image with scatter response kernels. The effects of the proposed method were compared with the dual- and triple-energy window methods using experimental measurements. The results show that good accuracy in estimated scatter components, good uniformity of scatter compensation at the center and the side of an object, and good noise property can be acquired by this method.     

Analytical evaluation of the Fourier components of wavelength-modulated Gaussian functions

Modulation techniques are often used in experiments where noise levels are significant, enabling weak signals to be detected. Gaussian lineshapes can be present in situations such as with tunable diode laser absorption spectroscopy of low-pressure gases, requiring the evaluation of the Fourier components of Gaussian lineshapes. These Fourier components have been evaluated only numerically in the past. In the present research, we derive exact analytical expressions for the Fourier components of a modulated Gaussian signal. We also evaluate the dimensionless modulation amplitudes that maximize the even and odd harmonics.     

Analysis of optical characteristics of holey photonic crystal devices with the extended coupled-mode formalism

Presented here is a new approach for analysis of the so-called holey photonic crystals—a class of electro-optical components, in which periodicity of air holes in dielectric media is used for confinement of light. This class includes several kinds of microstructured fibers, semiconductor lasers etc. Accurate evaluation of optical characteristics of those devices is usually a complicated problem due to the large dimensions and the fine structure of their refractive index distribution. Furthermore, usually, only numerical solutions for this class of optical components are available. The overwhelming majority of the physical models, suitable for analysis of holey photonic devices, proceed from the “natural” assumption: the devices are considered as arrays of air holes, surrounded by dielectric material. In this work we propose another model. Namely, we treat them as arrays of dielectric spots (waveguides), embedded in the air (cladding material). This model allows utilization of the extended coupled-mode theory (a relatively new approach designed for analysis of infinite arrays of coupled waveguides and previously considered inapplicable to holey optical components) for calculations of the latter. In this sense, we present a new method for analysis of holey photonic crystals. On the one hand, our method allows analytical evaluation of some optical characteristics of holey optical components (such as the number of photonic bands and bandwidth). On the other hand, accurate numerical computation of the photonic band structure of the holey photonic devices, incorporating a large number of holes, can be done with this technique on a timescale of several minutes.