基于光纤光镊的长距离微粒可控操纵

在液体中灵活操纵微粒或细胞,特别是将细胞或微粒运输到指定位置,已经被证明在细胞分析、疾病诊断、药物递送等方面有着至关重要的作用。针对细胞或微粒非接触光学捕获的灵活性受限于光纤光镊操纵距离短的问题,提出了一种结构简单且具有长距离非接触可控操纵微粒的新型光纤光镊。利用加热和拉伸技术制作了类锥形平口光纤探针,980 nm的激光经过光纤探针后会对微粒产生大的散射力,将微粒逐渐推离光纤端口,同时借助反向流体阻力,在不移动光纤探针的情况下通过调节激光器光源的输出功率,对轴向位置上直径为6μm的聚苯乙烯微粒可以进行长达102.2μm的可控往返操纵,应用有限元法仿真了光镊的光场强度分布,并采用麦克斯韦应力张量法分析了光镊对微粒的作用力。实验和仿真结果表明,所提出的类锥形平口光镊是可行的。     

光纤传感微创手术探针末端三维力测量方法

手术探针末端的接触力反馈是保障手术安全性的重要因素之一。本文针对穿刺手术探针末端三维力测量的需求,研究了基于核极限学习机(KELM)神经网络的光纤传感微创手术探针末端三维力测量方法。首先,设计了可植入光纤传感器的手术探针结构,将4根光纤布拉格光栅(FBG)传感器植入探针中,其中3根FBG用于力测量,1根FBG用于温度补偿。接着通过分析探针应力和应变之间的关系,建立了基于FBG的探针三维力传感模型。同时为了消除温度变化对光纤传感器的交叉影响,研究了光纤传感温度补偿方法。最后,为了验证本文所研究测量方法的有效性,对植入光纤光栅的探针进行了温度标定,并分别在常温和变温环境下进行了三维力测量。实验结果表明：KELM网络测量结果在常温环境下X、Y、Z方向上平均测量误差为0.22%、0.99%、0.65%;在20℃～40℃的变温环境下,X、Y、Z方向上平均测量误差分别为1.32%、1.03%、2%,本文所研究的KELM神经网络末端三维力测量方法具有较小的测量误差,在手术机器人力反馈领域有广阔的应用前景。     

SNOM/SFM结合的近场光学探针

介绍了近年来近场光学探针技术的进展，特别是可与扫描力显徽镜结合的探针制备技术。     

细胞弹性光散射计算与检测方法的研究进展

研究细胞光散射特性、掌握细胞光检测技术是光学诊断和光学治疗疾病的重要基础。总结了研究细胞光散射的理论方法,阐述了每种方法的理论结果和表述光散射特性的方式。给出了光散射光谱在细胞检测中的应用技术,并说明了每种方法的实验检测结果及其优点与不足。     

宝钢1580工作辊热变形的数值模拟与实验研究

根据现场的复杂工况，将轧辊辊身分为辊颈、辊端、辊肩、轧制区和非轧制区，综合考虑分段冷却、支撑辊、摩擦热和变形热等因素的影响，建立符合实际的边界条件，并根据热平衡原理建立了工作辊温度场数学模型。在宝钢1580热轧机上进行实验，详细分析了热凸度的瞬态变化以及热凸度在每块带钢轧制前后的变化，对热凸度间断的原因进行了分析，模型计算值和实测值吻合较好，表明模型工程实用性较强，为轧辊热变形的在线预报和控制提供了一定的依据。     

面向光纤熔融拉伸的电磁力施加装置设计与实验

设计了相应的电磁力施加装置以实现对超细径光纤熔融拉伸力的精确控制。采用有限元法分析不同线圈参数下电磁线圈与永磁铁之间电磁力的大小,获得电磁力与线圈各参数间的数学关系式。以拉伸系统性能要求及线圈骨架的外形尺寸为限制条件建立约束方程及目标函数进行优化求解,得到最优参数。在依据优化参数制作电磁线圈的基础上设计了电磁力控制电路,通过调节线圈电流精确控制电磁力。最后,进行电磁力施加装置性能实验。实验结果表明:光纤拉伸力的范围达到26.073 mN;光纤拉伸力的分辨率达到7.473 μN,满足超细径光纤熔融拉伸对拉伸力范围及分辨率的要求。     

Evaluation of nano-optical probe from scanning near-field optical microscope images

We studied a nanometre-sized optical probe in a scanning near-field optical microscope. The probe profile is determined by using a knife-edge method and a modulated transfer function evaluation method which uses nanometre-sized line-and-space tungsten patterns (with spaces 1 μm to 50 nm apart) on SiO₂ substrates. The aluminium-covered, pipette-pulled fibre probe used here has two optical probes: one with a large diameter (350 nm) and the other with a small diameter (10 nm). The small-diameter probe has an optical intensity ≈63 times larger than that of the large-diameter probe, but the power is about 1/25 of that of the large probe.     

Design and optimization of tapered structure of near-field fibre probe based on finite-difference time-domain simulation

The finite-difference time-domain method was employed to simulate light propagation in tapered near-field fibre probes with small metal aperture. By conducting large-volume simulations, including tapered metal-cladding waveguide and connected optical fibre waveguide, we illustrated the coupling between these guiding modes as well as the electric field distribution in the vicinity of the aperture. The high collection efficiency of a double-tapered probe was reproduced and was ascribed to the shortening of the cut-off region and the efficient coupling to the guiding mode of the optical fibre. The dependence of the efficiency on the tapered structure parameters was also examined.     

Resolution enhancing using cantilevered tip-on-aperture silicon probe in scanning near-field optical microscopy

Scanning near-field optical microscopy (SNOM) achieves a resolution beyond the diffraction limit of conventional optical microscopy systems by utilizing subwavelength aperture probe scanning. A problem associated with SNOM is that the light throughput decreases markedly as the aperture diameter decreases. Apertureless scanning near-field optical microscopes obtain a much better resolution by concentrating the light field near the tip apex. However, a far-field illumination by a focused laser beam generates a large background scattering signal. Both disadvantages are overcome using the tip-on-aperture (TOA) approach, as presented in previous works. In this study, a finite difference time domain analysis of the degree of electromagnetic field enhancement is performed to verify the efficiency of TOA probes. For plasmon enhancement, silver is deposited on commercially available cantilevered SNOM tips with 20nm thicknesses. To form the aperture and TOA in the probes, electron beam-induced deposition and focused ion beam machining were applied at the end of the sharpened tip. The results show that cantilevered TOA probes were highly efficient for improvements of the resolution of optical and topological measurement of nanostructures.     

Spatial distribution and polarization dependence of the optical near-field in a silicon microfabricated probe

This paper reports on the spatial distribution and polarization behaviour of the optical near-field at the aperture of a Si micromachined probe. A sub-100 nm aperture at the apex of a SiO₂ tip on a Si cantilever was successfully fabricated by selective etching of the SiO₂ tip in a buffered-HF solution using a thin Cr film as a mask. The aperture, 10–100 nm in size, can be reproducibly fabricated by optimizing the etching time. The optical throughput of several apertures was measured. For a 100 nm aperture, a throughput of 1% was approved. The probe shows a very high optical throughput owing to the geometrical structure of the tip. The spatial distribution of the near-field light is measured and simulated using a finite difference-time domain method. The polarization behaviour of apertures with different shapes was analysed using a photon counting camera system.     

Imaging of optical disc using reflection-mode scattering-type scanning near-field optical microscopy

A phase-change optical disc was observed using a reflection-mode scattering-type scanning near-field optical microscope (RS-SNOM). In an a.c.-mode SNOM image, the 1.2 μm × 0.6 μm recording marks were successfully observed although the data were recorded on the groove. In contrast, no recording marks could be resolved in a d.c.-mode SNOM image. These results are in good agreement with those from a numerical simulation using the finite difference time domain method. The resolution was better than 100 nm with a.c.-mode SNOM operation and the results indicate that recording marks in phase-change optical media can be directly observed with the RS-SNOM.     

Current-sensing scanning near-field optical microscopy using a metal probe for nanometre-scale observation of electrochromic films

A novel technique for scanning near‐field optical microscopy capable of point‐contact current‐sensing was developed in order to investigate the nanometre‐scale optical and electrical properties of electrochromic materials. An apertureless bent‐metal probe was fabricated in order to detect optical and current signals at a local point on the electrochromic films. The near‐field optical properties could be observed using the local field enhancement effect generated at the edge of the metal probe under p‐polarized laser illumination. With regard to electrical properties, current signal could be detected with the metal probe connected to a high‐sensitive current amplifier. Using the current‐sensing scanning near‐field optical microscopy, the surface topography, optical and current images of coloured WO₃ thin films were observed simultaneously. Furthermore, nanometre‐scale electrochromic modification of local bleaching could be performed using the current‐sensing scanning near‐field optical microscopy. The current‐sensing scanning near‐field optical microscopy has potential use in various fields of nanometre‐scale optoelectronics.     

多信道异质结构光子晶体滤波器

利用二维正方晶格介质柱型光子晶体(PC),设计了一款由4个线性渐变型微腔和异质结构光子晶体反射器组成的多信道下路滤波器。利用平面波展开法(PWE)以及二维时域有限差分法(2D-FDTD)分析了该异质结构滤波器的工作机制,并进一步探究了微腔参考面与异质结界面之间距离对下路效率的影响。研究表明,滤波器中的异质结反射器可以实现接近100%的反射,从而大幅度地提高了三端口滤波器的滤波效率。设计的多信道滤波器各个通道都能有效地实现下路滤波功能,其信道间隔为10nm,滤波效率均在90%以上,透射谱半高宽均在0.54nm以下,实现了较高的品质因子特性。该滤波器尺寸只有15.15μm×13.91μm,且滤波效率很高,适于在波分复用系统中进行复用与解复用,在未来光路集成应用中具有良好的应用前景。     

Characterization and fabrication of fully metal-coated scanning near-field optical microscopy SiO2 tips

The fabrication of silicon cantilever‐based scanning near‐field optical microscope probes with fully aluminium‐coated quartz tips was optimized to increase production yield. Different cantilever designs for dynamic‐ and contact‐mode force feedback were implemented. Light transmission through the tips was investigated experimentally in terms of the metal coating and the tip cone‐angle. We found that transmittance varies with the skin depth of the metal coating and is inverse to the cone angle, meaning that slender tips showed higher transmission. Near‐field optical images of individual fluorescing molecules showed a resolution < 100 nm. Scanning electron microscopy images of tips before and after scanning near‐field optical microscope imaging, and transmission electron microscopy analysis of tips before and after illumination, together with measurements performed with a miniaturized thermocouple showed no evidence of mechanical defect or orifice formation by thermal effects.     

拉曼光纤探针的研究进展及应用

拉曼光纤探针是近来发展较快的一个领域。本文介绍了拉曼光纤探针的原理及研究进展,对其在工业、化学、生物等领域的应用做了总结,并对其应用前景做了预测。     

Imaging of various surface properties of fluorescently labelled phospholipid Langmuir–Blodgett films with a combined scanning probe microscope

We present results of phase separation of a single-component system of 1,2-dihexadecanoyl- sn -glycero-3-phospho-[ N -(4-nitrobenz)-2-oxa-1,3-diazolyl]ethanolamine in which a liquid-condensed (LC) phase co-exists with a liquid-expanded (LE) phase. Domain formation in the co-existence region was studied using a newly developed combined scanning near-field optical microscope–atomic force microscope (SNOM–AFM). We demonstrate for the first time that the topographic, friction, fluorescence and surface potential distributions for a phase-separated single-component Langmuir–Blodgett film between the LE and LC phases can be simultaneously observed using the SNOM–AFM with a thin-step etched optical fibre probe.