Low-loss light propagation in the chain of microcavities

According to the focusing property of the photonic nanojet, the coupling characteristics for the chain of microcavities have been studied. Low-loss light propagation in the chain of microcavities is proposed. The influence of different wavelengths on the intensity of the photonic nanojet and the location of the focal spot are given. Intensity distribution and transmission characteristics for the chain of coupled spherical microcavities are analysed. Simulation results and theoretical analysis show that the chain of spherical microcavities has a highly focused beam and low-loss characteristics because of the focusing effect and backscattering enhancement of the photonic nanojet. A low-loss waveguide can be designed by using these properties of the chain of spherical microcavities. Sub-wavelength focusing of the beam, high optical throughput, and broad spectral transmission properties make the chains of microspheres able to be used in a variety of biomedical applications including minimally invasive and ultraprecise laser surgery.     

Three-dimensional molecular dynamics study of aperture shape effect on nanojet ejection

Three-dimensional molecular dynamics (MD) simulations of nanojet ejection with different aperture shapes are reported. The simulations use the Lennard-Jones 12-6 (LJ) potential to describe the intermolecular interaction. Using non-equilibrium MD, argon nanojet ejection is simulated under vacuum conditions. According to the analysis, different aperture shapes influence the ejection processes. The ejection speeds were 23.7 and 63.2?m/s respectively in the simulation. The speed of spurting atoms in type A nanojet was slower than the other types and it became more obvious when the process time increased. The variations in velocity, density, pressure, and temperature were found with the aid of MD. The liquid temperatures were set at 50, 100, 150, and 200?K, respectively, to examine nanojet break-up characteristics. The liquid temperature inside the nanojet was found to be a factor that induce break-up. A higher temperature led to faster nanojet break-up.     

扫描探针加工技术的新进展及扫描等离子体加工技术的研究

扫描探针加工技术作为一种无掩模微细加工手段以其所需设备简单和加工精度高达纳米量级等优点 ,近年来受到广泛的重视和研究。但目前扫描探针加工技术存在加工效率低、可重复性差、可加工材料非常有限等缺点。采用探针阵列并结合其他加工技术的并行工艺 ,可以提高加工效率 ,拓展应用范围。本文以纳米喷流加工和蘸水笔纳米加工为例介绍了扫描探针加工技术这一方面的最新进展 ,阐述了它们各自的基本原理和特点。最后 ,提出了一种基于并行探针驱动的扫描等离子体加工技术 ,结合了扫描探针加工精度高和等离子体加工适用材料广泛的优点 ,为小批量多品种微系统和纳米器件的加工探索出一种新方法。     

Tunable photonic nanojet achieved using a core–shell microcylinder with nematic liquid crystal

A tunable photonic nanojet achieved using a core–shell microcylinder with nematic liquid crystal is reported. The core–shell microcylinder can be obtained by the infiltration of liquid crystal into the air core of a microcylinder. The refractive indices of the liquid crystals can be changed by rotating the directors of the liquid crystals. Therefore, we were able to control the flow direction of the photonic nanojet in two-dimensional core–shell microcylinder structures. Using high resolution finite-difference time-domain simulation, we demonstrate that the photonic nanojet can be continuously tuned in the core–shell microcylinder. The horizontal and vertical shifts of photonic nanojet depend strongly on the director of the liquid crystals. Such a mechanism of nanojet adjustment should open up a new application for using visible light to detect nanoparticles, optical gratings, and single molecules with subwavelength spatial resolution.     

新型光子纳米射流器件的设计

光子纳米射流是一种高强度,极窄的亚波长电磁场区域,它是由介电微球或微柱体的Mie散射对电磁场的聚焦作用产生的。光子纳米射流广泛应用于激光加工、纳米光刻、光学高密度存储以及超分辨率显微镜。从径向偏振光的角度出发,使用一种介电圆环结构对光束进行聚焦,由于径向偏振光在焦点区域可以产生较强的纵向场,通过优化圆环的尺寸、折射率以及与物镜焦点的相对位置,可以得到超过90%光束质量的纵向光子纳米射流,而且强度相比于未使用圆环时可以提高约一个数量级,并在高折射率下可以获得半高全宽小于衍射极限尺寸的光斑,因此该结构预计可以在粒子加速、光镊以及拉曼光谱学中有所应用。     

光子纳米喷流的性能及应用

光子纳米喷流是光照射直径与波长相当或略大于波长的无损电介质微颗粒时,会在微颗粒后表面一定距离处形成高强度、紧聚焦光束。光子纳米喷流具有大于照射光的强度、最小的半高宽值能够小于衍射极限的光束宽度、传播超出倏势场区域和较强的背向散射等优异特性,在光信号增强、微纳加工与制造、超分辨光学成像、超灵敏捕获和探测等领域具有重要应用。该文首先介绍了光子纳米喷流的源头和发现;其次,对光子纳米喷流的模型、理论、形貌特征、实验测量和主要特性进行了阐述;再次,调研和讨论了光子纳米喷流的几个重要应用;最后,对光子纳米喷流进行了总结和展望。     

Controlling the electric field enhancement factor of photonic nanojets by using the magneto-optical effect

In recent years, many researchers have studied photonic nanojets. These nanojets are created when an incident plane wave is focused into a narrow and high intensity emerging optical beam leaving a micro-object (e.g. microcylinder). These narrow beams may find applications in particle imaging and detection, optical sensors, enhanced Raman scattering, and particle manipulation. They also allow the projection of a particle to the far-field where it can be easily visualized. In this paper, it is shown that the electric field enhancement factor can be dynamically controlled by the application of an external intense magnetic flux density.