Plasmonics and Near-Field Optics: Towards the limits of electromagnetic energy confinement

等离激元和近场光学：迈向电磁能限制的极限

• 批准号: EP/C522834/2
• 负责人: Stefan Maier
• 金额: --
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2007
• 资助国家: 英国
• 起止时间: 2007 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FC522834%2F2
• 关键词: Plasmonics; Near; Field; Optics; Towards

The size of electronic devices has decreased at an amazing speed during the last decades, and this has made possible the fabrication of highly integrated microelectronic chips, which have revolutionized our daily life and are found everywhere from fast personal computers to complex electronics in modern automobiles. While dimensions of transistors are fastly approaching typical sizes on the order of 10 nanometres (the millionth part of a millimetre), the integration of optical devices such as light guides and cavities for light storage has lagged behind, so that there exists a size gap of about a factor 10-100 between state-of-the-art electronic and optical devices. In order to create ultrafast computers that transmit information between and on chips via light, or to optically investigate single molecules, this size gap must be closed. For this vision to come true, a fundamental barrier that limits the creation of ultrasmall light beams has to be broken - the so-called diffraction limit , which states that light cannot be confined to dimensions smaller than about half the wavelength in the material of interest. There is a way around this obstacle, however, via the creation of lower dimensional light confined to the interface between a metal and a dielectric, so called surface plasmon-polaritons. These excitations are created via the coupling of light to the motion of the conduction electrons at a metallic interface, and it has been shown recently that light can be confined this way to dimensions below the diffraction limit of light. This has enabled the creation of a number of plasmonic devices such as waveguides and nanoparticle resonators. Here we propose to work on some of the major challenges currently encountered in this field, namely the efficient interfacing of such tiny optical devices with conventional optical light guides such as fibres, and the investigation of the inherent trade-off between high localization and (heating) loss in plasmonic structures. As a main research tool, we will use a scanning near-field optical microscope (SNOM), which locally illuminates or collects light from nanoscale structures via a tip with a very small hole (about 100 nanometre diameter) in it. The resolution of such a microscope is not limited by the diffraction limit, but by the hole size alone. However, the shape of the light emerging from such an aperture is not defined very well, and the throughput is generally low, making the controlled investigation of plasmon waveguides or resonators difficult. We will overcome this obstacle by using thinned optical fibres named tapers , which can leak out light in a controlled way, as near-field probes. This will allow us to develop ways to carry out white-light spectroscopy of metallic nanostructures such as single particles of complex shapes, waveguides and resonators using this principle, working towards highly efficient interfaces between conventional optical and nanoscale metallic light guides. The outcome of these efforts will affect both the further establishment of near-field optics a routine laboratory technique, and the design of a plasmon optics infrastructure. In this regard, novel geometries for the guiding and confinement of light such as small gaps between metallic surfaces or concentric rings will be investigated with this technique and by using powerful computer simulations. These studies will work towards the integration of low-loss waveguides with high confinement light storage cavities, which is important for the creation of all-optical biological sensors and switches.

在过去的几十年里，电子设备的尺寸以惊人的速度缩小，这使得制造高度集成的微电子芯片成为可能，这些芯片彻底改变了我们的日常生活，从快速的个人电脑到现代汽车上复杂的电子设备无处不在。虽然晶体管的尺寸正在迅速接近10纳米（毫米的百万分之一）的典型尺寸，但光学器件（如光导和光存储腔）的集成却落后了，因此在最先进的电子和光学器件之间存在大约10-100倍的尺寸差距。为了制造出通过光在芯片之间和芯片上传输信息的超快计算机，或者对单个分子进行光学研究，这个尺寸差距必须缩小。为了实现这一愿景，必须打破一个限制超小型光束产生的基本障碍——所谓的衍射极限，即光不能被限制在小于所研究材料波长一半的尺寸内。然而，有一种方法可以绕过这个障碍，那就是在金属和电介质之间的界面上产生低维光，即所谓的表面等离子体极化子。这些激发是通过光与金属界面上传导电子运动的耦合产生的，最近已经表明，光可以以这种方式限制在光的衍射极限以下的尺寸上。这使得许多等离子体器件，如波导和纳米粒子谐振器的产生成为可能。在这里，我们建议研究目前在该领域遇到的一些主要挑战，即这种微型光学器件与传统光学光导（如光纤）的有效接口，以及对等离子体结构中高局域化和（加热）损失之间固有权衡的研究。作为主要的研究工具，我们将使用扫描近场光学显微镜（SNOM），它通过一个带有非常小的孔（直径约100纳米）的尖端局部照亮或收集来自纳米级结构的光。这种显微镜的分辨率不受衍射极限的限制，而只受孔大小的限制。然而，从这样一个孔径出来的光的形状并没有很好地定义，而且吞吐量通常很低，这使得对等离子体波导或谐振器的控制研究变得困难。我们将通过使用一种名为“锥”的细光纤来克服这一障碍，这种光纤可以作为近场探测器，以一种可控的方式泄漏光。这将使我们能够利用这一原理开发出对金属纳米结构（如复杂形状的单粒子、波导和谐振器）进行白光光谱分析的方法，努力实现传统光学和纳米级金属光导之间的高效界面。这些工作的结果将影响近场光学的进一步建立和等离子体光学基础设施的设计。在这方面，用于引导和限制光的新几何形状，如金属表面或同心圆之间的小间隙，将用这种技术和使用强大的计算机模拟来研究。这些研究将致力于低损耗波导与高约束光存储腔的集成，这对于创建全光生物传感器和开关非常重要。

项目成果

Nanoplasmonics: Engineering and observation of localized plasmon modes

• DOI: 10.1002/lpor.201100027
• 发表时间: 2012-05
• 期刊: Laser & Photonics Reviews
• 影响因子: 11
• 作者: Y. Sonnefraud;A. Koh;D. McComb;S. Maier

Internal excitation and superfocusing of surface plasmon polaritons on a silver-coated optical fiber tip

• DOI: 10.1103/physreva.75.063822
• 发表时间: 2007-06-01
• 期刊: PHYSICAL REVIEW A
• 影响因子: 2.9
• 作者: Ding, W.;Andrews, S. R.;Maier, S. A.
• 通讯作者: Maier, S. A.