基于银纳米链的马赫-曾德干涉仪结构的生物传感器

Biosensor based on plasmonic Mach-Zehnder interferometer with metallic gratings

优化了一种基于表面等离激元银纳米链的马赫-曾德干涉式传感结构.该结构由参考臂、传感臂及纳米线波导构成.纳米线波导由银纳米线包裹一定厚度的硅来构成.引入两条银纳米链分别作为马赫-曾德干涉仪的参考臂和传感臂,并研究所设计结构的传输特性,通过降低传输损耗以提高所设计结构的精确度与灵敏度.相比于两条完全相同的银纳米线作为参考臂和传感臂的情况,在参考臂和传感臂改为银纳米链后,传输特性有明显提高,单位长度损耗明显降低.这是由于银纳米链中的单元结构之间的长程/库仑相互作用增强了结构中的电磁场,进而降低了传输损耗.将两条银纳米链的晶格常数设置为不同的情况,研究发现,在特定的银包硅纳米线的宽度与某些占空比下,含有非对称的银纳米链结构的单位传输损耗小于含有对称的银纳米链结构.由此可以知道,具有小损耗的银纳米颗粒链可以弥补大损耗的银纳米颗粒链的传输损失.利用这个特点,进一步优化设计结构,将一侧银纳米链改为纳米线.改变另一侧银纳米链的晶格常数与占空比,可以发现大多数情况下,这类结构传输特性优于含有两条银纳米链以及含有两条银纳米线的结构.本文的设计结构可以大幅减小传统的马赫-曾德干涉仪的传输损耗,且在结构的制备过程中容错率高,在实际应用中有巨大的潜在应用价值.

In this paper, a Mach-Zehnder interferometric sensing structure based on silver nanochains of surface plasmons is optimized. The structure consists of a reference arm, a sensing arm and a nanowire waveguide.Nanowire waveguides are composed of silicon nanowires wrapped with a certain thickness of silver. Introduce two silver nanochains as the reference arm and the sensing arm of the Mach-Zehnder interferometer. And research the transmission characteristics of the designed structure. Improve the accuracy and sensitivity of the designed structure by reducing the transmission loss. Compared with two identical silver nanowires as the reference arm and the sensing arm. After the reference arm and the sensing arm are changed to silver nanochains, the transmission characteristics are significantly improved, and the loss per unit length is obviously reduced. This is because the long-range or coulomb interaction between the unit structures of the silver nanochains enhances the electromagnetic field in the structure, thereby reducing the transmission loss. We set the lattice constants of the two silver nanochains to different situations. The study found that under the wider width of silicon-coated silver nanowires and certain duty ratios. The unit transmission loss of a structure containing asymmetric silver nanochains is smaller than that of a structure containing symmetric silver nanochains. It can be known that silver nanoparticle chains with small loss can compensate for the transmission loss of silver nanoparticle chains with large loss. Using this feature, we further optimized the design structure and changed one side of the silver nano-chain to nano-wire. Change the lattice constant and duty cycle of the silver nanochain on the other side. We have found that in most cases, this type of structure has better transmission characteristics than a structure containing two silver nanochains and a structure containing two silver nanowires. Our design structure can greatly reduce the transmission loss of the traditional Mach-Zehnder interferometer. Moreover, the fault tolerance rate is high in the preparation process of the structure. It has huge potential application value in practical application.