Grating and waveguide plasmonic sensors

飞秒激光器产生的光脉冲非常短，同时非常强大。当来自这种激光器的光向下聚焦时，可用的强度能够改变透明材料的结构，甚至从表面烧蚀材料。我们已经开发了飞秒激光脉冲与光学玻璃的相互作用的理解，以便根据脉冲参数，我们可以创建光波导，耦合器，弯曲和光栅结构，甚至加工表面，以改变其在微米尺度上的拓扑结构。在这个项目中，我们希望将这些能力结合起来，创造一个通用的等离子体传感技术。表面等离子体激元是薄金属膜中自由电子的振荡，并且这些可以使用来自在靠近金属膜的波导中行进的光的能量来产生。重要的是，从光到等离子体的能量转移仅发生在明确定义的波长处，该波长强烈取决于金属膜上方等离子体的电场延伸的微米厚区域中的折射率。通过在金属薄膜附近的波导中发送宽光谱的光，并注意哪种波长被器件吸收，就可以非常精确地测量金属上方的折射率。如果金属薄膜上涂有化学或生物化学特定涂层，那么传感器就可以检测到特定的物种。在本提案中，我们计划研究适体在这方面的用途。核酸适体是一种寡核苷酸序列，它可以被设计成与特定的分子、蛋白质、DNA序列甚至细胞结合，提供了一种高度灵活的传感技术。该技术的另一个应用是作为监测细胞运动和生长的手段。细胞在特定点处接触表面，并且如果细胞被放置在等离子体支持金属膜上，则光将在接触点处从等离子体场散射。这种光可以使用显微镜观察，这将允许随着时间的推移跟踪细胞的运动。细胞根据表面拓扑结构做出不同的反应，飞秒激光可用于修改传感器表面，以研究不同表面拓扑结构对细胞运动和生长的影响。

Femtosecond lasers produce pulses of light which are extremely short and at the same time extremely powerful. The intensities available when light from such a laser is focussed down are capable of modifying the structure of transparent materials or even ablating material from the surface. We have developed an understanding of the interaction of fs laser pulses with optical glasses so that, depending on the pulse parameters, we can create light waveguides, couplers, bends and grating structures or even machine the surface to alter its topology on a micron scale.In this project we wish to bring these capabilities together to create a generic plasmonic sensing technology. Surface plasmons are oscillations of the free electrons in a thin metal film and these can be generated using the energy from light travelling in a waveguide close to the metal film. Importantly, the transfer of energy from the light to the plasmon only occurs at a well defined wavelength which depends strongly on the refractive index in a micron thick region above the metal film where the electric field of the plasmon extends. By sending a broad spectrum of light though the waveguide near the metal film and noting which wavelength is absorbed by the device it is possible to measure the refractive index above the metal very accurately.If chemical or biochemical specific coatings are applied to the metal film then the sensor can detect specific species. In this proposal we plan to investigate the use of aptamers in this regard. Aptamers are oligonucleotide sequences, which can be designed to bind to specific molecules, proteins, DNA sequences or even cells, providing a highly flexible sensing technology.An additional application for the technology is as a means of monitoring cell movement and growth. Cells contact a surface at specific points and if a cell is placed on the plasmon supporting metal film, light will be scattered from the plasmon field at the points of contact. This light may be viewed using a microscope which will allow the movement of the cells to be tracked over time. Cells respond differently depending on surface topology and the fs laser can be used to modify the sensor surface to enable studies of the effect of different surface topologies on cell movement and growth.