Design And Research Of Fiber-tip Integrated Micro-nano Device

In this dissertation,micro-nano structure devices based on fiber-tip are designed and studied.The design and fabrication process of the devices are introduced in detail and the performance of the devices is studied.The micro-nano structure devices based on fiber-tip are also called “lab on tip” devices,it can be divided into sensors and beam shapers according to their use.This paper first summarizes the characteristics and development of these two kinds of fiber-tip devices,analyzes the realization process of device function,and then introduced the theoretical principles and optical phenomenon involved in the device.The influence of the intrinsic properties of the material on the device performance is discussed for the design and optimization of the device.A LSPR fiber sensor with nanohole array structure and a metasurface lens with adjustable focal length are designed respectively on the multimode fiber-tip.The LSPR fiber sensor based on nanohole array structure of gold film can achieve the unmarked sensing by excite the EOT phenomenon between gold and air hole,which makes the transmission of the structure sensitive to the refractive index of the surrounding medium.In this paper,the fabrication of nanohole arrays on gold film and the transfer process to the fiber-tip are pointed out.Then the transmission spectrum of the sensor is analyzed and the sensing characteristics of the sensor are studied.The all-dielectric metasurface lens is mainly based on the modulation of phase profile of the light wave,by satisfying the specific phase distribution needed for focusing,the focusing spot nearing the diffraction limit can be achieved.The structure of the lens is designed according to the core size of multimode fiber.By numerical analysis,the phase delay of 2? range is realized after optimizing the geometric parameters such as the height,width and duty ratio of the resonant unit.The focal length and focusing performance are studied through FDTD simulation software.Then the adjustable focal length of the designed lens was studied by using the thermo-optical effect of amorphous silicon material,and it is proved that the designed lens maintains good focusing performance under a large scale of focal length.