Development Of Optical Fiber-Based Micro-Processing Technologies And Functional Devices

With the rapid development of optical fiber communication and fiber-optic sensor technologies, the optical fiber-based devices have been widely employed in many aspects of the human life. Recently the micro-fabrication technologies for the optical fiber devices have attracted great research interests both academically and industrially. This thesis mainly focuses on the study of fiber grating inscription technology for new types of optical fibers, chemical etching, functional micro-processing and optical lithography technologies for novel optical fiber devices, and their optical fiber sensing applications.Firstly, a brief overview of the research background of optical fiber micro-machining technologies is presented. Then the classification and theory of the optical fiber gratings and their fabrication technologies are introduced, and the fabrication system used in this thesis is presented. The fiber gratings inscription technology for the microstructure fiber and the lithography technology for fiber-end microtip have been experimentally demonstrated. Microstructure fiber Bragg gratings were fabricated by using the193nm Excimer laser and its spectral characteristics have been tested and compared with simulation analysis. Different fiber-end microtips with smooth surface have been fabricated on the optical fiber-end facet by the light-induced polymerization lithography. A6.85dB improvement in the excitation and coupling efficiency of the second-order optical mode has been experimentally achieved and used for microfluidic refractive index sensing applications. Experimental results revealed that the sensitivity of the second-order optical mode was around6.25times higher than that of the fundamental optical mode due to its relatively stronger evanescent wave.After that, the status and classification of the fiber-optic interferometers are introduced and a novel thin-core fiber modal interferometer was experimentally demonstrated. The sensitivity optimization was realized by the chemical etching technology and the refractive index sensitivity up to24584nm/R.I.U was illustrated in the optofluidic sensing experiments. Self-assembly of the probe DNA molecules was investigated and a label free DNA biosensor based on the cladding etched thin-core fiber modal interferometer was achieved. Subsequently the packing process was successfully employed to implement a microfluidic chip.Then, based on the theory of optical fiber gratings, the reflective long period grating sensor and low-loss microfiber Bragg grating sensors are proposed and experimental demonstrated by using chemical etching and metal coating technologies. A core mode scatter was formed in the optical fiber core region using the chemical etching method, and a fiber end-face mirror was fabricated through metal film coating technology. The reflective long period grating sensor with SNR of15dB at the central wavelength was demonstrated in the sensing applications. Meanwhile, a mechanically drawing aided HF etching method to fabricate a low-loss high-sensitivity microfiber Bragg grating sensor was presented. Through a precisely mechanically drawing of the optical fiber during HF etching process, a very smooth microfiber Bragg grating with a diameter of3.3um was obtained and a6.29dB improvement in reflection intensity was achieved.Finally, the fiber-end facet devices and some related fabrication technologies are described. The fiber-end facet devices have the advantages including compactness and flexible configuration. However, the current fabrication process has the drawback of high cost and low production. A scheme for the mass production of fiber-end facet with photonic crystal membrane based on the laser interference lithography was proposed and experimental demonstrated.