All-in-fiber sensing and light generation based on specialty fibers

• Main Author: Zhang, Nan
• Other Authors: Wei Lei
• Format: Theses and Dissertations
• Language: English
• Published: 2018
• Subjects: DRNTU::Engineering::Electrical and electronic engineering
• Online Access: http://hdl.handle.net/10356/74200
• Institution: Nanyang Technological University

All-in-fiber sensing and light generation devices are facing increasing demand due to their distinct features of being free-standing and robust, great compactness, easy handling, low waveguide losses and low cost for mass production. Compared with conventional fibers, specialty fibers are able to provide better sensing and light generation performance since they offer great flexibility in manipulating light guidance property through simply tuning fiber cladding structure, and enhanced light-matter interaction by hosting aqueous matter in the air channels running along the entire fiber length. Currently, the development and applications of high-performance all-in-fiber sensing and light generation devices are still hindered by low sensing sensitivity, difficulties in the replacement or manipulation of liquids in the fiber cladding channels, and the small surface area of light emission from the fiber cross-section. To address the challenges and limitations mentioned above, some all-in-fiber solutions for sensing and light generation are systematically investigated in this thesis. First, a side-channel photonic crystal fiber (SC-PCF) is designed, fabricated and manipulated for developing highly sensitive aqueous sensing platforms with in-line liquid circulation capabilities. The SC-PCF has a solid core and a triangular lattice cladding structure, while partial lattice cladding is intentionally removed to enable efficient liquid flow in the fiber channels and strong light-matter interaction. By precisely splicing this SC-PCF to side-polished single mode fibers (SMFs), a fiber long period grating (LPG) and a Sagnac interferometer are experimentally demonstrated to enable all-in-fiber optofluidic refractive index (RI) sensing and biological sensing, respectively. A high RI sensitivity of 1145 nm/RIU is achieved with the SC-PCF LPG, and a low limit of detection (LOD) of 1 ng/mL cardiac troponin T (CTT) protein is obtained with the highly sensitive Sagnac interferometer. To further improve the LOD, an ultrasensitive surface enhanced Raman sensing (SERS) platform is proposed and demonstrated with an optimized geometry of the SC-PCF, and an ultra-low LOD of 50 fM Rhodamine 6G (R6G) solution is achieved. Last, an all-in-fiber light generation is demonstrated based on a multilayer photonic bandgap (PBG) fiber laser with quantum dots (QDs) solution as the gain medium infiltrated in the hollow core. The PBG fiber laser platform has unique characteristics of large emission surface perpendicular to the fiber axis and remote pumping configuration, which provides a substantial impact on both studies of lasing mechanism and future developments of a variety of applications ranging from omnidirectional displays to light sources for biomedical analysis and phototherapy with minimal invasion. This thesis presents the design, fabrication, and application of specialty fibers for all-in-fiber sensing and light generation with high performance. Further investigations on the integration of all-in-fiber light generation with chemical or biological analysis will be carried out in the near future.