A Stable Packaged Microfiber Coil Resonator for Refractive Index Sensing and Its Long-term Stability Improvement

• Main Authors: Xuan-Yi Lu, 呂宣毅
• Other Authors: Lon Wang
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/zvc56h

碩士 === 國立臺灣大學 === 光電工程學研究所 === 105 === Recently, microfiber coil resonators (MCR) have attracted much attention in nonlinear optics and optical sensing. Compared with the semiconductor based micro resonators, MCRs have attractive properties such as low propagation loss and easy connection with conventional optical fiber devices through their tapered sections. Moreover, by increasing coil turns or stacking microfiber turns, MCRs can achieve very high quality factor. However, an unpackaged MCR is easily affected by surrounding disturbance, which limits its applications. Therefore the methods to protect MCRs is the main focus of this work. In this work, we firstly introduce fabrication process and protection method of MCR. A 3-μm diameter microfiber was produced by using a modified miniature fiber drawing tower. The hydrogen oxygen flame was applied as heat source. Then the experimental setup for fabricating MCR is demonstrated. With the extra long working distance objective and CCD, the coiling process could be observed in situ. This helps us early detect the faults during coiling process. The coiling system with good concentricity and stability helps us control the microfiber coil accurately. Polydimethylsiloxane (PDMS) diluted with hexane was used as package material for MCR. Hexane-diluted PDMS has lower viscosity so the microfiber coil could be turned around easily. The quality factor of PDMS-packaged MCR was 5 x 10^5 and could maintain for 5 days. Next, we tried to use PDMS-packaged MCR as refractive index sensor. PDMS-packaged MCR was put in a PMMA structure and glucose solutions were used for different refractive index. The detection limit of PDMS-packaged MCR was about 7×10^-4 RIU. To increase the potential of practical applications, long-term stability of MCR was further improved by protecting microfibers with UV glue. The performance of MCR could maintain over a month without degradation.