Lim, Kok Sing (2012) Investigation of fabrication techniques, characteristics and applications of microfiber devices / Lim Kok Sing. PhD thesis, University of Malaya.
Abstract
Microfiber devices have great potential in numerous applications as they offer a number of unique characteristics and optical properties. In this thesis, the background theory and fabrication techniques of microfiber devices are introduced. A high precision computer-controlled rig based on flame brushing technique was assembled in the laboratory. It is capable of producing tapered fibers with a maximum length of ~230 mm and a minimum waist diameter of ~ 400 nm. Two methods to provide long term protection to the tapered fibers and microfiber devices are demonstrated. The first method is to embed the microfiber device in a low-index resin while the second method involves encasing the long tapered fiber in an acrylic casing to provide the tapered fiber a clean and dry ambient. Microfiber devices such as Microfiber Loop Resonators, Microfiber Knot Resonators and Microfiber Mach-Zehnder Interferometer were produced. Application of Microfiber Loop Resonator as optical filter in multiwavelength laser was investigated. The lasing quality can be enhanced by manipulating the state of polarization to improve the resonance extinction ratio of the Microfiber Loop Resonator. Microfiber resonators also exhibit unique thermal characteristics. As a temperature sensor, investigation indicates that the extinction ratio and resonance wavelength varies by 0.043 dB/oC and 50.6 pm/°C respectively with the temperature change. In addition, a compact current sensor based on a copper wire wrapped around a Microfiber Knot Resonator has been devised. The resonance wavelength varies when electric current flows through the copper wire. The wavelength shift is due to thermally induced optical phase shifts, a result of heat produced by the flow of current. A tuning slope of 51.3 pm/A2 has been achieved with the single-wire configuration.
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