Optical microsphere and microbottle resonator for sensor and laser application / Ummu Umairah Mohamad Ali

Micro-resonators have been attracting attention due to their many advantages including their ability to confine light with high quality factor (Q) and in a small modes volume. They are typically associated with circular-path resonant cavities such as micro-ring, micro-disc and micro-toroid geometry and these resonators can support whispering gallery mode (WGM) operation by creating continuous internal reflection at specific resonant wavelengths. According to the geometrical optic principle, a WGM can be represented by an optical ray transmitted exclusively near the micro-resonator surface due to grazing-angle total internal reflection. When light is evanescently coupled into the micro-resonator via a microfiber, very narrow resonance dip with a full width half maximum (FWHM) on a level of pm appears in the transmission spectrum. The optical WGM device can be applied in many areas including optical sensing and lasing. The aim of this research is to develop a micro scale of resonator as a sensor and laser technology which can create devices that are extremely small sized, ultra-lightweight and have the potential to be manufactured at low cost. In this thesis, two types of resonator micro-sphere (MSR) and micro-bottle (MBR) are fabricated using silica fiber with "soften and compress" method. The MSR and MBR is then characterized by employed some range of wavelength from tuneable laser source. The resonance depth is captured for every MSR and MBR condition. The Q-factor was defined by calculation, which used to identify the quality of resonance depth. The MSR and MBR was then used as sensor to sense different relative humidity (RH). For instance, as the RH increases from 40% to 100%) the microfiber 8um coupled with MSR shows sensitivity of 0.2840 dB/%> with a slope linearity of more than 97.80%) and a limit of detection of 19.132%, while for MBR produces sensitivity 4.7% better than MSR, with a slope linearity of more than 99.46%) and a limit of detection of 18.3781%).