| This thesis focuses on the fabrication and analysis of miniature functional devices that can be used for different sensing and detection applications. As the first step, the surface characteristics and morphology of the micro/nano structures on substrates (fused silica and silicon) fabricated in water and in air by femtosecond laser were investigated. Based on this study, three micro devices have been designed and fabricated by femtosecond laser, and they were analyzed for optical and chemical sensing and detections. The three micro devices are: 1) an optical Fabry--Perot interferometer in optical fiber (made from fused silica) with smooth cavity surfaces. The Fabry--Perot interferometer was used to measure accurately the refractive index of solution and, hence, is capable of identifying different solutions; 2) a fused silica glass substrate for surface enhanced Raman spectroscopy (SERS). The optimized morphology (in nano/micron scales) on the fused silica surface with post chemical silver planting which can achieve a cross-section enhancement factor (EF) of 2.5 x 106, evaluated by 10-7 M Rhodamine 6G solutions; 3) a nanostructured silicon substrate for the surface-enhanced Raman scattering application. A simple and efficient method was developed to fabricate a substrate that was pre-coated with silver nitrite film to generate silver nanoparticles over a large--area. This study demonstrates that an EF greater than 5 x 105, measured by 10-6 M Rhodamine 6G solutions can be achieved. The proposed fabrication techniques and miniature devices can be used to integrate the SERS capability into a microchip (lab-on-a-chip) for biomedical and chemical analysis. |
