الفهرس 
Introduction .Only 14 pages are availabe for public view
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Abstract
This thesis aims to develop novel alignment-free miniaturized cavity-enhanced spectroscopy techniques on the scale of optical fibers and on the microsystem tech-nologies. To this end, a novel alignment-free active intra-cavity single and dual cou-pler fiber-based cavity-enhanced has been proposed. The former configurations have been studied analytically and numerically. Then, the configurations have been vali-dated experimentally. A simulation model for the enhancement factor in the effective length has been elaborated. The model results have been compared with the experi-mental results. An enhancement factor of 942 has been reached-which is the highest enhancement factor achieved in the fiber-based cavity-enhanced techniques.
In addition to, another alignment-free novel technique based on multi-longitudinal mode laser intensity spectroscopy-enabling to couple higher power to the optical cavity-has been proposed. The effect of the gain saturation on the effective length has been studied analytically and numerically. Besides, a novel RF-frequency based cavity-enhanced spectroscopy technique has been proposed. The technique is based on the detection of high frequency spectroscopic signal to eliminate the flicker noise.
Moreover, microfluidics cavity-enhanced spectroscopy based on MEMS technology has been proposed. The different excitation sources (single mode fiber and multimode fiber) have been simulated by using Fourier optics. In the case of single mode fiber, the cavity’s response has been studied at the different beam waist. While in the case of multimode fiber, the cavity’s response has been studied at a different numerical aperture. Then, the cavity’s response of the standard single mode and mul-timode fiber has been compared. Then, the fabrication process procedures have been discussed and demonstrated. The effect of surface roughness has been elucidated. Then, the design of the microfluidics cavities has been elaborated. Finally, the fabri-cated microcavities chips have been measured and utilized in enhancing the sensitivity of different fluids.
The thesis is divided into six chapters as listed below:
Chapter 1:
This chapter gives a concise introduction, the motivation, the objectives, the major contributions and overview of the organization of the thesis.
Chapter 2:
This chapter presents a literature review of the concepts and state-of-the-art related to cavity-enhanced spectroscopy. This review includes ring resonator theory, the theory of the different state-of-the-art cavity-enhanced techniques, an elaborate comparison between these techniques, and sensing mechanisms incorporated with cavity-enhanced spectroscopy.
Chapter 3:
This chapter investigates cavity-enhanced spectroscopy technique on fiber cavities. A novel dual and single coupler intra-cavity technique have been proposed. The tech-niques have been studied in a passive and active configuration. The analysis of the main factors affecting the effective length for each configuration such as fiber coupler coupling coefficient, spectrum analyzer resolution, large extinction coefficient, wave-length dependent round-trip net gain, and noise sources have been elucidated analyti-cally and numerically. Finally, the experimental results of the different configuration have been discussed and compared.
Chapter 4:
This chapter proposes a novel frequency and intensity-based cavity-enhanced tech-niques using a multi-longitudinal mode laser. Firstly, we present an analytical model for novel techniques. Secondly, the key parameters of each technique have been stud-ied. Thirdly, the proposed configurations have been studied numerically. Finally, the experimental results have been discussed.
Chapter 5:
This chapter investigates extending the cavity-enhanced spectroscopy technique to microfluidics technology scale. Firstly, An simulation model elaborates the effect of the source excitation coherence on cavity response. Secondly, the proposed designs have been studied using the presented model investigating the effect of the different design parameters. Finally, the experimental results have been discussed.
Chapter 6:
This chapter gives the thesis’s conclusions and introduces several recommendations and suggestions for future work.