Novel femtosecond laser development with applications in biomedical imaging and photonic device fabrication

Over the past decade, improvements and refinements in the field of ultrafast optics have led to more widespread implementation of femtosecond technology. As applications become more diverse, the development of specialized sources is vital in order to meet the requirements of the experiment. This thesis explores the theory and development of innovative femtosecond lasers and their application in biomedical imaging and photonic device fabrication.; The first part of this thesis focuses on mode-locking and the cavity design theory behind KLM lasers. We explain the mechanisms that enable stable, ultrashort pulses to be produced. The master equation is introduced to provide insight into the interplay between competing nonlinear effects. Based on the operation of a standard laser, we introduce a new cavity design based on the Herriott cell. The theory of multi-pass cavities (MPC) allows for a new class of femtosecond lasers to be built with space-efficient layouts and significant performance enhancements.; Part II of the thesis reports on the development and application of three novel femtosecond sources. The first is an ultra-low threshold KLM laser. The laser has a mode-locking threshold of 156 mW, and produces 14 fs pulses with 200 mW of pump power. We demonstrate the utility of low-threshold technology by developing a portable, robust, and low cost source for biomedical imaging. The 124 nm bandwidth enables ultrahigh resolution imaging of the human retina.; A long cavity laser is also developed. By using the theory of MPC lasers, explained in Part I, pulse energies of up to 150 nJ with 43 fs durations are reported from a 5.85 MHz laser oscillator. This laser serves as the enabling technology for photonic device fabrication in transparent materials. A variety of 2D and 3D devices are fabricated and characterized. The ability to directly write waveguides and structures inside transparent materials is a significant advance over current 2D fabrication techniques.