Ultra-Broadband Fiber-Based Optical Supercontinuum Source

Entitled: " Ultra-Broadband Fiber-Based Optical Supercontinuum Source " and submitted in partial fulfillment of the requirements for the degree of Master of Applied Science Complies with the regulations of this University and meets the accepted standards with respect to originality and quality. The supercontinuum (SC) generation has been studied intensively because of its numerous applications, such as in optical coherence tomography, dense wavelength division multiplexing, ultrafast spectroscopy, and frequency metrology. The SC generation is usually obtained using a highly nonlinear fiber pumped by high power lasers. Two typical pump sources are usually used in SC generation: continuous wave (CW) lasers and ultra-short pulse lasers. The multimode CW lasers are considered as the low-cost pump source, while ultra-short pulse lasers with high peak power can induce nonlinear effects easily in SC generation. The two pump sources are both considered in this thesis. The first designed SC source contains two low-cost 975 nm multimode CW laser diodes, Erbium/Ytterbium co-doped fiber (EYDF) and highly nonlinear fiber (HNLF), while the other contains a figure-8 mode locking fiber laser, an Er-doped fiber amplifier and photonic crystal fiber (PCF). For the CW laser pumped SC source, the optical spectrum spanning from 900 nm to more than 2000 nm is generated successfully. The total optical output power of SC source is about 200 mW. Additionally, the internal physic mechanisms and reliability of this ultra-broadband SC source are investigated. The ultra broadband and low-cost are achieved simultaneously in this designed source. For the SC generation using a short pulse laser, PCF attracts the most attention due to its high nonlinearity and flexible dispersion profiles. Here, a picosecond (ps) pulse laser and PCF with flat dispersion are used. We demonstrate a simple and compact all-iv fiber supercontinuum source with smooth and fine-structure-free spectrum from 1200 nm to 1920 nm. Furthermore, the pump peak is not observed obviously in the SC spectrum and SC spectrum flatness is better than 11 dB. Related physical mechanisms are discussed. The stability and relative intensity noise (RIN) are also analyzed. The designed SC source has a high smoothness. In particular, the RIN of the broadband SC is comparable to that of the pump laser source. The two proposed fiber-based optical SC laser sources are simple, compact and practical.