Study On Fiber Lasers And Their Properties Incorporating Nonlinear Effects

Fiber laser technology is an important subdiscipline of modern optics, due to their many applications in optical fiber communications, optical fiber sensing, nonlinear optics, biophotonics, femtochemistry and so on. This dissertation studies fiber lasers and their properties incorporating nonlinear effects, both experimentally and theoretically. The primary coverage involves generation and tuning of ultrashort optical pulse, high sensitivity third-order autocorrelation measurement, multi-wavelength fiber laser, single-longitudinal-mode fiber laser and its applications, Brillouin fiber laser, and2μm thulium-doped fiber laser.To begin with, the thesis introduces fiber laser technology and its close relationship with nonlinear optics. The history of fiber laser is presented, as well as a brief introduction of various fiber nonlinear effects. The section arrangement and major innovations are then summarized.Then, technologies of ultrashort optical pulse generation, wavelength and repetition rate tuning, and autocorrelation measurement are investigated. Based on an actively mode-locked fiber laser and soliton self-frequency shift (SSFS) in a single mode fiber, an all-fiber widely repetition-and wavelength-tunable pulse generator is demonstrated. We also achieve tunable high-energy soliton pulse generation from a large-mode-area fiber, which is pumped by a picosecond time-lens source. The disadvantages of existing autocorrelation measurement technologies are discussed, and we propose a solution based on intensity modulation and third harmonic detection. High sensitivity measurement of three-photon-absorption autocorrelation is demonstrated at the telecommunication wavelength of1558nm, a wavelength regime where a mixture of two-photon-absorption and three-photon-absorption is present.Furthermore, several important fiber lasers are studied and employed in applications, such as optical microwave generation and Brillouin-based distributed fiber sensing. Multi-wavelength erbium-doped fiber lasers based on four wave mixing effect are introduced, and a double-pumped multi-wavelength fiber optical parametric oscillator is proposed for the first time. By incorporating a bismuth-based erbium-doped fiber, an L-band (1565-1625nm) Brillouin fiber laser is achieved. We demonstrate1940nm to2010nm continuous CW wavelength-tuning in a thulium-doped fiber laser, using only fiber-format components. This fiber laser employs a Fabry-Perot filter and can operate as a wavelength-swept source. We propose a wavelength tunable dual-wavelength single-longitudinal-mode (SLM) fiber laser, by employing saturable absorber and fiber Bragg gratings (FBG). A FBG pair (FBGP) with ultranarrow transmission band is also fabricated and employed to achieve dual-wavelength SLM fiber laser. The FBGP based fiber laser is then used in the application of optical microwave generation. A novel method to measure Brillouin frequency shift for Brillouin-based sensing application is then demonstrated, by incorporating a SLM fiber laser.Finally, the article gives a summary and discusses the shortcomings of the research work. The research plans for the future are also introduced.