| The ultra short pulse laser is so special in time domain, so that it has been widely used in areas like micro-machining, medical tomography, high resolution spectroscopy, detection and so on. However, there are little companies provide product like ultra-short pulse fiber laser, we want to develop a laser that can be directly transformed into a product ourselves. The industrial need for a product is extremely stable and reliable. Based on these needs, we used semi-conductor saturable absorber mirror(SESAM) as a passive mode-locked device, ytterbium doped fiber as gain material, fiber bragg grating(FBG) as a output mirror to develop a simple-structured robust all-fiber structure ultra-short pulse fiber laser. The main contents of this dissertation is as follow:(1) Briefly introduced the advantages of fiber laser and applications of ultra-short pulse laser. We provide the common ways to achieve passive mode lock in fiber laser and their advantages and disadvantages. The macroscopic properties of SESAM and their influence to mode lock process is introduced.(2) Theoretical, in order to study the property when a pulse is transmitted in a fiber, the nonlinear Sch?dinger(NLS) equation is deducted from Maxwell equations. And we used NLS to numerical study the dispersion and non-linear effects in fiber.(3) Experimentally, a 6.3mW, 9ps duration and repetition rate 30 MHz pulse is achieved using SESAM passive mode lock technology. We provide the pictures when the mode lock process is founded. We studied the influence to the output when using different FBG, finding out that using short bandwidth FBG is easier to realize mode lock. The impact to output using different length of gain fiber is also studied and we find the most feasible length of fiber, these can be useful when we choose the appropriate devices in the future. Finally, the amplification property of a pulse is studied, and we achieved 24.4mW amplified output. |
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