【作者】 刘伟；

【导师】 沈永行；

【作者基本信息】 浙江大学 ， 光学工程， 2012， 硕士

【摘要】 激光器的全光纤化是近年来激光器的一个重要研究方向,全光纤化激光器由于结构简单、环境影响小等优点,在光纤传感、光谱学、工业加工等领域都有着重要的应用。本文以掺Yb增益光纤和Bi/Cr共掺石英光纤为实验基础,研究了包括全光纤化可饱和吸收调Q技术、基于SBS快速被动调Q技术、超连续谱产生技术在内的新型光纤激光器技术。采用12cm长度的Bi/Cr石英光纤为可饱和吸收体,研制了基于光纤化可饱和吸收体(FSA)的被动调Q掺Yb光纤激光器,在5.6W泵浦功率下,获得了2.7W的调Q脉冲输出。脉冲宽度约为500ns,重复频率为50kHz。通过在15m长度的Yb增益光纤和一对光纤光栅对组成的线性谐振腔内直接熔接一段Bi/Cr共掺石英光纤,在975nm的半导体激光器连续泵浦下,实现了高重频的高峰值功率亚纳秒短脉冲激光输出。本文对受激布里渊散射效应快速调Q作用进行了阐述。实验结果表明,输出激光的重复频率与吸收的泵浦光功率成线性关系；脉冲激光峰值功率超过30kW；在吸收泵浦功率为8.2W时,光纤激光器获得了重复频率最高为50.2 kHz、平均功率为2W的亚纳秒脉冲激光输出。在此基础上,采用MOPA结构对600mW的激光种子进行了放大,功率放大至4W。采用结构极为简单的腔内非线性转换结构,以Bi/Cr共掺石英光纤为非线性转换介质,通过光纤中受激布里渊散射、受激拉曼散射、四波混频等各种非线性机制等共同作用,获得了光谱范围覆盖1060nm到2200nm,在1100nm至2000nm内光谱平坦度优于5dB的超连续谱。最后分析了实验相关的物理机理以及Bi/Cr石英光纤长度、泵浦功率对输出光谱的影响。更多还原

【Abstract】 All fiberized laser technology is one of the most important technologies in laser, due to its important application in optical fiber sensing, optical fiber communications, manufacture industry and so on. This thesis focuses on research of all fiberized fiber laser technologies, which include passively Q-switched fiber laser with FSA, quick passively Q-switched fiber laser based on SBS effect and supercontinuum generation in Bi/Cr co-doped fiber.A novel Bi/Cr co-doped fiber acting as a saturable absorber has been demonstrated. By splicing 12cm Bi/Cr co-doped fiber in a laser cavity, we achieved a passively Q-switched fiber laser. Pulse output at 1061nm was obtained with around 500ns pulse duration and more than 50% optical to optical conversion efficiency.We also demonstrates a novel all-fiberized Yb doped fiber laser configuration for passively subnanosecond pulse generation. By splicing a piece of short Bi/Cr codoped silica fiber to a section of Yb doped double cladding fiber of 15 meters in a fiber Bragg grating constructed fiber laser cavity, stable subnanosecond pulse train was experimentally obtained with a maximal repetition rate of 50.2 kHz and an average power output of 2W. The caculated peak power exceeded 30kW. The linear dependence of the pulse repetition rate on the absorbed pump power was confirmed. It was also found that the Stimulated Brillouin Scattering plays a crucial role in the pulse generation.A supercontinuum source has been demonstrated with Bi/Cr co-doped fiber. Broadband infrared supercontinuum emission was detected via the Bi/Cr fiber end, which spanned over 1000 nm with spectral intensity variation lower than 5 dB.更多还原