【作者】 张斌；

【导师】 姜宗福； 侯静；

【作者基本信息】 国防科学技术大学 ， 光学工程， 2012， 博士

【摘要】 超连续谱激光光源不仅具有传统白光光源的宽光谱特性，还具有高亮度和高相干性，因此在基础科学、工业、通信及医学等众多领域都有着重要应用。近十年来，随着光子晶体光纤的出现，针对超连续谱光源的研究取得突飞猛进的发展。虽然石英光子晶体光纤中产生的超连续谱已超过两个倍频程，但是在超连续谱光谱控制、可见光及中红外超连续谱产生等方面的研究却相对滞后，成为目前超连续谱研究领域的热点。论文主要围绕可见光超连续谱产生及光谱控制、中红外超连续谱产生以及光纤放大器中超连续谱产生等问题展开理论和实验研究。主要内容包括：1.设计了带隙覆盖整个可见光波段的低损耗全固态光子带隙光纤，并应用于可见光超连续谱的产生及光谱控制。设计了低损耗全固态光子带隙光纤，第一阶带隙覆盖整个可见光波段。对所拉制的全固态光子带隙光纤，通过数值计算和实验测量获得其第一阶带隙范围为0.45~0.9μm，零色散波长为0.816μm。因此数值和实验研究了800nm附近可调谐飞秒脉冲泵浦全固态光子带隙光纤时超连续谱的产生，光谱展宽范围为0.68~0.9μm，长波边受到光子带隙的抑制。改用532nm的亚纳秒激光泵浦，产生的超连续谱被很好地控制在带隙范围内，光谱展宽范围为0.53~0.9μm。2.设计了氟化物、碲化物以及硫化物玻璃光纤，并数值模拟这些光纤中超连续谱的产生，分析光谱展宽到约5μm的可行性。计算ZBLAN单模光纤的各种光学参数，包括Raman响应函数，数值计算和实验测量表明ZBLAN单模光纤的零色散波长为1.49μm，因此选用1.55μm和2μm脉冲作为泵浦源，数值模拟了不同脉冲宽度和峰值功率下所产生的中红外超连续谱，结果表明脉冲宽度的增加可降低对峰值功率的要求，更容易将中红外超连续谱展宽到5μm；设计零色散波长在1.55μm以下的碲化物悬吊芯微结构光纤和在2μm以下的无截止单模光子晶体光纤，分别选择1.55μm和2μm脉冲激光作为泵浦源，数值研究证实采用悬吊芯微结构光纤，更容易将超连续谱展宽到5μm，而无截止单模光子晶体光纤在确保大功率和高光束质量的条件下，也能产生700~5000nm范围的超连续谱；设计非线性系数更高的As2S3悬吊芯微结构光纤，将零色散波长移到2μm以下，数值研究表明采用2μm皮秒脉冲泵浦，峰值功率只需500W，在15cm长的光纤内便可产生800~5000nm的中红外超连续谱。这种光纤的高非线性系数降低了对泵浦光的要求，可应用于紧凑的低阈值中红外超连续谱光源。3、在全光纤铒镱共掺双包层光纤放大器中，实现了8W光谱无畸变的纳秒脉冲输出。搭建基于半导体可饱和吸收镜的被动锁模光纤激光器作为种子光源，输出波长为1550nm，脉冲宽度为1ns。在各放大级中加入带通滤波器抑制输入信号光中的ASE噪声，同时采用掺铒光纤放大器与铒镱共掺双包层光纤放大器的混合结构，提高调制不稳定性发生的阈值，实现了1550nm波长的纳秒脉冲输出，平均功率达8W，光谱无畸变，边模抑制比达40dB。4、在铒镱共掺双包层光纤放大器对种子脉冲进行放大的过程中，直接产生平坦的超连续谱输出，并通过级联的铥钬共掺光纤放大器，将光谱扩展到中红外波段。利用调制不稳定性效应，使纳秒脉冲在铒镱共掺双包层光纤放大器中产生分裂，并出现非线性光谱展宽，光谱从1530nm展宽到1700nm以上，覆盖了通讯波段中C-band到U-band的整个范围。采用峰值功率更高的纳秒脉冲半导体激光作为种子光，经铒镱共掺双包层光纤放大器后，光谱可展宽到2μm以上，再通过级联的铥钬共掺光纤，产生了1.75~2.6μm的平坦中红外超连续谱输出。更多还原

【Abstract】 Supercontinuum laser sources have broad spectra as traditional white light source,in addition they have high brightness and coherences, and therefore they have a widevariety of applications in fundamental science, industry, optical communication andmedicine. In the recent decade, the researches on supercontinuum source havedeveloped rapidly with the advent of photonic crystal fibers (PCF). Althoughsupercontinuum sources extend over two octaves in silica PCF, the studies oncontrolling of spectra broadening of supercontinuum, visible supercontinuum generationand mid-IR supercontinuum generation still lag behind. These issues have attractedconsiderable attention in the area of supercontinuum generation. In this thesiscontrollable visible supercontinuum generation, mid-infrared supercontinuumgeneration and supercontinuum generation in fiber amplifiers are investigated in theoryand experiment in thus thesis. The primary contents are presented as follows:1. The low loss all-solid photonic bandgap fiber (AS-PBGF) whose bandgapcovers the whole visible light region is designed and applied in controllable visiblesupercontinuum generation. The AS-PBGF is designed and its first bandgap covers thewhole visible light region. The bandgaps and the group velocity dispersion of thefabricated AS-PBGF are studied through numerical simulation and experiment. The firstbandgap covers from around0.45to0.9μm, and the zero-dispersion wavelength (ZDW)is0.816μm, therefore, supercontinuum generation in this fiber pumped by a tunablefemtosecond laser operating around800nm is studied experimentally and numerically.The output spectrum covers the range from0.68to0.9μm and the long wavelengthedge is suppressed by the photonic bangap. The supercontinuum from0.53to0.9μm isobtained using sub-nanosecond pulses from532nm microchip laser and its longwavelength reaches the edge of the bandgap. The generated visible supercontinuum isrestricted in the bandgap.2. Fluoride, tellurite and chalcogenide glass fibers are designed, and thesupercontinuum generation in these fibers are investigated by numerically. Thefeasibilities of extending the spectrum to around5μm are analyzed. The opticalparameters of single-mode ZBLAN fiber are calculated, including Raman responsefunction. Numerical calculation and experimental measurment confirm that the ZDW ofthe single-mode ZBLAN is1.49μm, and therefore the lasers operating at1.55μm and2μm are used to pump the ZBLAN fiber in the simulations. The supercontinuumgeneration is numerically simulated with different peak power and pulse duration. Fromthe results, it can be concluded that the longer pulse can relax the requirement of peakpower and readily broaden the spectra to5μm. Suspended core tellurite microstructuredoptical fiber (MOF) and endlessly single-mode tellurite PCF are both designed and the ZDWs are below1.55μm and2.0μm respectively. These fibers can be used for mid-IRsupercontinuum generation pumped by fiber lasers operating at1.55μm and2.0μmrespectively. Numerical studies demonstrate that the supercontinuum readily extends tonear5μm in suspended core MOF. And the endlessly single-mode fiber is appropriatefor high power mid-IR supercontinuum generation ranged from700nm to5000nm andthe endlessly single-mode property can ensure high beam quality. Suspended core MOFmade of As2S3with higher nonlinear coefficient is designed to have a ZDW below2.0μm. The numerical results indicate that500W peak power is enough to achievemid-infrared supercontinuum covering800~5000nm through15cm As2S3MOFpumped by picosecond pulse at2.0μm. The high nonlinear coefficient of As2S3MOFreduces the demand of pump laser, and this kind of fiber can be applicable to compactlow-threshold mid-IR supercontinuum source.3. An8W nanosecond pulsed laser without distortions in spectrum is achieved inall-fiber Er/Yb co-doped double-clad fiber amplifier (EYDFA). A1550nm passivemode-locked fiber laser based on semiconductor saturable absorber mirror is built andthe output pulse width is around1ns. The nanosecond pulse is amplified in the hybridEr doped fiber amplifier (EDFA) and EYDFA successionally. The band pass filters areused to suppress the noise in input signal in each stage of the amplifier, thus thethreshold of modulation instability is increased. The nanosecond pulse at1550nm withaverage power of up to8W is achieved, and the feature of MI and any other significantnonlinearity distortions are not observed in the spectra. The side-mode suppression ratiois up to40dB.4. In the process of amplification of the seeded pulse in EYDFA, thesupercontinuum is generated directly from the fiber amplifier and extended tomid-infrared region by Tm/Ho co-doped fiber amplifier (THFA) in succession.Nanosecond pulse fission occurs initiated by modulation instability when it is amplifiedin EYDFA, and the spectrum is broadened due to nonlinear effects and extended from1530to above1700nm covering the total C-band to U-band in communication. AnEYDFA is used to amplify a nanosecond seeded pulse with higher peak power fromelectric modulated laser diode, and the output spectrum extends beyond2μm. A pieceof cascaded THDF is employed to gain flat mid-infrared supercontinuum from1.75μmto2.6μm.更多还原