二极管泵浦掺钕氟化锶无序晶体短脉冲激光特性研究

发布时间：2018-09-14 15:25

【摘要】：具有高功率、宽调谐以及窄脉宽的超快激光在工业精密加工、受控核聚变、光通信、生物医学等领域有广泛的应用前景。探索新型的结构紧凑、性能优异的超快超强光源已经成为科研领域的重要方向。近些年来,随着激光二极管(LaserDiode,LD)制备工艺日益成熟,其直接泵浦的亚皮秒到几十飞秒全固态激光器已经成为激光领域一大研究热点。作为固体激光的重要组成部分,激光晶体材料对激光器性能起到决定性作用。到目前为止,通过自锁模实现几个飞秒激光输出的掺钛蓝宝石(Ti:sappire)晶体仍然是近红外波段(~800nm)应用最广泛的超快晶体材料。但是钛宝石对于泵浦源要求严格,不适合LD直接泵浦,使其结构庞大,维护困难。这也推动着人们寻找新型的激光晶体,期待它既有宽光谱的性质,同时又能克服钛宝石晶体的缺点。近些年来,四能级结构掺钕(Nd~(3+))氟化物无序晶体得到人们关注。多样化的电荷补偿方式产生丰富对称性的晶格结构,使得该类晶体具有非常宽的吸收和发射光谱,有利于LD直接泵浦产生超快可调谐激光。本文主要研究了Nd~(3+)掺杂的氟化锶(SrF_2)无序结构激光晶体光谱特性,以LD端面泵浦方式,研究了新型掺Nd~(3+)氟化锶无序晶体的超快激光特性。主要研究内容如下:1.回顾了超快激光的特点和应用。分析产生超快激光的锁模技术以及测量脉冲宽度的自相关法。阐述全固态锁模激光谐振腔的设计思路。调研了宽光谱掺Nd~(3+)无序结构激光晶体的特点和发展。研究了近些年来应用在超快激光领域的新型纳米材料可饱和吸收体。2.Nd,Y:SrF_2透明陶瓷被动调Q实验研究。基于Nd,Y:SrF_2单晶,采用热压工艺获得Nd,Y:SrF_2激光透明陶瓷。首次实现基于该陶瓷的连续和调Q脉冲激光运转。以Cr4+:YAG为被动调Q开关,获得最短脉宽为169ns,单脉冲能量为19.2μJ的脉冲激光输出。3.Nd,La:SrF_2无序晶体超快激光特性研究。为了打破SrF_2晶体中的Nd~(3+)—Nd~(3+)团簇,向Nd~(3+):SrF_2晶体中共掺适当浓度的缓冲离子La~(3+),获得了宽光谱无序结构的Nd,La:SrF_2激光晶体。首次系统研究了LD端面泵浦Nd,La:SrF_2无序晶体的连续、调谐、被动调Q和连续锁模激光特性。获得了平均输出功率达1.234W,斜效率达50.6%的连续激光输出;连续调谐范围为24.1nm,调谐曲线平滑;研究新型低维纳米材料金纳米双锥的非线性吸收特性,将其作为可饱和吸收材料,实现了最短脉宽为1.15μs稳定的调Q脉冲激光输出;以SESAM为被动锁模元件,获得了稳定的连续锁模激光运转,脉冲半高宽为739fs。4.Nd,Gd:CaF_2/Nd,Gd:SrF_2双波长同步锁模激光研究。将缓冲离子Gd~(3+)共掺到Nd:CaF_2和Nd:SrF_2晶体中,不仅极大的减弱Nd~(3+)团簇效应,还使得它们的晶格格位更为丰富,荧光强度进一步提高,谱线非均匀展宽。Nd,Gd:CaF_2和Nd,Gd:SrF_2晶体具有良好的热学性能和光学性能,其分裂的光谱特点非常有利于双波长或多波长脉冲激光输出。采用LD端面泵浦,以SESAM为被动锁模元件,实现了Nd,Gd:CaF_2和Nd,Gd:SrF_2双波长同步锁模激光运转。双波长同步锁模脉冲激光作为太赫兹波的光源,有重要的研究价值。
[Abstract]:Ultra-fast lasers with high power, wide tuning and narrow pulse width have wide application prospects in industrial precision machining, controlled nuclear fusion, optical communication, biomedicine and other fields. With the development of fabrication technology, direct-pumped sub-picosecond to tens of femtosecond all-solid-state lasers have become a hot research topic in the laser field. As an important part of solid-state lasers, laser crystal materials play a decisive role in laser performance. Titanium-doped blue (Ti-Br) laser output from several femtosecond lasers has been realized by self-mode-locking so far. Ti: Sappire crystal is still the most widely used ultrafast crystal material in the near infrared band (~800nm). However, Ti: Sappire is not suitable for direct LD pumping because of its strict requirements for the pump source, which makes its structure huge and difficult to maintain. The disadvantages of stone crystals. In recent years, four-level neodymium-doped (Nd~ (3+) fluoride disordered crystals have attracted considerable attention. Various charge compensation methods have generated a rich symmetry of the lattice structure, making these crystals have a very wide absorption and emission spectrum, which is conducive to LD direct pumping to produce ultra-fast tunable lasers. The spectroscopic properties of Nd~ (3+) doped SrF_2 disordered laser crystals were studied by LD end-pumping. The main contents are as follows: 1. The characteristics and applications of ultrafast lasers were reviewed. The mode-locking technique for producing ultrafast lasers and the self-measurement of pulse width were analyzed. Correlation method. The design idea of all-solid-state mode-locked laser resonator is described. The characteristics and development of wide-spectrum Nd~ (3+) doped disordered laser crystals are investigated. The saturable absorbers of new nano-materials used in ultra-fast laser field in recent years are studied. Nd, Y: SrF_2 laser transparent ceramics were obtained by hot pressing. Continuous and Q-switched pulse laser operation based on the ceramics was realized for the first time. Nd, La: SrF_2 laser crystals with wide spectrum disordered structure were synthesized by co-doping Nd ~ (3 +) clusters with buffer ions of appropriate concentration La ~ (3 +) into Nd ~ (3 +): SrF_2 crystals. The characteristics of LD end-pumped Nd, La: SrF_2 disordered crystals, such as continuous, tunable, passively Q-switched and continuous-mode lasers, were systematically investigated for the first time. CW laser output with a rate of 50.6%; CW tuning range of 24.1 nm and smooth tuning curve; the nonlinear absorption properties of gold nano-bipyramid as a saturable absorbent material were studied, and the stable Q-switched pulse laser output with a minimum pulse width of 1.15 MS was achieved; and the passive mode-locked element SESAM was used to achieve stable lasing. Continuously mode-locked lasers with half-width of 739 fs.4.Nd, Gd:CaF_2/Nd, Gd:SrF_2 dual-wavelength synchronous mode-locked lasers have been studied. The addition of buffer ions Gd~ (3+) into Nd:CaF_2 and Nd:SrF_2 crystals not only greatly weakens the Nd~ (3+) cluster effect, but also enriches their lattice sites, enhances the fluorescence intensity and broadens the spectral lines unevenly. Nd, Gd: CaF_2 and Nd, Gd: SrF_2 crystals have good thermal and optical properties, and their splitting spectral characteristics are very favorable for dual-wavelength or multi-wavelength pulse laser output. As the light source of terahertz wave, laser has important research value.
【学位授予单位】：山东师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN24

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