高重复频率激光在非掺杂氧化铋玻璃中诱导TiO2晶体析出

使用聚焦后的800nm,150fs,250kHz的高重复频率飞秒脉冲激光研究它在非掺杂氧化铋玻璃内部三维选择性的诱导析晶. 通过拉曼光谱测定发现析出的晶体是TiO2且为金红石相.研究表明, 经过250kHz的飞秒激光辐照一段时间后,玻璃内部由于脉冲能量的连续累积会使得激光辐照区域出现热累积效应,达到玻璃的析晶温度后诱导晶体析出.通过连续移动激光束,可以实现连续刻写TiO2晶线,通过EDX测试显示聚焦区域出现了由于热累积效应而形成热驱动使得离子发生迁徙.实验结果表明这种方法适用于在透明介质材料中三维选择性刻写晶体以制备集成光学器件.     

高重复频率激光在非掺杂氧化铋玻璃中诱导TiO2晶体析出

使用聚焦后的800nm,150 fs,250 kHz的高重复频率飞秒脉冲激光研究它在非掺杂氧化铋玻璃内部三维选择性的诱导析晶.通过拉曼光谱测定发现析出的晶体是TiO2且为金红石相.研究表明,经过250 kHz的飞秒激光辐照一段时间后,玻璃内部由于脉冲能量的连续累积会使得激光辐照区域出现热累积效应,达到玻璃的析晶温度后诱导晶体析出.通过连续移动激光束,可以实现连续刻写TiO2晶线,通过EDX测试显示聚焦区域出现了由于热累积效应而形成热驱动使得离子发生迁徙.实验结果表明这种方法适用于在透明介质材料中三维选择性刻写晶体以制备集成光学器件.     

Ag掺杂对高重复频率飞秒激光诱导Gd_2O_3-MoO_3-B_2O_3玻璃析晶的影响

将800nm高重复频率250kHz的飞秒激光分别聚焦到掺Ag和没有掺Ag的Gd2O3-MoO3-B2O3玻璃表面,研究掺Ag对飞秒激光诱导析晶的影响.对激光辐照的区域显微拉曼分析发现对于没掺Ag玻璃,诱导玻璃析晶需要的激光功率和辐照时间比掺了Ag的玻璃要大要长,这说明Ag的掺入促进了玻璃的析晶.其机理可能为飞秒激光的多光子吸收效应,导致玻璃基质中桥氧键断裂,产生非桥氧空穴和自由电子,玻璃中的Ag离子捕获电离出来的电子被还原成Ag原子,Ag原子在热动力的驱动下移动聚集形成银纳米颗粒,形成的银纳米团簇作为核促进了钼酸盐玻璃的析晶.     

Ag掺杂对高重复频率飞秒激光诱导Gd2O3-MoO3-B2O3玻璃析晶

将800nm高重复频率250 kHz的飞秒激光分别聚焦到掺Ag和没有掺Ag的Gd2O3-MoO3- B2O3玻璃表面,研究掺Ag对飞秒激光诱导析晶的影响。对激光辐照的区域显微拉曼分析发现对于没掺Ag玻璃,诱导玻璃析晶需要的激光功率和辐照时间比掺了Ag的玻璃要大要长,这说明Ag的掺入促进了玻璃的析晶。其机理可能为飞秒激光的多光子吸收效应,导致玻璃基质中桥氧键断裂,产生非桥氧空穴和自由电子,玻璃中的Ag离子捕获电离出来的电子被还原成Ag原子,Ag原子在热动力的驱动下移动聚集形成银纳米颗粒,形成的银纳米团簇作为核促进了钼酸盐玻璃的析晶。     

飞秒激光作用下金掺杂硅酸盐玻璃的光致晶化研究

研究了金掺杂硅酸盐玻璃在飞秒激光辐照和热处理作用下的光致晶化行为，分析探讨了其机理和激光辐照条件的影响.吸收光谱测试表明玻璃内部析出金纳米颗粒. 金纳米颗粒掺杂玻璃在近共振纳秒脉冲作用下显示了强的光限幅效应, 且改变飞秒激光诱导参数可改变该复合玻璃的光学非线性. 关键词： 光致晶化 飞秒激光 金纳米颗粒 硅酸盐玻璃 光限幅     

飞秒激光诱导TiO2金红石相变的激光显微拉曼光谱研究

利用激光显微拉曼光谱仪研究了近红外飞秒激光脉冲诱导TiO2金红石晶体所引起的相变.实验发现当激光的脉冲功率为1.0μJ/脉冲时,随着飞秒激光辐照脉冲数的增加,金红石相的Eg模式强度增强,而A1g模式强度减弱,飞秒激光的非线性效应在晶体内部诱导产生了色心;当激光辐照脉冲数为2.5×106时,锐钛矿石相出现;随着激光辐照脉冲数的增加,锐钛矿相的拉曼振动模式强度增强,金红石相的拉曼振动模式强度减弱.     

不同烧蚀条件下飞秒激光脉冲诱导ZnO纳米结构研究

烧蚀条件对飞秒激光脉冲诱导氧化锌纳米结构有重要影响.研究了800 nm,150 fs,250 kHz的飞秒激光脉冲分别在空气中,去离子水中以及无水乙醇中垂直聚焦于氧化锌晶体表面,诱导形成不同形态的纳米结构.实验结果表明,在空气中利用飞秒激光脉冲辐照样品表面,形成了周期为180 nm的纳米线;在去离子水中辐照诱导形成了由氧化锌纳米线聚集而成的"纳米球";在无水乙醇中形成出现分叉结构的纳米线.拉曼光谱分析辐照前后晶体晶相结果表明,形成的纳米结构相对于辐照前特征峰437 cm-1强度有所下降,在570 cm-1处的峰值则显著增强.分析了在各种烧蚀条件下诱导形成纳米结构的演化过程以及物理机理.     

飞秒激光诱导硒化锌晶体表面自组织生长纳米结构

 以250 kHz高重复频率钛宝石飞秒激光聚焦到硒化锌晶体表面,利用扫描电子显微镜观测飞秒激光辐照后晶体的表面结构。发现线偏振激光辐照的区域形成了自组织周期性纳米结构,其周期为160 nm左右,并且可以通过改变激光的偏振方向调节纳米光栅结构的取向;当晶体相对于激光光束以10 mm/s速度移动,经激光扫描后,在晶体表面形成了长程类布拉格光栅。当飞秒激光光束为圆偏振光时,辐照区域形成均匀的纳米颗粒。     

飞秒激光诱导玻璃内析出BaTiO3晶体

使用800nm、120fs、200kHz的高重复频率超短脉冲激光照射BaO-TiO2-SiO2系玻璃，玻璃经飞秒激光照射数秒钟后，激光会聚点的发光由800nm波长的红色突然转变为非常强的400nm的蓝色，对激光辐照点的发光光谱和X射线衍射分析表明，具有倍频效应的BaTiO3晶体已经产生。     

单次飞秒激光脉冲在玻璃内部产生多次微爆的研究

在入射能量不同的情况下，用近红外飞秒激光脉冲在重钡火石玻璃（ZBaF15）内部产生了色心和微爆，在熔融石英的内部产生了多次微爆现象.实验表明：入射能量较高时，色心的中间会产生微爆；在松聚焦条件下，一个飞秒激光脉冲在透明介质内会激发多次微爆.基于飞秒激光脉冲在透明介质内的自聚焦效应和自由电子等离子体的自散焦效应，理论分析了多次微爆产生的原因；也讨论了飞秒激光脉冲诱导玻璃折射率改变的机理.     

Space-selective growth of frequency-conversion crystals in glasses with ultrashort infrared laser pulses

We report on space-selective growth of a second-harmonic-generation beta-BaB(2)O(4) (BBO) crystal inside a BaO-Al(2)O(3)-B(2)O(3) glass sample at the focal point of an 800-nm femtosecond laser beam. A spherical heated region was formed during the focused laser irradiation through observation with an optical microscope. We moved the heated region by changing the position of the focal point of the laser beam relative to the glass sample. We grew BBO crystal continuously in the glass sample by adjusting the moving speed of the heated zone. Our results demonstrate that functional crystals can be formed three dimensionally in glasses by use of a nonresonant ultrashort pulsed laser.     

高重复频率飞秒脉冲激光诱导钼酸镝玻璃表面析出β′-Dy2（MoO4）3和α-MoO3晶体

高重复频率飞秒脉冲激光辐照钼酸镝玻璃表面后,通过显微拉曼测试,发现在辐照区域内形成了含有MoO4四面体结构的β′-Dy2(MoO4)3晶体和含有MoO6八面体结构的α-MoO3晶体。通过电子能谱(EDS)测量辐照前后样品中钼(Mo)元素的含量,发现在辐照中心位置形成α-MoO3晶体相的区域内出现了明显的Mo元素缺失现象,表明了在高温场作用下,微爆现象引起了材料中心密度的降低。此外,随着辐照时间的增加辐照中心位置还出现了由Dy2(MoO4)3相向MoO3晶体α相的相变。这说明随着激光作用程度的加剧,中心区域Mo元素浓度降低,使得钼氧结构由MoO4四面体向MoO6八面体转变,导致在Mo元素浓度较低的区域更容易形成八面体结构的α-MoO3。     

Femtosecond laser-induced long-lasting phosphorescence in Pr^3＋-doped ZnO-B2O3-SiO2 glass

This paper studies the phenomenon of long-lasting phosphorescence induced by a femtosecond laser in Pr3 -doped ZnO-B2O3-SiO2 glass. With the glass irradiated by a focused femtosecond laser for a short time, the emission of strong reddish long-lasting phosphorescence from the irradiated part of the glass can be observed. The emission peaks are located at 495 and 603 nm in wavelength, showing that the long-lasting phosphorescence originates from the emission of Pr^3 . The intensity of the phosphorescence decreases in inverse proportion to time after the removal of the laser. By analysing the absorption and electron spin resonance spectra of the glass, we find that colour-centres are induced in the glass matrix after the irradiation of the femtosecond laser. A possible mechanism has been provided to account for the generation of long-lasting phosphorescence.     

Sm3+ photoreduction in BaCl2 nanophases precipitated fluoroaluminate glasses under femtosecond laser irradiation

Photoreduction of samarium-doped BaCl(2)-modified aluminofluoride glass by femtosecond laser irradiation and x-ray irradiation were investigated. Photoluminescence of samarium ions indicated that photoreduction of Sm(3+)→Sm(2+) efficiently occurred in glass samples containing more than 5 mol.% BaCl(2) after femtosecond laser irradiation, while dramatic change was not observed by x-ray irradiation. Transmission electron microscope results revealed that BaCl(2) nanophases only precipitated from glass matrix with a high BaCl(2) content by focusing femtosecond laser irradiation. Samarium ions were selectively incorporated into the precipitated nanophases, resulting in the enhancement of Sm(3+) photoreduction under lower laser power.     

High repetition rate femtosecond laser irradiation-induced elements redistribution in Ag-doped glass

A 250 kHz femtosecond laser was used to induce a one-step precipitation of Ag nanoparticles and the simultaneous element redistribution in Ag ion doped glass. After femtosecond laser exposure, a ring-shape region was formed. Besides, as a result of an optical spherical aberration effect, a nonuniform laser intensity distribution along the incident direction caused most of the formed Ag nanoparticles to precipitate in the lower part of cross section of this structure. By an EPMA analysis, the relative concentration of the Ag element was both high in the center and in the boundary of the ring-shape region. These Ag nanoparticles could potentially increase the refractive index in their precipitation regions. We proposed that the induced ion redistribution and the precipitation of Ag nanoparticles should be due to the heat accumulation effect by the high repetition rate femtosecond laser irradiation.     

Micromachining soda-lime glass by femtosecond laser pulses

The physical process of forming a modified region in soda-lime glass was investigated using 1 kHz intense femtosecond laser pulses from a Ti: sapphire laser at 775 nm. Through the modifications induced by the femtosecond laser radiation using selective chemical etching techniques, we fabricated reproducible and defined microstructures and further studied their morphologies and etching properties. Moreover, a possible physical mechanism for the femtosecond laser modification in soda-lime glass was proposed.     

Color center formation in soda lime glass and NaCl single crystals with femtosecond laser pulses

The high instantaneous powers associated with femtosecond lasers can color many nominally transparent materials. Although the excitations responsible for this defect formation occur on subpicosecond time scales, subsequent interactions between the resulting electronic and lattice defects complicate the evolution of color center formation and decay. These interactions must be understood in order to account for the long term behavior of coloration. In this work, we probe the evolution of color centers produced by femtosecond laser radiation in soda lime glass and single crystal sodium chloride on different time scales, from microseconds to hundreds of seconds. By using an appropriately chosen probe laser focused through the femtosecond laser spot, we can follow the changes in coloration due to individual or multiple femtosecond pulses, and follow the evolution of that coloration for a long time after femtosecond laser radiation is terminated. For the soda lime glass, the decay of color centers is well described in terms of bimolecular annihilation reactions between electron and hole centers. Similar processes appear to operate in single crystal sodium chloride. PACS 82.50.Pt; 78.55.Qr; 78.55.Fv; 78.47.+p     

Self-assembled volume vortex grating induced by femtosecond laser pulses in glass

We presented a microfabrication process for optical volume vortex grating inside glass by femtosecond laser pulses. The self-trapped filament of femtosecond laser pulses can induce hundreds μm-long region refractive-index changes in glass. We realized the restructured optical vortex beams using a collimated He–Ne laser beam. The maximum first-order diffraction efficiency was about 19.6%. The volume vortex grating structure fabricated in glass is polarization dependent.