TbFeCo磁光薄膜飞秒激光感应超快磁化动力学研究

利用时间分辨磁光克尔光谱技术,研究TbFeCo磁光薄膜飞秒激光感应超快磁化动力学过程。观测到亚皮秒的超快退磁过程,符合"三温度"模型中由电子-自旋散射引起的超快退磁机制。磁化动力学的激发功率流密度依赖关系结果表明,随着激发功率流密度的增大,超快退磁程度增加和磁化恢复时间延长,符合"三温度"模型的解释。在衬底厚度不同的TbFeCo样品对比实验中发现,同功率流密度激发下衬底较薄的样品退磁程度更高,磁化恢复速率更快。     

Ag底层对TbFeCo薄膜磁性能的影响

采用射频磁控溅射法在玻璃基片上制备了TbFeCo/Ag非晶垂直磁化膜，研究了Ag底层厚度对TbFeCo薄膜磁性能的影响。原子力显微镜、振动样品磁强计与磁光盘测试仪测量结果表明：薄的银底层具有较高的表面粗糙度可以显著增大TbFeCo薄膜的矫顽力，改善TbFeCo薄膜的磁光温度特性，该薄膜有望用作高密度垂直记录介质与光磁混合记录介质。     

SmDyFeCo磁光薄膜的磁特性研究

采用射频磁控溅射方法制备了ＳｍＤｙＦｅＣｏ非晶磁光薄膜，研究了氩气压，溅射功率对ＳｍＤｙＦｅＣｏ薄膜磁特性的影响。实验表明，和ＤｙＦｅＣｏ非晶薄膜相比，ＳｍＤｙＦｅＣｏ非晶薄膜的矫顽力Ｈｃ随温度变化更为缓慢，并且具有更大的垂直磁各向异性常数，因而具有更好的记录特性，本征磁光克尔角可达０．３１，可以作为一种实用化的磁光记录介质。     

p型Na掺杂ZnMgO薄膜的光电导性能

采用脉冲激光沉积(PLD)方法在石英衬底上制备p型Na掺杂ZnMgO薄膜,薄膜在氮气气氛中600℃退火60s,具有较好的光电性能。在室温下分别用波长254nm的紫外光和波长630nm的红色激光对样品进行了光电导性能测试。两种光照下,光电流均瞬间上升,且光响应度与外加偏压具有线性相关性。紫外光照下p型Na掺杂ZnMgO薄膜的光电流变化比红色激光照射下要显著。     

采用准分子激光退火的室温沉积ITiO薄膜的性能研究

采用室温磁控溅射的方法在玻璃衬底上沉积掺Ti氧化铟薄膜,并在真空中采用XeCl准分子激光进行退火,样品的光学、电学性能、相结构分别采用分光光度计、霍尔效应测试仪和X射线衍射仪进行测试。结果表明,功率为100~150mJ/cm2的准分子激光照射可以使薄膜由无定形态转变为结晶态,激活所掺杂的Ti原子,降低薄膜的电阻率;增大退火功率还可以进一步降低载流子浓度,提高薄膜的透过率。经150mJ/cm2准分子激光退火的掺Ti氧化铟薄膜,其电阻率为6.93×10-4Ω·cm,透过率达到了88.4%。     

激光辐照引起Ge2Sb2Te5非晶态薄膜的电/光性质变化

研究了激光辐照引起Ge₂Sb₂Te₅非晶态薄膜的电/光性质变化, 当激光功率为580mW时薄膜的方块电阻有四个数量级(10⁷～10³Ω/□)的突变; 对电阻发生突变前、中、后的三个样品进行了XRD测试, 结果表明, 随着激光功率的增大,薄膜由非晶态向晶态转变,用椭偏仪测试了结构转变前、中、后三个样品的光学常数, 在可见光范围内薄膜的光学常数在波长相同情况下有: n_非晶态>n_中间态>n_晶态, k_晶态>k_中间态>k_非晶态, α_晶态>α_中间态>α_非晶态, 结合电阻变化曲线和XRD图谱讨论了激光辐照Ge₂Sb₂Te₅非晶态薄膜的电/光性质变化同激光功率和结构转变之间的关系.     

磁场调制直接重写磁光存储介质的记录特性研究

用直流共溅射方法制备了富稀土－过渡族金属非晶态合金薄膜，用数值计算的方法计算了激光照射下多层膜结构盘片的温度场分布，分析了盘片材料成分和结构对热磁记录的影响，对盘片结构进行了优化设计并选定了合适的磁光层和电介质层厚度。实验盘片可在低偏场和低激光功率下记录，盘片的读写性能基本符合２．５英雨可擦重写磁光盘（ＭｉｎｉＤｉｓｋ）的使用要求。     

La0．88Te0．12MnO3-δ薄膜的结构及光诱导特性研究

用脉冲激光沉积法在LaAlO3衬底上制备了La0.88Te0.12MnO3-δ(LTeMnO)薄膜.X射线衍射分析表明,薄膜具有钙钛矿赝立方结构,且沿(012)方向择优生长;电阻率-温度关系显示样品发生了金属绝缘体转变和庞磁电阻效应,转变温度为278K;在0.4T的磁场下,其磁电阻最大值为16.9%,对应的温度为223K.在绿激光作用下,光致电阻率变化最大值为13.2%;原因可能是激光作用影响了体系中载流子的浓度,进而影响了体系的自旋.     

MOCVD生长温度控制p型InGaN形貌和电学特性提高LED光功率

利用金属有机物化学气相淀积（MOCVD）技术在蓝宝石衬底上生长了InGaN∶Mg薄膜,通过改变外延生长温度优化p型InGaN∶Mg表面形貌和电学特性。在800℃,InGaN的空穴浓度为1.9×1019cm-3,电阻率较低,通过原子力显微镜观察到粗化的样品表面有很多圆丘,其均方根粗糙度是所有样品中最高的,综合粗化的表面和优化电学特性的p-InGaN接触层的LED光功率提高23%。     

亚表面缺陷的实时成像检测

提出一种适合于金属亚表面缺陷的可视化无损检测方法——磁光/脉冲涡流成像方法。该方法以脉冲信号激励产生涡流,以激光对被检测物体的照射取代传统涡流检测的线圈探头,通过磁光传感元件将缺陷引起的磁场变化转换成相应的光强度的变化,由传统的显微镜、照明系统、偏振器和CCD图像传感器组成的光学系统将光强变化转换为“明”或“暗”图像,实现了对缺陷的实时成像检测。本文论述了磁光/脉冲涡流实时成像检测机理,给出了一种实验装置。通过对金属表面/亚表面缺陷实验,表明该检测方法快速、准确,可实现微/纳米级缺陷的成像检测。     

Enhanced Polar Magneto-optical Kerr Rotation in Cobalt Thin Film Incorporating Ag Nanoparticles

We report an experimental study on the effect of Ag nanoparticles on the polar magneto-optical Kerr effect in cobalt thin film. The magneto-optical cobalt thin film was prepared by electron beam deposition method onto the Ag nanoparticles which were synthesized by laser ablation in liquid technique. Our results indicate that we have sufficient enhancement of polar magneto-optical Kerr effect of cobalt thin film around the surface plasmon resonance of Ag nanoparticles. Moreover, combination of surface plasmon resonance of the Ag nanoparticles and very thin Au layer can be attained the enhancement factor in all of visible spectral region.     

Magneto-Plasmonic Effect in Cobalt Thin Film Incorporating Core–Shell Ag@Au Nanoparticles

We report enhanced magneto-optical Kerr rotation in the magneto-plasmonic structure of a cobalt thin film incorporating silver/gold core–shell nanoparticles. Metallic nanoparticles with core–shell structure of silver/gold were fabricated by laser ablation in liquid method and the magneto-optical medium was prepared by electron beam deposition technique. Excitation of localized surface plasmon resonance was demonstrated for various incidence angles. The experimental results show direct evidence for localized surface plasmon resonance enhancement effect on the polar magneto-optical Kerr effect of the cobalt thin film.     

Thermodynamic simulation of magnetic-field-modulation methods for pulsed laser irradiation in magneto-optical disks

Direct overwrite magnetic-field modulation recording with dc and pulsed laser irradiation in a magneto-optical disk was simulated thermodynamically. Because the laser light heats the magnetic film, which allows the magnetization to be reversed, the waveform of the laser light strongly affects the shape of the magnetic domain. The dynamic temperature changes in magnetic thin films are simulated for dc and pulsed laser irradiations. With pulsed irradiation the heat is constrained within a limited area, which results in jitter-free magnetic domains, high optical efficiency, and high tracks-per-inch and bits-per-inch recordings.     

基于外加热激励源的中红外激光辐照VO2薄膜温升研究

VO_2薄膜在中红外激光防护领域有着重要意义。为研究中红外激光辐照VO_2薄膜的温升累积效应及克服中红外激光器功率过小的困难,设计了一种外加热激励源的实验方法。首先利用ANSYS软件对中红外纳秒脉冲激光在不同激励源温度和不同功率密度下辐照VO_2薄膜的温升累积进行仿真,并做了实际验证。研究发现,随着外加激励温度的升高,可在一定时间(100s)内达到VO_2相变温度的激光功率密度逐渐减小,通过增加功率密度,也可以进一步降低相变所需的激励源温度。两者均提高了VO_2薄膜的温升速率。然后在激励源温度为40℃、中红外激光功率密度为1 W/mm~2的条件下研究了中红外纳秒脉冲激光参数对VO_2薄膜的温升累积效应,结果表明,增加激光脉宽、增加重频或光斑半径均能有效增加VO_2薄膜的温升速率。     

Tb-Fe-Co磁光薄膜溅射条件对Kerr转角的影响

在实际磁光盘生产线上大都使用合金溅射靶溅射记录介质膜,而尚示有直接使用合金靶研究这些关系的报道。我们首先研究了用于磁光油射的系列合金靶,并完善了靶材制造工艺参数,且在此基础上进行了成分以及溅射参数对各种磁光性能影响的研究。首先确定了各种溅射和N2－Ar气流量下Al、Si以及Tb-Fe-Co(Mo）的溅射速率,在此基础上通过改变溅射功率和调整气汉量改变SiN的成分和厚度,在各种功率和气流量下溅射了Mo膜,并测定了这些磁光膜的Kerr线以获得Kerr转角等性能,从而探讨了溅射工艺条件对Kerr的影响。     

Magneto-Optical Faraday Rotation in Ce:YIG Thin Films Incorporating Gold Nanoparticles

We report an experimental study on optical and magneto-optical properties of Ce-substituted yttrium iron garnet thin films incorporating gold nanoparticles. Au nanoparticles were formed by heating Au thin film on cubic quartz and garnet substrates in a vacuum chamber and a Ce:YIG layer was deposited on them by the aid of the pulsed laser deposition method. A large enhancement of the Faraday rotation was obtained in the sample with Au nanoparticles on a quartz substrate and the effect of the substrate material on improving the optical and magneto-optical response of samples were investigated.     

Generation of soliton and bound soliton pulses in mode-locked erbium-doped fiber laser using graphene film as saturable absorber

We report an observation of soliton and bound-state soliton in passive mode-locked fibre laser employing graphene film as a passive saturable absorber (SA). The SA was fabricated from the graphene flakes, which were obtained from electrochemical exfoliation process. The graphene flakes was mixed with polyethylene oxide solution to form a polymer composite, which was then dried at room temperature to produce a film. The film was then integrated in a laser cavity by attaching it to the end of a fibre ferrule with the aid of index matching gel. The fibre laser generated soliton pulses with a 20.7 MHz repetition rate, 0.88 ps pulse width, 0.0158 mW average output power, 0.175 pJ pulse energy and 18.72 W peak power at the wavelength of 1564 nm. A bound soliton with pulse duration of ~1.04 ps was also obtained at the pump power of 110.85 mW by carefully adjusting the polarization of the oscillating laser. The formation of bound soliton is due to the direct pulse to pulse interaction. The results show that the proposed graphene-based SA offers a simple and cost efficient approach of generating soliton and bound soliton in mode-locked EDFL set-up.     

Finding stabilized coercivity in a study of thickness and temperature dependent Co/Ag/Ge(001) ultrathin films

Epitaxial magneto-optical Co/Ag/Ge(001) ultrathin films were investigated at both room temperature and low temperature. Interesting variations in coercivity as a function of thickness and temperature suggest the existance of interfacial exchange interactions. The operative Ag layers required to inhibit intermixing of Co-Ge alloys from the oscillation of coercivity with Ag film thickness were determined. When the Ag film thickness was reduced to the submonolayer range, perpendicular anisotropy was unexpectedly found. Thus unusual phenomenon can be qualitatively discussed in terms of effective magnetic anisotropy by the contribution of reduced Co layers and by surface magnetic anisotropy.     

Comparative characteristics of magneto-optical materials

Experimental results of measurements for Russian magneto-optical glasses MOG101, MOG105, MOG04, and MOG10 are presented, including the coefficient of electronic nonlinearity, energy of thermal defocusing, and power resistance. For comparison, the same parameters are shown for the optical glass K8 (an analog of the well-known BK7 glass), the fused silica QU-1, and the laser phosphate glass GLS-22P. The obtained data allow consumers to choose the proper magneto-optical materials for the device operation mode.     

钇钡铜氧超导薄膜光诱导弛豫特性研究

采用TFA-MOD法在LaAlO3(LAO)单晶基底上制备了钇钡铜氧(YBCO)超导薄膜,利用X射线衍射对YBCO超导薄膜的结构进行了表征,并对其最佳沉积工艺进行了分析;研究了YBCO薄膜在不同温度和不同光功率下的光诱导特性.在光诱导下,YBCO薄膜出现了明显与电子体系相关的弛豫现象,说明薄膜的光致电阻变化与激光的功率...