GaAs半导体激光器腔面高反射涂层的研究

通过对GaAs激光器谐振腔后腔面蒸镀SiO、Au高反射膜工艺过程, 分析涂层特性。反射率由无膜时的32%, 提高到94%以上, 保护了器件端面, 降低阈值电流, 提高激光输出功率和工作寿命。     

半导体激光器腔面全介质涂层的研究

通过对GaAs/GaAlAs激光器谐振腔前、后腔面蒸镀2rO₂和ZrO₂、MgF₂的工艺过程,从理论和实验上分析涂层特性,透射率、反射率分别由无膜时的68%、32%,镀膜后提高到94%、95.0%以上,提高了激光输出功率和工作寿命,保护了器件端面。     

半导体激光器高稳定度系统的研究与设计

半导体激光器(LD)随着温度的增加,阈值电流升高,输出功率下降.为了使半导体激光器输出激光功率稳定,设计了激光器高精度稳功率电路,使用功率MOSFET作为电流控制元件,运用负反馈原理调整输出电流,实现对激光器输出功率的控制.试验结果表明,电路设计合理,响应速度快,输出激光功率长期稳定度可以达到0.1%.     

808nm和980nm半导体激光迭阵波长耦合技术

为提高半导体激光器输出光功率,可将多个半导体激光器输出光束耦合成一束激光直接输出或者由光纤耦合输出,以提高半导体激光源的亮度及光束质量.本文采用波长耦合技术进行激光合束,将两种不同波长的半导体激光束通过非相干技术经波长耦合器件耦合输出以实现大功率高效率输出.介绍了非相干耦合技术中波长耦合原理及关键技术,根据波长需要设计了耦合器件,并自行设计光学系统对光束进行扩束聚焦.实验将808 nm和980 nm两半导体激光迭阵光束通过上述技术进行合束, 最终实现了更高功率输出,耦合效率达70%,光斑大小为3 mm×3 mm,可满足将半导体激光器直接应用于熔覆、焊接等场合的要求.     

氟化氘高能激光系统中的光学薄膜

报道了氟化氘(DF)激光系统腔镜高反射膜、CaF2窗口红外宽带增透膜和共孔径分光镜的研制,并介绍了DF腔镜高反射膜的热畸变和损伤实验测试结果.实验结果表明,DF腔镜高反射膜的损伤阈值大于100kW/cm2,CaF2窗口红外宽带增透膜和共孔径分光镜均经受了200kW激光功率的输出,达到了总体提出的要求.     

氟化氘高能激光系统中的光学薄膜

报道了氟化氘(DF)激光系统腔镜高反射膜、CaF2窗口红外宽带增透膜和共孔径分光镜的研制,并介绍了DF腔镜高反射膜的热畸变和损伤实验测试结果.实验结果表明,DF腔镜高反射膜的损伤阈值大于100kW/cm2,CaF2窗口红外宽带增透膜和共孔径分光镜均经受了200kW激光功率的输出,达到了总体提出的要求.     

氟化氘高能激光系统中的光学薄膜

报道了氟化氘 ( DF)激光系统腔镜高反射膜、Ca F2 窗口红外宽带增透膜和共孔径分光镜的研制 ,并介绍了 DF腔镜高反射膜的热畸变和损伤实验测试结果。实验结果表明 ,DF腔镜高反射膜的损伤阈值大于 1 0 0 k W/cm2 ,Ca F2 窗口红外宽带增透膜和共孔径分光镜均经受了 2 0 0 k W激光功率的输出 ,达到了总体提出的要求。     

基于ZEMAX的激光光束整形技术试验研究

由于半导体激光器的发散角较大且输出的光束光斑是椭圆形,因此需要对其输出的光束进行空间整形,形成一个近似圆形的激光光斑。激光扩束镜就是一种比较简单且非常方便的激光光束整形器件,本文将激光扩束镜作为一个激光整形系统与半导体激光器耦合,形成一个完整的激光光束整形系统。利用ZEMAX光学仿真,并进行室外试验验证,最后对试验结果进行了分析。     

体布拉格光栅外腔倍频半导体激光器研究

为提高绿光激光器的输出特性,设计了一种体布拉格光栅外腔倍频半导体激光器。采用反射型体布拉格光栅作为反馈元件构成外腔半导体激光器,并使用三硼酸锂晶体进行倍频,研究了基频光的光束及光谱特性对倍频光的光束及光谱特性的影响。实验结果表明,使用体布拉格光栅进行外腔锁波时,所得到的倍频光同样能实现窄带宽输出,同时倍频光的远场分布与基频光的远场分布一致。使用衍射效率为10%的体布拉格光栅作为外腔输出镜,可将半导体激光器的输出波长稳定锁定在1 064 nm,所得到的倍频光波长稳定在532 nm附近,光谱线宽压缩至0.4 nm左右,输出功率可达73 mW。     

808nm980nm半导体激光迭阵波长耦合技术

随着半导体激光器在工业、军事、核能等领域的广泛应用,单个半导体激光迭阵的光功率已经不能满足实际需求,这就要求将多个半导体激光器耦合成一束激光,可直接输出或者由光纤耦合输出,以提高半导体光源亮度及光束质量。文章通过采用波长耦合技术进行激光合束,将两种不同波长的半导体激光束通过非相干技术经波长耦合器件耦合输出以实现大功率高效率输出,便于满足工业加工需要。介绍了非相干耦合技术中波长耦合原理及关键技术,根据波长需要设计耦合器件,并自行设计采用光学系统对光束进行扩束聚焦,通过实验将808nm和980nm两半导体激光迭阵光束通过此技术进行合束, 最终实现更高功率输出,耦合效率70%,光斑大小为3×3mm2,目前国内没有对此项技术进行研究。     

1．55μm超辐射发光管端面减反射膜的研究

减反射膜层折射率和厚度的精密监控是超辐射发光管的关键技术。分析了超辐射发光管端面减反射膜的四种膜系,提出了监控薄膜厚度的挡板调制、高级次过正极值法。采用该法制备超低剩余反射膜的实验表明:单面镀膜后,砷化镓基片的剩余反射率达到0.04%;管芯的反馈谐振被抑制,出现超辐射现象,峰值波长从1610nm移动到1560nm,蓝移约60nm,光谱纹波小于0.3dB。     

二氧化硅钝化膜提高GaN基LED光提取效率的研究

介绍了通过二氧化硅增透膜来提高GaN基LED光提取效率,采用等离子体增强气相沉积法(PECVD)制备了二氧化硅钝化膜,经对器件的测试表明,在器件上沉积二氧化硅增透膜能够使器件的出光效率提高28.4%,同时提高了器件的可靠性。     

Analysis of thermal diffusivity of Ti thin film by thermoreflectance and periodic heating technique

Thermal diffusivity of Ti thin film with several hundred nanometers thickness has been measured by means of thermoreflectance (TR) technique and periodic heating using front heating and front detection configuration. Ti thin films were prepared on Si substrates by dc sputtering method. Then thin Mo layers as reflection layers were coated on Ti thin films. Surface of the Mo layer is irradiated by sinusoidally intensity modulated heating laser. Temperature response at the heated area is measured by a probe laser beam with constant intensity, as a TR signal. Phase lag between the phase of TR signal and that of heating laser beam was obtained from 100 kHz to 2.6 MHz. To analyze thermal diffusivity of Ti thin films using the phase lag data, we developed a three-layer analytical model such as Mo coating (100 nm)∕thin film∕semi-infinite substrate. The calculated phase lag using analytical model is in good agreement with the experimental data for the whole frequency range. The thermal diffusivity of two Ti thin films is determined to be 5 × 10(-6) m(2)∕s, which is 53% of the bulk one.     

A method for preparing cross sections of films on wear surfaces for transmission electron microscopy study

A method for preparing cross sections of surface layers which exist on bulk metal substrates for transmission electron microscopy (TEM) study is described. The surface layer or film is protected by a vacuum-deposited or sputtered coating of a suitable metal. A mask is placed over the surface and non-masked areas are subjected to ion beam etching until the substrate is exposed. A thick electroplated layer is then applied to the surface. This layer adheres well to the ion-etched substrate and seals the coated surface film against damage during the usual slicing and grinding steps which are required for the preparation from bulk materials of thin foils for TEM study. The method was developed specifically for the analysis of boundary and extreme pressure lubrication films on wear surfaces together with the near-surface region of the substrate. However, it is also applicable to the investigation of oxide, corrosion and other surface films.     

Structure analysis of sputter-coated and ion-beam sputter-coated films: a comparative study

Gold, platinum and tungsten films were deposited by low energy input (7 mA, 450 V), or high deposition rate (80 mA, 1500 V), diode sputter coating and by ion beam sputter coating. Film structures on Formvar coated grids and on the surface of coated erythrocytes, resin embedded, sectioned, and recorded at high magnification in a TEM were compared using computer-assisted measurements and analysis of film thickness and grain size. The average grain size of the thinnest gold and platinum films was relatively independent of the mode or rate of deposition but as the film thickness increased, significant differences in grain size and film structure were observed. Thick platinum or gold films deposited by low energy input sputter coating contained large grain size and electron transparent cracks; however, more even films with narrower cracks but larger grain size were produced at high deposition rates. Ion beam sputter coated gold had relatively large grain size in 10 nm thick films, but beyond this thickness the grains coalesced to form a continuous film. Platinum films deposited by ion beam sputter coating were even and free of electron transparent cracks and had a very small grain size (1–2 nm), which was relatively independent of the film thickness. Tungsten deposition either by low energy input or ion beam sputter coating resulted in fine grained even films which were free of electron transparent cracks. Such films remained granular in substructure and had a grain size of about 1 nm which was relatively independent of film thickness. Tungsten films produced at high deposition rates were of poorer quality. We conclude that thick diode sputter coated platinum and gold films are best deposited at high deposition rates provided the specimens are not heat sensitive, the improvement in film structure being more significant than the slight increase in grain size. Thick diode or ion beam sputter coated gold films should be suitable for low resolution SEM, and thin discontinuous gold films for medium resolution SEM. Diode sputter coated platinum should be suitable for medium resolution SEM and ion beam sputter coated platinum for medium and some high resolution SEM. 1–5 nm thick tungsten films, deposited by low energy input or ion beam sputter coating should be suitable for high resolution SEM, particularly where contrast is of less importance than resolution.     

应用SiC反射镜表面改性技术提高TMC光学系统信噪比

为了消除SiC反射镜的固有缺陷,提高反射式光学系统的信噪比,使用SiC表面改性技术对同轴三反射(TMC)光学系统的SiC反射镜进行了处理.首先,应用等离子体辅助沉积(PIAD)技术沉积了一层Si改性层,接着对改性层进行精密抛光,然后在反射镜表面镀制Ag膜和增强膜,最后获得了表面改性对TMC光学系统信噪比的影响.Wyko轮廓仪测试表明,SiC反射镜的粗糙度R_a由10.42 nm降低到了0.95 nm;镀制高反射膜后,主镜、次镜、三镜及折叠镜在0.5～0.8 μm可见光波段的反射率＞98%.计算结果表明,应用了表面改性技术后TMC反射式光学系统的信噪比提高了5%以上,说明SiC表面改性技术是一种提高TMC光学系统信噪比的有效方法.     

高性能偏振膜的研制

综述了国内外科研人员在高性能偏振膜的研制方面开展的工作,主要涉及偏振膜光谱性能、抗激光损伤阈值和膜层应力控制等方面的研究。针对我国神光系列装置对偏振膜的性能要求,简述了中国科学院上海光学精密机械研究所采用电子束沉积技术在光谱性能、损伤阈值和面形精度三个方面开展的研究工作。给出了在薄膜设计、制备和后处理等方面进行的研究和取得的进展。结合上述研究成果,得到了低缺陷密度、低应力的高性能偏振膜。由本科研团队研制的布儒斯特角薄膜偏振器在在2012年和2013年SPIE激光损伤国际会议(SPIE Laser Damage)组织的全球性偏振膜激光损伤阈值水平竞赛中连续取得了p分量损伤阈值和平均损伤阈值最佳的结果。另外,通过解决应力诱导膜层龟裂的重大技术问题,在国内首先推出了大口径偏振片,该大口径偏振片满足透射率TP98%,反射率RS99%的光谱性能要求和17J/cm2(9ns)的通量运行要求,有力支撑了我国SGII-UP大型激光装置的稳定运行。     

光学薄膜技术改善分布反馈(DFB)激光器的光谱特性

报导了利用镀光学薄膜的方法来改变镀层厚度,可以有效地将原来处于双模工作的１．３μｍ ＤＦＢ激光器变为单模工作。模式改变起主导作用的是加镀膜层影响到激光器端面反射特性中的相移。实验表明,镀膜技术可望成为改善ＤＦＢ激光器单模工作的一种辅助方法。实验结果有助于理解相移对激射特性的作用。     

Hall-effect hysteresigraph for amorphous bubble-domain materials

A hysteresigraph is described which provides a much more rapid measurement of the coercivity of amorphous bubble films than any previously used method. This device utilizes the Hall effect to sense the film magnetization and has sufficient sensitivity and stability that coercivities as low as approximately 1 Oe can be readily measured. Although this device cannot provide an absolute measurement of saturation magnetization, approximate values of this quantity can be inferred from the saturation field indicated by the hysteresis loop. A probe-contact arrangement is employed which permits measurements to be made even on films having an insulating passivation layer.