532 nm连续激光对砷化镓材料损伤的研究

利用532 nm连续激光对掺Si的n型砷化镓材料进行作用,材料的晶轴方向为〈100〉偏〈111A〉方向15°.实验观察到,连续激光与材料相互作用过程中,材料作用表面的反射光在观察屏上形成环状结构,认为是由夫琅和费衍射产生的,并首次提出将衍射作为探测材料损伤的方法.实验测得砷化镓的阈值损伤功率密度为2.56×105W/cm2.利用温度场的热传导方程计算获得材料的损伤阈值时间与入射光功率密度的关系曲线,并与实验曲线进行了比较.     

脉冲激光加工吸收现象研究

本文深入分析研究激光加工中的吸收现象，提出激光加工中的吸收能量球缺分布设想，并建立其数学模型。通过相应的数据采集装置及分析软件，进行实验论证。结果表明该设想及其数学模型是符合实际的，从而为今后进一步研究激光与材料相互作用机理、提高激光加工精度和质量打下了良好的理论基础。     

大白鼠体内照射治疗白细胞减少症

为了研究砷化镓激光光纤引入机体后对骨髓产生的影响,我们将砷化镓激光光纤直接引入大白鼠体内照射,连续观察了对大白鼠白细胞减少症的治疗作用。现将研究概况介绍如下。 一、材料与方法 1.仪器:使用重庆大学激光光纤科研小组自行装配的XLL型半导体砷化镓激光光纤治疗仪。砷化镓激光以0.5～1.5m长的光纤耦合后插入动物体深部组织。光纤输出端的光功率为1.0～1.3mW,     

激光量热法测量深紫外氟化物薄膜吸收

为了获得薄膜材料吸收率与深紫外激光照射能量密度间的对应关系,掌握薄膜材料深紫外吸收特性,应制定相应的吸收测量规范。介绍了激光量热法的原理及测试流程,分析了测试过程中的剂量效应、非线性吸收和不可恢复吸收等现象,提出了利用激光量热法测量应用于波长193nm紫外光刻系统的氟化物薄膜材料吸收率的方法,并进行了实际测量。根据所建立的测量方法,获得熔石英基底材料在193nm紫外光照射下的剂量效应及出现不可恢复吸收现象时相应的激光能量密度,进而测量出基底材料吸收率与激光能量密度之间的关系;通过热蒸发对基底镀氟化镁及氟化镧单层膜,测量镀膜后样品的吸收率与激光能量密度的关系,通过与镀膜前吸收率的对比,计算了两种薄膜材料吸收率与激光能量密度的关系,推算出薄膜材料在实际工作状态时的吸收率,并得到不同沉积温度下氟化镧薄膜材料吸收率、粗糙度与波纹度。实验结果证实了新提出测量方法的可行性,测量结果为改善系统成像质量以及延长元件使用寿命提供支持。     

连续激光对太阳能电池辐照效应的波段性研究

为了研究太阳能电池在连续激光辐照下的波段性效应,使用位于波段内外的3种波长连续激光对单晶硅太阳能电池的辐照效应和损伤效应进行了实验研究,采用观察电池对激光的响应,对比电池的损伤形貌和太阳能电池组成材料的吸收曲线差异的方法,得到了太阳能电池对本征吸收长波限附近波长激光的吸收机制,分析了10.6μm激光和1064nm激光对...     

空战激光模拟器眼效应实验

空中激光射击模拟实战训练演习,为激光技术在空军中重要应用之一。但需对激光模拟器进行眼效应实验,观察激光发射头输出端是否对眼有损伤作用,以确保飞行人员和地面部队人员的安全。一、激光模拟器的主要性能及剂量测量仪器激光模拟器采用砷化镓半导体激光器,工作物质为砷化镓,发射0.900μm 波长的近红外激光,脉宽400ns,脉冲重复频率10kHz,激光发射头输出口直径为22mm。     

Yb3+掺杂硅酸盐激光玻璃的制备及其特性研究

为了制备Yb3+掺杂硅酸盐激光玻璃,并对其激光特性进行分析,采用富氧气氛下的非化学气相沉积高温熔融工艺,通过Fuchbauer-Ladenburger方法,进行了理论分析和实验验证,取得了所制备硅酸盐激光玻璃的吸收光谱和荧光光谱数据。结果表明,在850nm～1100nm近红外波段为吸收区域,有一宽带吸收峰;吸收主峰位于978nm,次峰位于919nm;其荧光主峰位于1018nm,次峰位于970nm,并理论计算了Yb3+的吸收截面面积、受激发射截面面积及其荧光寿命等特征参量。这一结果对硅酸盐激光玻璃的特性分析是有帮助的,所制备的玻璃材料能够满足激光玻璃的使用要求。     

激光传能协同信号传输下的太阳能电池性能测试

激光无线能量传输在为远距离设备供能方面有着潜在的应用前景,在激光无线传能的同时进行激光无线通讯,具有重要的应用价值。针对砷化镓太阳能电池,对激光传能系统在无线能量传输时激光无线通讯性能进行了测试。实验采用波长808 nm激光实现砷化镓太阳能电池的能量传输,采用波长650 nm激光作为信号的传输,分别对单能量传输、单信号传输以及能量和信号同步传输三种情况下的砷化镓太阳能电池的输出特性进行了测试。结果表明:当单能量传输时,太阳能电池的性能与激光功率密度的大小密切相关,激光功率密度在54.9~90 mW/cm2范围内光电转换效率最大值为46.6%;当单信号传输时,通过测量系统的频率响应得到砷化镓太阳能电池的3 dB带宽约为3.7 kHz,并通过设计放大电路提高系统的通信性能,优化输出波形,使得系统的通信速率从10 kbps提升至240 kbps,输出电压峰峰值达到7.2 V。最后实验测量了不同激光强度下可实现的通信速率,当激光功率密度为59.5 mW/cm2时可实现140 kbps的通信速率,使得激光充电系统在无线能量传输下可以进行信号的传输。     

砷化镓、锑化铟中痕量碲的无火焰原子吸收分光光度法测定

本工作系统地探索了各种腐蚀剂对砷化镓及锑化铟的腐蚀速度,建立了无火焰原子吸收法直接测定砷化镓体材料、砷化镓和锑化铟外延层中的碲.方法准确、快速,满足于材料工艺的要求.     

碲化镉调制器有助于激光宇宙通讯

最近,美帝休斯公司用碲化镉进行了实验,使激光用于宇宙通讯更向现实性靠近了一步。碲化镉的电光特性约为目前广泛用来调制红外激光器的砷化镓的两倍,而光吸收仅为其一半。这样可以减小调制器激励器的体积和重量,这对于航空和宇宙通讯有特殊意义。     

Etching behavior of GaAs/AlGaAs multilayer structure during laser beam scanning

The thermochemical etching behavior of GaAs/AlGaAs multilayer structure during laser beam scanning has been studied. The etch rate changes between GaAs and AlGaAs epilayers as the etching process proceeds through the layered sample. The phenomenon can be explained by the difference of thermal parameters of the heterojunction interface. The local temperature rise from laser irradiation has been calculated to investigate etching characteristics for GaAs and AlGaAs. It is concluded that the good thermal confinement at GaAs/AlGaAs interface produces the wider etch width of GaAs layer than that of AlGaAs layer in GaAs/AlGaAs multilayer. The maximum etch rate of the GaAs/AlGaAs multilayer was 32.5 μm/sec and the maximum etched width ratio of GaAs to AlGaAs was 1.7.     

激光二极管抽运的被动调Q Nd∶GdVO_4激光器

利用激光二极管作为抽运源,分别用Cr4+∶YAG,GaAs和染料片作为饱和吸收体,研究了Nd∶GdVO4激光器的被动调Q特性。Nd∶GdVO4晶体尺寸为4mm×4mm×6mm,掺Nd浓度为1%。利用小信号透过率分别为91%和95%的Cr4+∶YAG,调Q的阈值分别为063W和057W;在抽运功率为369W时,分别得到了脉宽为64ns,80ns,脉冲能量为366μJ,341μJ,重复率为325kHz,378kHz的稳定调Q脉冲。利用580μm厚的GaAs调Q的阈值为039W,在抽运功率为369W时,得到了脉宽为78ns,脉冲能量为215μJ,重复率为366kHz的稳定调Q脉冲。利用初始透过率为70%的染料片调Q获得的脉冲最窄,但是其插入损耗大,抽运阈值高,输出也不稳定。     

GaAs双光子诱导光吸收对调Q激光器脉冲的影响

研究了利用GaAs的双光子诱导吸收实现调Q激光脉冲展宽的原理,分析了GaAs的光吸收特性,建立了激光器速率方程并给出了数值解。在实验上,将GaAs薄片放入一电光调QNdYAG激光器谐振腔中,同理论预测一样,激光输出脉冲的能量、峰值功率都低于常规调Q激光脉冲,同时脉冲宽度得到了展宽。     

GaAs和GaAs/AlGaAs多层量子阱中载流子的超快动力学(英文)

The ultrafast photoexcited carrier dynamics in bulk GaAs and GaAs/ AlGaAs multiple quantum well(MQW)structure has been studied using femtosecond laser pulse pump-probe techniques on the samples grown by MBE. A hot carrier cooling time of 1.5ps in MQW is measured at room temperature. Also, optical phonon emission at 33meV is observed in this sample. These results are found to be similar to that observed in bulk GaAs. A comparison of the hot carrier cooling rates for the two cases suggests that the infra-sub-band optical phonon scattering in MQW may play a dominant role in the cooling of highly excited hot carriers for the narrow wells. The experimental results agree well with that predicted by a simple infinite depth square-well model.     

激光辐照单结砷化镓光伏电池的输出特性

选取单结砷化镓光伏电池和工作波长为808 nm的半导体激光器,开展激光无线能量传输的研究,实验测试了光伏电池性能参数与激光功率和电池温度的关系。结果表明,光伏电池效率随激光功率的增大呈单峰曲线,激光平均功率密度为67.5 mW/cm2时效率最大为49.7%。温度升高,开路电压线性下降,从而导致效率线性降低。激光功率越大,开路电压和效率的温度系数越小。     

Formation of ohmic contacts on semi-insulating GaAs by laser deposition of In

A method for producing ohmic contacts on semi-insulating GaAs by laser ablation with subsequent laser deposition of In is proposed. The contacts are formed at room temperature; thus, the high-temperature annealing used in other technologies is excluded. The ohmic properties of the contacts are retained in a range of currents that is several orders of magnitude wide, regardless of the direction of current. The electric potential is distributed linearly along the sample, and the current is limited only by the bulk resistivity of the material itself. The method is promising for the formation of high-precision arrays of ohmic contacts that penetrate the whole thickness of the sample in the fabrication of microelectronic devices.     

国外长波红外焦平面列阵现状

文中介绍了长波工外焦平面列阵的国外进展，这些列阵包括碲镉汞光电二极管、肖特基势垒器件、砷化镓／砷铝镓多量子阱光导体、高温超导体以及室温工作的焦平面列阵，其中非制冷的混合式热释电陶瓷和单片式的微型测辐射热计焦平面列阵已进入批理生产阶段。     

C-band emission from GaInNAsSb VCSEL on GaAs

The 1.55 /spl mu/m pulsed operation of an optically-pumped GaInNAsSb vertical-cavity surface-emitting laser (VCSEL) is reported. The structure employs a dielectric (SiO/sub 2//TiO/sub 2/) top mirror, while the bottom mirror and active region were grown on GaAs by MBE. Temperature-dependent (10-40/spl deg/C) laser measurements were made for an as-grown sample and an annealed sample, both having a room-temperature lasing wavelength of 1547 nm. Results indicate an annealing-induced blue-shift of the gain peak     

Local indentation modulus characterization via two contact resonance frequencies atomic force acoustic microscopy

Atomic force acoustic microscopy is a dynamical AFM-based technique developed for non-destructive characterization of elastic properties of materials at micrometrical and sub-micrometrical scale. A standard AFM apparatus is equipped with a piezoelectric transducer exciting longitudinal oscillations at ultrasonic frequencies in the sample under investigation. Tip-sample contact stiffness is obtained through the values of the measured resonance frequencies of the cantilever contacting the sample surface, thus allowing one to obtain the value of the sample indentation modulus. The paper describes a generalization of the technique: while performing topography, the first and the second contact resonance frequencies are acquired at each point of the scanned area. Data are then properly processed and acoustic images are obtained as a bi-dimensional pattern of the indentation modulus over the imaged samples area. The technique is illustrated in two different kinds of sample: a metallographic (1 1 0) GaAs sample, prepared by incorporating GaAs single crystals into an epoxy matrix, and a diamond-like carbon film, deposited on a Mo substrate by laser ablation from a glassy carbon target.     

内腔倍频被动调QNd∶YVO_4/KTP激光特性的研究

实现了激光二极管(LD)抽运Nd∶YVO4/KTP,GaAs饱和吸收体被动调Q绿激光运转。测量了GaAs不同 厚度情况下的脉冲重复率、脉冲宽度、单脉冲能量及峰值功率随抽运功率的变化关系。在抽运功率3.22W下,300 μm厚的GaAs获得了381kHz的高重复率,53.2ns的脉冲宽度,0.18μJ的单脉冲能量。通过求解内腔倍频GaAs 调Q工作原理的耦合波方程组,所得的理论值与实验结果相符。