单通激光片状放大器的模拟计算分析

介绍了高功率固体激光驱动器中单通片状放大器 (SSA)的模拟和实验研究结果。对放大器能量传输的各环节进行全系统模拟 ,在能源系统优化的前提下 ,对不同抽运条件和不同抽运腔构型放大器的增益特性进行实验研究 ,2 2kV工作电压下 ,获得了 4 9%cm-1的小信号增益系数和 2 4 3%的储能效率。同时还分析了放大器的抽运热畸变及波前变化 ,实验测量了由抽运引起的腔内洁净度变化情况。     

新型阵列式片状放大器点探针光小信号增益实验研究

介绍了一台通光口径为 2 9cm× 2 9cm的新型高功率固体激光阵列式片状放大器 ,并且在不同充电电压下进行了实验测试。在充电电压为 2 3kV ,抽运能量密度为 10 0J/cm3 的条件下 ,获得了平均值为 4 99%cm-1的小信号增益系数和 3 0 %的储能效率。     

非链式脉冲DF激光器增益分布特性

为了研究非链式脉冲DF激光器的增益分布特性,在考虑谱线碰撞加宽和多普勒加宽对增益系数影响的基础上,运用变耦合率法给出了计算增益系数的简便公式。利用光阑移动扫描采样法,实验测量了不同输出镜透过率条件下DF激光器增益区横截面上各采样点的激光输出功率。对于每个采样点,计算得到两个独立的增益系数,其标准差差小于3%。激光平均增益系数为2.594 3 m-1,非输出损耗系数为1.243 5 m-1。对各采样点的增益系数进行二维插值,结果显示在激光增益区横截面上增益系数呈现中央高、边缘低的超高斯分布。研究成果可为非链式脉冲DF激光器谐振腔和电极结构设计提供依据,并可为该激光器的气体放电均匀性分析提供参考。     

高功率钕玻璃固体激光放大器物理性能优化设计

给出高功率固体激光放大器小信号增益特性的时间和光谱分辨的物理模型,该模型包括了激光放大器能量转换的4个主要环节:(1)抽运源,(2)腔传输,(3)增益介质和(4)增益特性与储能效率.该模型详细地考虑了氙灯辐射的光谱和时间特性,以及增益介质中钕离子的光谱吸收特性.为避免大量的数值运算,从而对不同的放大器构型进行快速的优化判断,模型中采用了经验方法来描述放大器的放大自发辐射效应.利用该物理模型,我们对目前正在研制的口径达300 mm×300 mm高功率钕玻璃固体激光放大器的各单元参数进行了细致的优化,并给出了放大器的增益特性及储能效率,模拟计算结果表明,在23 kV常规工作电压下(氙灯工作负载fx=0.2),放大器小信号增益系数为5.1%cm-1,储能效率为3.1%,满足设计要求.最后我们还利用该模型对几种典型的放大器进行了综合比较,包括单口径片状放大器(SSA)、Beamlet 2×2片状放大器、NIF 4×2片状放大器等.(OC37)     

在压力高达一个大气压的CO_2-He-N_2混合气中余辉增益测量

一个连续波10.6微米的CO_2激光器被用来测量CO_2-He-N_2混合气压高达1个大气压的横向激励电容放电中作为时间函数之小信号增益。测量了放大器增益和平均增益系数。研究了不同的混合气,并观察了N_2和He对于增益的一般作用,随着气压降低增益一直增加,在2.45米的放大器长度上得到大于6的放大系数,随着加到放电电容器上电压的增加,增益也增加。放电所致的激光束的偏离以及气体中声波的产生,均归因于气体的发热。     

神光Ⅱ各级放大器小信号增益的在线测量

神光Ⅱ装置精密化功率平衡要求8路子光束的输出能量平衡和脉冲波形一致，即每条放大链的增益和透过率相同。但装置因日常打靶工作需要，8路子光束放大链中同级放大器的增益能力差异较大。针对该问题，利用一种精度优于1％的小能量测量系统，对神光Ⅱ装置8路四级放大器的小信号增益进行在线测量，分别得到了40，70棒状放大器，100片状放大器和200双层片状放大器在正常工作电压下的小信号增益值，掌握了每路各级放大器的增益特性，精确量化了各路同级放大器的差异，为神光Ⅱ精密化功率平衡调试提供了宝贵的实验数据。     

Fabry-Perot型GaAs-GaAIAS DH激光放大器的增益和频率带宽

本文报导了用实验方法研究Fabry-Perot型GaAs-GaAlAs DH半导体激光放大器的结果。在共振放大条件下测量了总增益G_C及其随注入电流的变化,并通过G_C随入射光频率γ的变化测得频率带宽⊿v_(1/2)。用Hakki-Paoli的方法测量了光放大器的增益系数随注入电流的变化,求得单程增益G_S随注入电流的变化,利用G_S计算了G_C随注入电流的变化及频率带宽⊿v_(1/2)。计算结果和实验值符合较好。     

KrCI准分子激光振荡——放大系统的研究

本文描述了一种结构简单的紫外光预电离放电泵浦的KrCl准分子激光振荡-放大系统。测得放大器单程增益系数为0.03 cm~(-1)。研究了放大器单程增益与光延迟时间的关系。     

百焦耳级有源反射镜钕玻璃激光放大器

搭建了一套氙灯抽运的有源反射镜钕玻璃激光放大器系统。实验研究了有源反射镜钕玻璃激光放大器的增益特性及能量提取。钕玻璃几何尺寸为380mm×160mm×30mm,掺杂浓度为2.2%(质量分数)。充电电压为23kV时,实验测得系统的小信号增益系数为0.056cm-1,储能效率为2.0%。充电电压为22kV时,输出激光光斑尺寸为126mm×126mm,脉冲宽度为5ns;预放注入能量为6.67J时,激光放大系统获得最大为349J的能量输出。系统静态波前峰谷(PV)值为8.38λ。     

宽带平坦L-波段掺Er光纤放大器及其增益提高

利用980nmLD前向泵浦方式,实现了L-波段信号的放大,在1560～1610nm波长范围内,小信号增益平均为11．1dB,增益波动小于1．0dB。利用插入附加泵浦激光提高增益的方法,在保持增益带宽和增益平坦度不变的情况下,分别插入-25dBm的1532和1551nm激光时,放大器的小信号增益平均为11．2dB和12．8dB。     

高频激励横流CO2激光器的实验研究

本文在实验上在气压为120mba、100mba和80mba,气压比为CO2:N2:Ar=7:46.5;46.5,间隙为20mm,26mm和27mm,电极直径为12mm、长为700mm的情况下,对网络的高频传输特性,间隙高频放电的伏安特性及激光功率输出特性进行了一定的研究,在国内首次得到高频激励横流CO2激光器400W的激光输出.注入功率密度达20W/cm3,与相同条件下的直流针板式激光器相比最大注入功率提高了约一倍,最大电光转换效率为9%.     

Bright green organic light-emitting devices having a composite electron transport layer

A bright green organic light-emitting device employing a co-deposited Al-Alq₃ layer has been fabricated. The device structure is glass/indium tin oxide (ITO)/ N, N′-diphenyl-N, N′- (3-methylphenyl)-1, 1′-biphenyl-4, 4′-diamine (TPD)/tris(8-quinolinolato) aluminum (Alq₃)/ Al-Alq₃/Al. In this device, Al-Alq₃ is used as electron transport layer (ETL). The device shows an operation voltage of 6.1 V at 20 mA/cm². At optimal condition, the brightness of a device at 20 mA/cm² is 2195 cd/m² achieved a luminance efficiency of 5.64lm/W. The result proves that the composite Al-Alq₃ layer is suitable for the ETL of organic light-emitting devices (OLEDs).     

Preparation and properties of pbs crystals with low carrier concentrations

By using a two-temperature annealing technique to reduce native defect concentrations we have achieved carrier concentrations as low as 5. 6 x l0¹⁵ cm^-3 in bulk single crystals of PbS. Hall coef-ficient, electrical resistivity, thermoelectric power, infrared absorption coefficient, and CO₂ laser transmission scan measure-ments were carried out for various samples in the carrier con-centration range from 5. 6 x l0¹⁵ cm^-3 to 4. 8 x 10¹⁸ cm^-3. The low-temperature carrier concentration data were analyzed using a quantitative theory for the native defect concentrations as a function of the sulfur vapor pressure. Calculations based on this theory yield good agreement with experiment for intrinsic carrier concentration and defect equilibrium coefficient values of 5.5 x 10¹⁷ cm^-3 and 5. 0 x 10¹⁷ cm^-3, respectively, at 600°C. This work was sponsored by the Department of the Air Force.     

Photorefractive Performance of Hyperstructured Cyclotriphosphazene Molecular Glasses containing Carbazole Moieties

Two hyperstructured photorefractive (PR) molecular glasses ( M1 and M2 ) with a cyclotriphosphazene core are synthesized via nucleophilic substitution and an azo‐coupling reaction. These molecules exhibit excellent solubility in common organic solvents and maintain a complete amorphous state in spite of their high glass‐transition temperature. The nonlinear optical effects, two‐beam coupling and four‐wave mixing, respectively, are used to prove the PR performance in the optically transparent films of M1 and M2 doped with 30 % N‐ethyl‐carbazole. With no external electric field, a gain coefficient of 102 cm^–1 and diffraction efficiency of 24 % are obtained in the composite made from M1 , and an even higher gain coefficient of 214 cm^–1 and diffraction efficiency of 31 % are obtained in the composite made from M2 owing to its higher chromophore loading.     

Efficient Outdiffusion of Hydrogen from Mg-Doped Nitrides by NF<Subscript>3</Subscript> Annealing

High concentration (more than 1 × 10¹⁸ cm⁻³) of hydrogen atoms remaining in Mg-doped GaN epitaxial layers grown by metalorganic chemical vapor deposition even after conventional annealing in N₂ ambient could induce degradation in GaN-based devices containing Mg-doped layers. In this study, by annealing Mg-doped nitrides in NF₃ ambient, we successfully reduced residual hydrogen below mid-10¹⁷ cm⁻³, which is much smaller than by N₂ annealing. NF₃ annealing enhances outdiffusion of hydrogen from the bulk, which is possibly because the nitrogen and fluorine radicals decomposed from NF₃ accelerate desorption of hydrogen adatoms from the surface. The proposed method for Mg activation would improve the reliability of GaN-based light-emitting diodes and laser diodes.     

Heat Dissipation of Transparent Graphene Defoggers

In spite of recent successful demonstrations of flexible and transparent graphene heaters, the underlying heat‐transfer mechanism is not understood due to the complexity of the heating system. Here, graphene/glass defoggers are fabricated and the dynamic response of the temperature as a function of input electrical power is measured. The graphene/glass defoggers reveal shorter response times than Cr/glass defoggers. Furthermore, the saturated temperature of the graphene/glass defoggers is higher than for Cr/glass defoggers at a given input electrical power. The observed dynamic response to temperature is well‐fitted to the power‐balance model. The response time of graphene/glass defogger is shorter by 44% than that of the Cr/glass defogger. The convective heat‐transfer coefficient of graphene is 12.4 × 10^?4 W cm^?2 °C^?1, similar to that of glass (11.1 × 10^?4 W cm^?2 °C^?1) but smaller than that of chromium (17.1 × 10^?4 W cm^?2 °C^?1). The graphene‐based system reveals the lowest convective heat‐transfer coefficient due to its ideal flat surface compared to its counterparts of carbon nanotubes (CNTs) and reduced graphene oxide (RGO)‐based systems.     

In气氛退火对Cd0.9Zn0.1Te材料电阻率的影响研究

在不同温度条件下对Cd0.9Zn0.1Te晶片进行In气氛退火热处理,显著提高了Cd0.9Zn0.1Te材料的电阻率。通过实验测量和理论建模计算,得到了1 073、1 023和973K条件下In原子在Cd0.9Zn0.1Te晶片中的扩散系数分别为4.25×10-9 cm2·s-1、9.02×10-10 cm2·s-1和2.17×10-10 cm2·s-1,并且拟合出了1 073~973K范围内扩散系数和温度之间的函数关系表达式D(T)=2.15×exp(-1.9/k0T)及频率因子D0等数据。最后,对实验结果进行了简要的对比和分析解释。     

Properties of pulsed laser deposited vanadium oxide thin film thermistor

Vanadium oxide thin film has been deposited on glass substrate at room temperature using pulsed laser deposition with the laser fluence of 1.4 J/cm² under high vacuum. X-ray photoelectron spectroscopy analysis shows that the film is oxygen deficient compared to the stoichiometric V₂O₅. X-ray diffraction study reveals the amorphous nature of the film. Atomic force microscopy ensures the particulate free film with smooth surface topography. From the temperature-dependent resistance measurements, thermistor parameters such as temperature coefficient of resistance (α) and thermistor constant (B) were determined as 28000 ppm K⁻¹ and 2623 K, respectively.     

High repetition rate CH4 laser

A 16-μm CF₄ laser oscillator has operated at 1 kHz in a cooled static cell. Pump energies required from the low pressure, Q-switched, cw discharge CO₂ laser were as low as 60 μJ. The laser cavity employed a multiple-pass off-axis path resonator in a ring configuration. CF₄ laser power at 615 cm^?1 and a 1-kHz repetition rate exceeded 300 μW.     

受激布里渊散射的新介质

为了寻找性能良好的受激布里渊散射(SBS)介质,根据SBS对介质的要求,试验了几种全卤代烃新介质。测定或计算了增益系数、声子寿命和吸收系数等参数。四氯乙烯(C2Cl4)具有良好的SBS特性,其增益系数为9.0cm·GW-1,声子寿命为0.59ns,吸收系数为0.003cm-1。分析和讨论了介质化学结构对SBS特性的影响。