选频N_2O激光器

N_2O是线性非对称分子,它的激光工作能级为(001)和(100)振动态以及相联系的转动态,由于下工作能级(100)可以向基态(000)进行偶极跃迁,所以粒子数反转密度较低,加之N_2O气体在高温下容易分解,这些都会使激光功率低于CO_2激光。为了克服这些不利因素,我们采取流动工作气体方式获得连续的激光输出。 激光管长为2100毫米,放电长度为1800毫米,放电管内径20毫米。腔体的一端由NaCl布氏窗封密构成半外腔。金膜全反凹面镜曲率半径为10米,选频用的金属基底光栅为100条/毫米、闪耀波长10.6微米的原刻光栅。激光管装有进气口和出气口,分别与气源钢瓶和抽气泵相联,抽气速率8升/秒,折算管内流速25米/秒。     

CO_2气动激光的增益和功率

本文报导一种CO_2气动激光结构的小信号增益和辐射功率的实验和理论研究,以确定增益和激光功率的最佳气体温度、压力和气体成分。激光器用二种气体混合物(CO_2—N_2—He和CO_2—N_2—H_2O),在温度800～2200°K、压力2～16大气压、以及广泛的气体成分范围条件下运转。此激光器,对增益来说最佳的气体温度大约是1500～1600°K,对功率来说,高于2200°K。发现当He或H_2O的浓度分别低于10％和1％时,气动激光器不振荡。分析了为建立增益的各种动力学过程和决定激光功率的各种激光光腔参数。估计了理论用于确定增益和功率的可能性。在大多数场合,增益理论给出了很好的定量结果,而功率理论仅给出定性的结果,得到的激光功率约2瓩。     

双面预电离N_2激光器

在双层平板电容 Blumlein 系统激发的 N_2激光器中,采用简易的双面预电离方法(四电极激光器)提高了 N_2激光器的输出稳定度与输出功率。     

N_2O分子10μm波段谱线的位移

本文从实验和理论两方面研究了N_2O分子差频带ν_3-ν_1中各不同振转谱线的压力位移。谱线压力位移比谱线半宽度小二至三个量级。用半经典Anderson-Tsao-Curnutte理论计算N_2O分子时,发现对于线性分子的N_2O,其一阶位移为零,人们想当然地认为二阶结果一定比一阶结果小,因此N_2O分子的位移量一直无人研究。事实上N_2O位移量是存在的,它的A.T.C.二阶结果并不为零。根据A.T.C.理论,二阶位移由下式决定:     

一种紫外,可见和红外的简易高功率TEA激光器

我们报导了一种简易、高功率的横向激励大气压激光器.它用 N_2、XeF 及 KrF 在紫外运转,用 F 及 Ar 在可见和近红外运转.用 HF、CO、CO_2及 N_2O 在红外运转。在同一种器件中,从N_2得到峰值功率0.5MW 及脉冲能量4.5mJ,从 XeF 得到1.5MW 及16mJ,从 CO_2得到18MW 及2.7J,由于在激光混合气体中加进 NF_3,N_2激光器的性能大为改善(1MW,10mJ).在接近或超过大气压时取得最大功率与能量.     

N_2O红外光谱性质在气象卫星温度探测中的运用

本文分析了大气中N_2O的红外光谱特性对气象卫星的大气温度探测的影响。N_2O有三个主要吸收带(4.5μm,7.8μm,17μm),气象卫星近地层大气温度探测使用4.5μm谱带。这种探测的物理本质就是探测N_2O气体的温度,由于90km以下大气处于完全混合状态,在局地热平衡假定下,N_2O气体的温度就代表大气温度。卫星测量4.5μm的辐射值的大小主要由N_2O的含量和所在高度的温度决定,假定N_2O的混合比不变,辐射仅随温度变     

20Hz时脉冲能量6mJ的N_2激光器

本文报导在研制电容倒空式N_2激光器中如何提高脉冲能量、平均功率、峰值功率、光束质量和稳定性方面的进展。在我们研制的器件上获得了1Hz时11.5 mJ;20 Hz时6.7 mJ、稳定性±5.5％、脉宽4.5 ns、峰值功率1.5 MW、平均功率122mW的N_2激光输出。     

大尺度区域CO_2和H_2O的激光在线检测技术

CO2和H2O是大气中两种重要的温室气体,对生态系统中CO2和H2O的浓度进行在线监测可用于分析环境及气候变化。选择CO2和H2O的近红外吸收谱线,利用可调谐半导体激光吸收光谱技术结合自动增益调节技术设计了开放式CO2和H2O在线检测仪。在中国科学院禹城综合试验站进行了1238m光程下,20Hz时间分辨率的连续观测实验,结果表明自动增益调节解决了开放光路检测时探测信号幅度大幅变化问题。监测点的CO2浓度具有白天低,夜间高的日变化周期性。与同场地涡度相关系统的LI-7500对比测量,数据一致性较好。该检测技术灵敏度高、响应速度快、免采样,实现了大尺度区域生态系统中CO2和H2O浓度的稳定、连续、在线检测。     

大功率射频板条CO_2激光器电极波导介质膜研究

针对高功率射频板条CO2激光器铜电极表面放电氧化、受射频放电的电子溅射,致使电极表面不光滑,辉光放电不均匀,光波导损耗严重等问题。利用Al2O3波导介质膜具有的反常色散效应、耐高温能力强的特点,采用磁控溅射镀膜技术对激光器电极表面先镀Al,而后阳极氧化获得Al2O3波导介质膜。分析了磁控溅射工艺对膜层结构的影响,测量了镀膜电极对CO2激光的反射率,并进行了放电实验检测。结果表明,溅射功率为250 W时可得到致密的镀膜层结构;厚度6μm的Al2O3薄膜,对波长10.6μm的CO2激光波导反射率最高达75%;电极镀膜后激光器输出功率在占空比为30%时为700 W,占空比为60%时达到了1300 W。     

中低功率双CO_2激光切割机的开发与应用

研究了大功率单CO2激光切割机和小功率双CO2激光切割机的切割原理,分析了在用这两种形式的激光切割机切割非金属材料木质模切板时,激光功率、切割速度与切割深度、切割的缝形缝宽之间的关系。试验结果表明,用中小功率双CO2激光切割机切割非金属木质板材,无论是设备的制造成本、运行成本,还是切割的精度和缝形缝宽,同用大功率单CO2激光头切割机相比有很多优势。     

N2 effect on GaAs etching at 150 mTorr capacitively-coupled Cl2/N2 plasma

The role of N₂ on GaAs etching at 150 mTorr capacitively-coupled Cl₂/N₂ plasma is reported. A catalytic effect of N₂ was found at 20-25% N₂ composition in the Cl₂/N₂ discharges. The peak intensities of the Cl₂/N₂ plasma were monitored with optical emission spectroscopy (OES). Both atomic Cl (725.66 nm) and atomic N (367.05 nm) were detected during the Cl₂/N₂ plasma etching. With the etch rate and OES results, we developed a simple model in order to explain the etch mechanism of GaAs in the high pressure capacitively-coupled Cl₂/N₂ plasma as a function of N₂ ratio. If the plasma chemistry condition became positive ion-deficient at low % N₂ or reactive chlorine-deficient at high % N₂ in the Cl₂/N₂ plasma, the GaAs etch rate is reduced. However, if the plasma had a more balanced ratio of Cl₂/N₂ (i.e. 20-25% N₂) in the plasma, much higher etch rates (up to 150 nm/min) than that in pure Cl₂ (50 nm/min) were produced due to synergetic effect of neutral chlorine adsorption and reaction, and positive ion bombardment. Pure Cl₂ etching produced 14 nm of RMS surface roughness of GaAs. Introduction of ?20% N₂ gas in Cl₂/N₂ discharges significantly reduced the surface roughness to 2-4 nm. SEM photos showed that the morphology of photoresist mask was strongly degraded. Etch rate of GaAs slightly increased from 10 to 40 nm/min when RIE chuck power changed from 10 to 150 W at 12 sccm Cl₂/8 sccm N₂ plasma condition. The surface roughness of GaAs etched at 12 sccm Cl₂/8 sccm N₂ plasma was 2-3 nm.     

Scaling of laser power with N2 partial pressure in aconvective-cooled CW CO2 laser

Diffusion-cooled and convective-cooled CW CO₂ lasers have significantly different N₂ partial pressure in their optimum laser gas mixture. While in diffusion-cooled lasers the N₂ fractional concentration is normally within 20% of the total gas pressure, it ranges up to 60% in convective-cooled lasers. By considering various effects of N₂ and solving a simplified rate-equation model analytically, the large difference in the optimum N ₂ concentrations in these two types of CO₂ laser is explained     

Studies of CW lasing action in CO2-CO,N2O-CO, CO2-H2O, and N2O-H2O mixtures pumped by blackbody radiation

A proof of principle experiment to evaluate the efficacy of CO and H₂O in increasing the power output for N₂O and CO ₂ lasing mixtures has been conducted and theoretically analyzed for a blackbody radiation-pumped laser. The results for N₂ O-CO, CO₂-CO, N₂O-H₂O and CO₂-H₂O mixtures are presented. Additions of CO to the N₂O lasant increased power up to 28% for N₂O laser mixtures, whereas additions of CO to the CO₂ lasant, and the addition of H₂O to both the CO₂ and N₂O lasants, resulted in decreased output power     

Role of N2 during chemical dry etching of silicon oxide layers using NF3/N2/Ar remote plasmas

In this work, the role of N₂ gas during the chemical dry etching of silicon oxide layers in NF₃/N₂/Ar remote plasmas was investigated by analyzing the species in the plasma, the reaction by-products in the exhaust, and the chemical properties of the etched surface. Increasing the N₂ gas flow rate resulted in an initial increase in the oxide etch rate up to a maximum value, followed by a subsequent decrease. The increased etch rate of the silicon oxide layers was not ascribed to the increased surface arrival rate of fluorine, but to the enhanced oxygen removal from the silicon oxide caused by the formation of NO₂ molecules. Presumably, the NO radicals formed from the added N₂ gas react chemically with the oxygen in the oxide, leading to the breaking of the Si-O bonds and the effective removal of oxygen, which in turn enhances the formation of SiF₄ resulting in an increased etch rate.     

CO_2波导激光器的最佳化

计算了内腔封离型CO_2波导激光器的EH_11波导模的传输和耦合损耗,设计并制造了内腔封离型CO_2波导激光器.器件的最高输出功率为3.57W,单位激活长度和体积的输出功率分别为0.27W/cm、17.3W/cm~3.     

混合型TEA CO2激光器

本文给出了一种获得单纵模脉冲激光的装置。该激光器由TEA CO2和CWCO2激光器组成,采用内注入,结构简单易注入成功。本实验得到了预期的结果,并提出了进一步改进的方法。     

Rf-excited All-metal CO2 Laser

本文描述了一个紧凑的封离型,RF激励全金属CO     

封离型CO_2波导激光器

本文报导密封CO_2波导激光器的结构设计、制造及其性能.器件放电长为12.5厘米,由四块BeO陶瓷板贴成1.5毫米方孔而成,腔长为15厘米.最大输出功率1瓦,在150托气压下,用两只波导激光器进行光外差测量,测得在一条谱线上(P_(20))调谐宽度为500兆赫.     

Subnanosecond multi-gigawatt CO2 laser

A semiconductor switching technique has been utilized to produce 30-300 ps variable duration CO₂ laser pulses of 0.5-MW peak power. Eight passes through a 1.2-m long, UV-preionized, 3-atm TE CO₂ amplifier raise the output laser peak power to the 10¹⁰ W level. Sampling the amplifier gain in linear and saturated regimes using CO₂ laser radiation ranging from CW to 30 ps pulse length permits comparison with computer modeling of picosecond CO₂ pulse amplification. The potential for further peak power scaling of picosecond molecular lasers is discussed     

Low-pressure H2/N2 annealing on indium tin oxide film

Annealing of indium tin oxide (ITO) film in low-pressure H₂/N₂ was investigated. On carefully selecting the annealing process window, apparent electrical property improvement as well as good optical property can be obtained. It was found that ITO annealed with 2 Pa, H₂/N₂:6/6 sccm, at 500 °C for an hour can increase its electrical conductivity 60% more than ITO without annealing, 58% more than ITO annealed with pure H₂. An annealed ITO without specially selected recipe can easily possess worse electrical and optical properties than that without annealing. It can be explained that annealing ITO in a hydrogen-contained environment can lead to hydrogen reduction–oxygen vacancy playing a donor role in ITO; however, annealing also provides the energy to remove ITO material defects including donors.