一种用于小型激光器的新颖放电结构的放电性质研究

依据微空心阴极自持的辉光放电结构,设计了一款新颖的微小放电结构.用空气进行了有关的放电实验,稳定的直流辉光放电,放电气压最大能够达到66.7 kPa.放电的伏安特性具有正的斜坡,放电能够稳定地运行,而不需要个体镇流电阻.在气压为40 kPa和放电电流为60 mA时,放电等离子体中的电流密度估计为0.048 A/cm2,功率密度估计为52.8 W/cm3,电子密度估计为2.7×1013 cm-3.实验结果表明:这种高气压、大体积、高电子密度的放电等离子体能够用作小型激光器的工作介质.     

介质阻挡无声放电中电子温度和电子能量分布的探极诊断

用对称双探极和非对称双探极分别诊断氖气中介质阻挡无声放电的电子温度和电子能量分布.本文概述其诊断技术的原理、装置和实验结果,并分析讨论了实验结果.实验表明,这种放电的电子温度随着气压的增加而减少,并明显高于相应气压下的直流放电电子温度,而且,其电子能量分布明显偏离Maxwellian能量分布.     

氮化镓基发光二极管的发光光谱和功率特性

用直流和脉冲电流的方法研究了氮化镓基紫色和蓝色发光二极管的发光光谱和功率特性.结果表明,紫色发光二极管的发光中心波长在直流情况下随电流的增加发生红移,在脉冲情况下随电流的增加发生蓝移;蓝色发光二极管的发光中心波长在直流和脉冲情况下都发生蓝移.两种发光二极管的功率在直流情况下会发生饱和,并随电流的进一步增加而急剧减小,以上现象可能是由于热效应和量子阱中的压电效应引起的.     

氮化镓基发光二极管的发光光谱和功率特性

用直流和脉冲电流的方法研究了氮化镓基紫色和蓝色发光二极管的发光光谱和功率特性.结果表明,紫色发光二极管的发光中心波长在直流情况下随电流的增加发生红移,在脉冲情况下随电流的增加发生蓝移;蓝色发光二极管的发光中心波长在直流和脉冲情况下都发生蓝移.两种发光二极管的功率在直流情况下会发生饱和,并随电流的进一步增加而急剧减小,以上现象可能是由于热效应和量子阱中的压电效应引起的.     

氮化镓基发光二极管的发光光谱和功率特性

用直流和脉冲电流的方法研究了氮化镓基紫色和蓝色发光二极管的发光光谱和功率特性.结果表明，紫色发光二极管的发光中心波长在直流情况下随电流的增加发生红移，在脉冲情况下随电流的增加发生蓝移；蓝色发光二极管的发光中心波长在直流和脉冲情况下都发生蓝移.两种发光二极管的功率在直流情况下会发生饱和，并随电流的进一步增加而急剧减小，以上现象可能是由于热效应和量子阱中的压电效应引起的.     

不同气压条件下空气介质阻挡放电的特性

建立了一套放电装置,放电室内的空气压力可调。设计并制作了单面梳状和平行双平面两种电极板,在不同气压环境下进行空气介质阻挡放电实验。拍摄记录了放电现象,采用电荷-电压(q-V)法处理了放电的有关测量数据,对实验结果进行了分析。研究结果表明,空气介质阻挡放电的特性变化与放电环境气压有关。在各种气压条件下,该文的介质阻挡放电均呈脉冲群间歇性;随着放电环境气压减小,放电由常压下的粗大流注电晕逐渐变成细而密集的细丝状微流注电晕,直至融合为貌似辉光放电;放电脉冲群的密度和宽度也随气压降低而增加,但脉冲幅值减小。放电的有功功率随气压变化并非单调增减,当放电气压约为0.04 MPa时,消耗的有功功率最小,常压下和近真空时放电的有功功率都要大得多。     

用光电流效应测量CO_2正柱放电中径向电子密度的分布

利用光电流效应测量了CO_2正柱放电中径向电子密度分布,发现随气压升高和电流增大,电子密度分布向管轴收缩。     

微放电阵列构成的直流平板等离子体显示技术

设计了一种新颖的放电结构,它是由“微空心阴极放电”与“封闭微空心阴极放电”串联,然后并联构成的微放电阵列。它产生的高气压高电流密度辉光放电等离子体能够用来制作平面等离子体显示或光源。利用该放电结构进行了空气直流放电实验,在2.7~66.7kPa的气压范围都能够产生稳定的直流放电。测量了气压p=27kPa时的伏安特性和电流I=9mA时的放电图。测得的伏安特性曲线在整个放电区域都具有正的微分电阻特性。估算的电流密度为63.7A/cm3;功率密度为3.44×103W/cm3;电子密度在1013cm-3量级。实验结果表明该结构能够用于直流平板等离子体显示。     

2千瓦横向流动闭合循环CO_2激光器

本文报导了千瓦级横向流动闭合循环 CO_2激光器的组成,着重讨论了无弧光放电电极结构及放电特性。采用多针触发使较大放电电流时的辉光放电稳定性明显提高;主电源直流输出特性及限流电阻选择对放电稳定性及功率输出影响很大。放电区气流速度40米/秒,工作气压46毫米汞柱,激活区长度86厘米,获得2千瓦连续多模输出,电光效率达15%。     

大气压脉冲CO_2激光器的参量性能

最近已经报导由工作在大气压下脉冲放电的CO_2激光器中获得了兆瓦级峰值功率[A.J.Beaulieu LF.6.14.1970]。放电横跨于激光器,产生了高气压下激励激光器所要求的高电场强度。本文描写在一只沿管轴方向利用了60只独立电容器的1.5米长的激光管中,作为气压和放电电压函数测量了小信号增益,脉冲能量以及脉宽。增益系数每厘米为1％量级或更小些,与典型的直流激励的CO_2激光器的数值相当。峰值功率近似地按总气压的平方而增加,这是由于随着气压的增加使得脉冲能量增加和脉冲宽度减少两者所致。     

Fiber Methane Gas Sensor and Its Application in Methane Outburst Prediction in Coal Mine

Fiber optic methane gas detecting system based on distributed feedback （DFB） laser wavelength scanning technique is demonstrated. Wavelength scan of methane absorption peak at 1665.9 nm is realized by saw tooth modulation of current which is injected to DFB laser. A reference methane gas cell is used to find the methane absorption peak around 1666 nm, and normalization is used to reduce the outside affection such as power drift, fiber loss. Concentration is got by arithmetic processing absorption coefficient of the methane gas. In-situ test is carried out in coal mine and long time precision of 0.05% is achieved. Some spot data of coal mine is introduced. By the system, methane outburst can be measured.     

甲烷红外吸收光谱随环境变化关系研究

基于气体谱线展宽理论,数值模拟了甲烷泛频带2ν3的R(9)支吸收线型。利用可调谐半导体激光器从实验上测量了甲烷2ν3的R(9)支吸收线型。通过扫描1637.6～1637.92 nm甲烷混合气体的吸收光谱,计算得到甲烷自展宽系数(0.0725±0.008)cm-1/atm,空气碰撞加宽系数为(0.0335±0.0012)cm-1/atm。并首次从理论上给出了甲烷1637.8 nm吸收峰中心波长,在标准大气压条件下,随甲烷浓度变化的关系。对提高激光调制技术测量气体精度,具有重要意义。     

Combining TDLAS and multi-fusion algorithms for methane gas concentration detection

High-precision methane gas detection is of great importance in industrial safety, energy production and environmental protection, etc. However, in the existing measurement techniques, the methane gas concentration information is susceptible to noise, which leads to its useful signal being drowned by noise. A fusion algorithm of variational modal decomposition (VMD) and improved wavelet threshold filtering is proposed, which is used in combination with tunable diode laser absorption spectroscopy (TDLAS) to implement a non-contact, high-resolution methane gas concentration detection. The fusion algorithm can perform noise reduction and further segmentation of the methane gas detection signal. And the simulation and experiment verify the effectiveness of the fusion algorithm, and the experimental results show that for the detection of air containing 10 ppm, 30 ppm, 60 ppm, 80 ppm, and 99 ppm methane, the errors are 12.75%, 8.18%, 3.37%, 2.46%, and 1.78%, respectively.     

应用于吸收型甲烷传感器的1650nm DFB激光器的研制

光学吸收法是一种工程上有效可行的检测痕量甲烷气体的方法,具有广泛地应用于构建煤矿坑道等场合的安全防护和报警系统的潜力.为实现针对甲烷气体1653nm吸收峰特性的单色光源,采用金属有机化合物化学气相沉积外延和纳米压印等技术手段,从多量子阱外延材料设计和金属有机化合物化学气相沉生长到器件封装,研制了1653nm分布反馈激光...     

Wavelength references for 1300-nm wavelength-division multiplexing

We have conducted a study of potential wavelength calibration references for use as both moderate-accuracy transfer standards and high-accuracy National Institute of Standards and Technology (NIST) internal references in the 1280-1320-nm wavelength-division-multiplexing region. We found that most atomic and molecular absorption lines in this region are not ideal for use as wavelength references owing to factors such as weak absorption, complex spectra, or special requirements (for example, frequency-doubling or excitation with an additional light or discharge source). We have demonstrated one of the simpler schemes consisting of a tunable diode laser stabilized to a Doppler-broadened methane absorption line. By conducting a beat-note comparison of this reference to a calcium-based optical frequency standard, we measured the methane line center with an expanded uncertainty (2/spl sigma/) of /spl plusmn/2.3 MHz. This methane-stabilized laser now serves as a NIST internal reference.     

Spectroscopic diffusion coefficient of methane at 3.39 micron wavelength by a laser study

A novel differential re-analysis of Hubbert's (1976) laser study data of the 3.39 μm absorption (Dicke-narrowed) of methane shows that the spectroscopic diffusion coefficient is 10% different from the calculated self-diffusion coefficient. More accurate studies above 10 torr pressure are needed.     

甲烷和氢气混合气体中的多波长拉曼转换

探索Nd：YAG倍频激光与受激拉曼散射(SRS)结合获得从紫外到可见光范围的多波长输出，可应用于激光雷达探测空气污染等领域。利用Nd：YAG激光的三倍频355nm波长输出在甲烷及甲烷和氢气混合气体中的拉曼特性进行研究。获得在396nm，416nm，447nm和503nm 515nm等多个波长分别约100mW的同时输出，以及对个别波长的增强。讨论了不同常见的工作气体及混合气体的特点。与单一工作气体(氢气或甲烷)相比，混合气体可以获得更为丰富的波长输出。相比甲烷气体在紫外激光照射下的分解作用，由于氢气的加入一定程度上抑制了分解反应，混合气体产生的分解沉淀较少。     

Tunable Diode Laser Spectroscopy With Wavelength Modulation: A Phasor Decomposition Method for Calibration-Free Measurements of Gas Concentration and Pressure

The principles and implementation of a phasor decomposition method for analyzing signals in tunable diode laser spectroscopy with wavelength modulation are described. This new technique enables recovery of the isolated and normalized residual amplitude modulation (RAM) signal from measured first harmonic signals at any chosen fundamental modulation frequency. Like the previously reported RAM technique, this new approach is absolute, yielding gas absorption line shape functions, concentrations and pressures without the need for calibration, under certain defined operating conditions. It represents an advancement of the RAM technique in that it obviates the need to operate at a specific high frequency to achieve phase quadrature between the RAM and derivative signals: the signals may be recovered at their maximum levels at any frequency. Measurements of the 1650.96 nm and the 1666.2 nm rotation/vibration absorption line shape functions for 1% and 10% methane in nitrogen at various pressures are compared to theoretical predictions derived from HITRAN data. The excellent agreement confirms the validity of the new technique. Further measurements of concentration and pressure confirm the efficacy of the technique for determining concentration in industrial process environments where the pressure may be unknown and changing. With the above features this new method is particularly suited to stand alone instrumentation for on-line deployment in industrial processes where the calibration factors in the conventional approach would present significant difficulties.     

铜激光光脉冲的时间特性

测量了铜激光两种波长510.6nm和578.2nm光脉冲的抽运时间与氖压和充电电压间的关系。波长578.2nm的光脉冲的抽运时间在不同氖压下随电压的增加而缩短。波长510.6nm光脉冲的抽运时间与电压的关系对氖压较为敏感。     

CO2 laser performance with a distributed gold catalyst

The performance of a CO₂ laser was improved by coating the inside wall of the discharge tube with a discontinuous gold film. In the presence of the discharge, the gold acts as an ambient temperature catalyst to reform decomposed CO₂. The gold coated laser delivered 122 W/m for both sealed-off and flowing operation. CO₂ decomposition levels are presented as a function of input power, gas pressure, and temperature. Atomic oxygen, generated by the discharge, appears to be required for gold to exhibit any detectable catalytic activity