Measurement of neutral gas temperature in inductively coupled plasmas

Dependence of the neutral gas temperature on the gas pressure and discharge power in an inductively coupled plasma source has been investigated using optical emission spectroscopy. Both nitrogen and argon plasmas have been studied separately. In the case of argon plasma, about 5% nitrogen was added to the total gas flow as an actinometer. The maximum temperature was found to be as high as 1850 K at 1 Torr working pressure and 600 W radiofrequency power. The temperature increases almost linearly with the logarithm of the gas pressure, but changes only slightly with the discharge power in the range of 100–600 W. In a nitrogen plasma, a sudden increase in the neutral gas temperature occurs when the gas pressure is increased at a given discharge power. This suggests a discharge-mode transition from the H-mode (high plasma density) to the E-mode (low plasma density). In the H-mode, the gas temperature is proportional to the logarithm of the gas pressure, as in the argon plasma. However, the gas temperature increases almost linearly with the discharge power, which is in contrast to the case of argon plasma. The electron density in the nitrogen plasma is about 10% of that in the argon plasma. This may explain the observation that the nitrogen neutral temperature is always lower than the argon neutral temperature under the same discharge power and gas pressure.     

Modulation instability in silicon optical waveguide considering linear loss

Taking into account the linear loss of silicon-on-insulator (SOI) waveguide, modulation instability (MI) induced by combined effects of self-phase modulation and waveguide dispersions is investigated. The impacts of various parameters to gain spectra of MI are analyzed theoretically, and direct numerical simulation of nonlinear Schroedinger equation is performed as well. Results show that strong MI takes place even in the existence of low light power. The linear loss of waveguide obviously impacts gain spectra of MI, even within ultra-short propagation distance. The peak gain frequency and bandwidth of gain spectra decrease to 41.683% and 41.6879% of their maximum at propagation distance z = 5 mm, respectively.     

Design of Broadband L-band Erbium Doped Fiber Amplifier

An 80 nm bandwidth long wavelength erbium-doped fiber amplifier using a seed light injection method is designed.It is shown that when the wavelength of the seed beam varies from 1520 nm to 1570 nm,the gain at 1610 nm increases and reaches maximum near 1553 nm and then decreases.The gain increases with the seed light power.With the seed light ,the long wavelength Erbium-doped fiber amplifier has 80 nm bandwidth (1570～1650 nm),30 dB gain and noise figure less than 5.0 dB.     

Design of Broadband L-band Erbium Doped Fiber Amplifier

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电激励O2（a1Δg）发生器的实验研究

 在纯氧，及氧气和氩气的混合气体情况下，对射频放电产生O₂（a¹Δg）进行了实验研究。射频频率为13.56MHz，额定功率500W，放电压力133.0~399.0Pa， 氧气流量最大为1.4mmol/s， 氩气流量为2.1mmol/s。研究了O₂（a¹Δg）产率随气体流量、放电气压以及混合气体放电条件的变化。O₂（a¹Δg）产率最大值约为17.5%。     

Power Absorption in High Power Microwave Discharges

Measurements on RF power absorption in microwave discharges at 2.45 GHz, at pressures from 1 to 30 Torr in N2 and from 1 to 500 Torr in Ar, are described. A linear slow-wave structure of the strapped-bar type was employed for coupling RF energy to the plasma. From measurements on the plasma volume and on the total power absorbed, the variation with gas pressure of the RF power density in the plasma was obtained. For an incident power of 1 kW, power densities as high as 2-3 W/cm3 over relatively large plasma volumes could be achieved. The experimental data were used to calculate the pressure dependence of the electron density in an argon plasma, for an incident power of 1 kW.     

Measurements of argon metastable density using the tunable diode laser absorption spectroscopy in Ar and Ar/O_2

Densities of Ar metastable states 1s_5 and 1s_3 are measured by using the tunable diode laser absorption spectroscopy(TDLAS) in Ar and Ar/O2 mixture dual-frequency capacitively coupled plasma(DF-CCP). We investigate the effects of high-frequency(HF, 60 MHz) power, low-frequency(LF, 2 MHz) power, and working pressure on the density of Ar metastable states for three different gas components(0%, 5%, and 10% oxygen mixed in argon). The dependence of Ar metastable state density on the oxygen content is also studied at different working pressures. It is found that densities of Ar metastable states in discharges with different gas components exhibit different behaviors as HF power increases. With the increase of HF power, the metastable density increases rapidly at the initial stage, and then tends to be saturated at a higher HF power. With a small fraction(5% or 10%) of oxygen added in argon plasma, a similar change of the Ar metastable density with HF power can be observed, but the metastable density is saturated at a higher HF power than in the pure argon discharge. In the DF-CCP, the metastable density is found to be higher than in a single frequency discharge, and has weak dependence on LF power. As working pressure increases, the metastable state density first increases and then decreases,and the pressure value, at which the density maximum occurs, decreases with oxygen content increasing. Besides, adding a small fraction of oxygen into argon plasma will significantly dwindle the metastable state density as a result of quenching loss by oxygen molecules.     

Absorption transition of He-Ne laser in Plasma generated by microwave

Plasma luminescence has been measured in the visible range from 200 to 800 nm. The effect of collisions with sputtered copper ionic species at different argon gas pressures on the emission light intensity has been studied. The behaviour of well resolved lines at 210 and 657 nm as a function of gas pressure and microwave radiation power is measured. The transmission of He-Ne laser line (632.8 nm) through the induced plasma shows dependence on the microwave radiation power. There are observed transitions for the absorption of laser intensity for the filling gas pressures 0 and 5.3 torr at the radiation power of 175 W.     

Modulation instability in lossy silicon optical waveguide

Taking into account the small linear loss of silicon-on-insulator(SOI) waveguide, conditions and gain spectra of modulation instability(MI) induced by combined effects of self-phase modulation and waveguide dispersions are investigated. The impacts of various parameters to gain spectra of MI are analyzed theoretically. Results show that strong MI takes place even in the existence of low light power. The MI peak gain is 2 to 3 orders of magnitude larger than that achieved in optical fibers with the same light power. The linear loss of waveguide impacts gain spectra of MI, even within ultra-short propagation distance. The peak gain, peak gain frequency and bandwidth of gain spectra decrease to 66.828%, 41.683% and 41.6879% of their maxima at propagation distance z = 5mm, respectively.     

射频磁控溅射法制备ZnO薄膜的发光特性

利用射频磁控溅射法在硅衬底上制备出具有（002）择优取向的氧化锌薄膜，用波长为300nm的光激发，观察到在446nm处有一强的光致发光峰，它来自于氧空位浅施主能级上的电子到价带上的跃迁。并讨论了发光峰与氧压的关系以及退火对它的影响，且给出了解释。     

Efficient light source based on an inductive ferrite-free discharge at frequencies of 300–3000 kHz

Glass cylindrical tubes from 30 to 50 cm long and from 5 to 7 cm in diameter are used to initiate an inductive discharge in electrodeless luminescent lamps at frequencies of 300–3000 kHz with a power of 50–300 W. The tubes are filled with mercury vapor and an inert gas (argon at a pressure of 0.1 mm Hg), and their inner surface is covered by a phosphor and protective coating. An induction coil (from 5 to 14 turns) made of a low-resistivity multiple-conductor cable embraces the discharge tube in the longitudinal direction, forming a discharge-initiating loop. Because of a high Q factor of the coil, Q _c = 400, the power losses in it are 4–5 W at frequencies higher than 400 kHz; the energy efficiency of the lamp is η = 0.95–0.96. Luminous efficiency ? of the lamp grows with discharge excitation frequency, reaching ? = 83–84 lm/W at a frequency of 530 kHz and a power of 150 W.     

DC magnetron sputtered tungsten: W film properties and electrical properties of W/Si Schottky diodes

Deposition of metallic tungsten (W) thin films on silicon substrates has been carried out using dc magnetron sputtering in argon or xenon gas. The deposition of W films was investigated at various working gas pressures, while the entire deposited W films were obtained at fixed power. The stress, resistivity, and structure of the W films were systematically determined as a function of the pressure of both argon and xenon. A compressive-to-tensile stress transition is observed as the working gas pressure is increased. The transition occurs at a critical pressure and coincides with a significant decrease of the grain size and an increase of the W-film resistivity. The stress transition of W-sputtered films with argon is associated with the transformation of -W phase into -W phase. The films deposited in xenon always exhibit the -W structure. In addition, a change in the Schottky barrier height (SBH) on n-type silicon of about 40±10 meV is observed at the critical pressure. On the other hand, the barrier height on the p-type silicon remains constant under all the experimental conditions investigated. These last results indicate that the Fermi level at the interface is pinned with respect to the valence band edge. The observed variation of the barrier height on n-type Si is discussed in terms of defects, change of the work function of the metal (W), and modification of the band gap of Si. PACS 72.20.-i; 73.30.+y; 73.20.-m     

氩气压力对螺旋波放电影响的发射光谱诊断及仿真研究

螺旋波等离子体源以其高电离效率与高密度优势受到多个领域的青睐。螺旋波放电高电离效率的机理或者功率耦合模式,一直是困扰该领域学者的难点之一,对于放电过程与特性的诊断则是揭示其物理机制的重要途径。光谱诊断能够克服介入式诊断手段对等离子体的干扰同时受等离子体烧蚀等弊端,且响应速度快、操作灵活。为研究螺旋波等离子体的放电特性以及气体压力的影响,开展了以氩气为工质气体的光谱实验研究,并针对实验开展了Helic程序数值模拟。通过改变光纤探头焦距调整径向诊断位置,得到谱线强度的径向分布。由氩原子4p-4s能级跃迁产生的谱线主要集中在740～920 nm区间,谱线相对强度较离子激发谱线较强。实验研究发现,在较低氩气压力范围（0.2 Pa<P_Ar<1.0 Pa）,随着压力增加,放电光强迅速增加,但是当压力增加到大于1.0 Pa之后,光强增长的趋势变缓,甚至部分谱线的相对强度不再增长,达到类饱和状态,朗缪尔探针测量得到离子密度变化趋势与其相似。光强分布在靠近径向边界处（r≈4 cm）存在凸起,且随压力增加,该凸起分布更为明显。通过对电子温度的计算发现,压力增加到一定程度将影响放电均匀性。仿真结果显示,增大压力,功率沉积密度的径向分布逐渐向径向边界处积累,与实验观察到的谱线强度径向凸起相一致,螺旋波与TG波的耦合效率增加。随着气体压力的增加,E_r的径向边界峰值降低,原因是波所受阻尼增强,TG波被有效地局限于径向较窄的边界处。电流密度轴向分量J_z在等离子体内部和边界处的峰值呈显著的减小趋势,可见,虽然压力增加一定程度上提高了等离子体密度,但却相应的减小了电离率,导致轴向电流密度受限。但是径向电流密度J_r却呈现先减小后增大的趋势,且增长幅度明显,综合来看,放电效率有所提高。可见适当增加气体压力,有助于提高放电的功率耦合效率和强度,增加等离子体密度。光强比值法是针对线性谱线参数计算的典型方法,Helic程序亦是专业领域内认可度很高的计算工具,结果可靠,分析方法具有可借鉴性。实验及仿真结果对于提高氩气工质下的螺旋波放电强度提供了一定的参考价值。     

Continuous-wave operation of a room-temperature Ho:YAP laser pumped by a Tm:YAP laser

We reported the Ho:YAP laser pumped by the Tm:YAP laser. The Ho:YAP laser maximum output power was 4.91 W when the incident power was 10.1 W with the threshold of 2.63 W. The slope efficiency was 63.7%, corresponding to an optical-to-optical efficiency of 48.6%. The Ho:YAP output wavelength was centered at 2118.2 nm with bandwidth of about 1 nm. We estimate the beam quality to be M² = 1.29.     

Plasma characteristics and broadband electromagnetic wave absorption in argon and helium capacitively coupled plasma

A one-dimensional self-consistent calculation model of capacitively coupled plasma(CCP) discharge and electromagnetic wave propagation is developed to solve the plasma characteristics and electromagnetic wave transmission attenuation.Numerical simulation results show that the peak electron number density of argon is about 12 times higher than that of helium, and that the electron number density increases with the augment of pressure, radio frequency(RF) power, and RF frequency. However, the electron number density first increases and then decreases as the discharge gap increases. The transmission attenuation of electromagnetic wave in argon discharge plasma is 8.5-d B higher than that of helium. At the same time, the transmission attenuation increases with the augment of the RF power and RF frequency, but it does not increase or decrease monotonically with the increase of gas pressure and discharge gap. The electromagnetic wave absorption frequency band of the argon discharge plasma under the optimal parameters in this paper can reach the Ku band. It is concluded that the argon CCP discharge under the optimal discharge parameters has great potential applications in plasma stealth.     

A Microfabricated Inductively Coupled Plasma Excitation Source

A novel miniaturization of inductively coupled plasma （ICP） source based on printed circuit produced using micro-fabrication techniques is presented. The basic parameters of the novel ICP, including its radio frequency, power loss, size, and argon consumption are less than 1% of that for the case of atmospheric pressure ICP source. For example, at 100 Pa of argon gas pressure, the present ICP source can be ignited by using the rf power less than 3.5 W. Potential applications of the ICP is discussed.     

沿面放电中的辉光和赝辉光放电

利用沿面放电发生器装置，在流动氩气中实现了大气压辉光放电。放电电流波形表现为外加电压每半周期只有一个电流脉冲。驱动电压频率是60kHz时，放电电流脉冲持续时间大于1微秒。氩气中的辉光放电，功率消耗随着外加电压增加或者是气压减小而增大，这种关系可以用汤生击穿理论定性解释。与此对比，大气压空气中的放电电流波形为外加电压每半周期放电为许多脉冲，每个电流脉冲为高频阻尼振荡，这就是赝辉光放电。大气压空气中的赝辉光放电可能是由于气体的流光击穿造成的。     

Discharge-driven electric oxygen-iodine laser superlinear enhancement via increasing g0L

The authors report the development of an electric oxygen-iodine laser with higher output using a larger product of gain and gain length, g0L. A factor of 4.4 increase in laser power output on the 1315 nm atomic iodine transition was achieved with a factor of 3 increase in gain length. I(2P1/2) is pumped using energy transferred from O2(a1Δ) produced by flowing a gas mixture of O2-He-NO through three coaxial geometry radio-frequency discharges. Continuous wave (CW) average total laser power of 481 W was extracted with g0L=0.042.     

高功率全光纤结构主振荡功率放大器中模式不稳定现象的实验研究

模式不稳定指高功率光纤激光随着输出功率提升发生的模式突变,会导致光束质量下降,限制了衍射极限光束质量光纤激光输出功率的提升,本文研究了全光纤结构主振荡功率放大器中的模式不稳定现象,结果表明,全光纤结构主振荡功率放大器中的模式不稳定现象会导致放大器斜率效率下降;理论计算表明,对于20/400阶跃折射率大模场双包层掺镱光纤,注入种子功率在百瓦左右时,模式不稳定发生的阈值功率在1kW左右:热效应是模式不稳定现象发生的根源。     

典型放电气体的击穿场强阈值研究

为了研究等离子体产生时的气体击穿特性,利用低气压条件下气体击穿场强阈值模型,分析了He、Ne、Ar、Kr、Xe和Hg蒸汽等6种典型放电气体的击穿阈值随入射波频率、电子温度、气体压强以及气体温度的变化规律。结果表明:气体击穿阈值随气体压强的增大而减小,随气体温度、电子温度和入射脉冲频率的增大而增大。气体压强和入射频率对击穿阈值的影响大于气体温度和电子温度,在所考虑的范围内,气体压强对击穿场强的影响约为100 V/m,入射脉冲频率对击穿场强的影响为50~300 V/m,气体温度和电子温度对击穿场强的影响为20~30 V/m。当考虑气体压强、气体温度以及电子温度等因素的影响时,各种气体的击穿场强阈值产生的变化规律相类似;但考虑入射频率的影响时,不同气体的击穿场强阈值差异很大。在所考虑的典型放电气体中,Xe具有最低的击穿场强阈值,He的击穿阈值最大。