A magnetically stabilized coaxial laser discharge

A new magnetic discharge stabilization technique for coaxial laser systems is described. The approach utilizes crosses electric and magnetic fields to create and maintain a large and rapidly rotating plasma volume which does not experience glow-to-arc transitions. Very high cw specific discharge power loadings have been achieved even without the benefit of external gas cooling or circulation.Performance is insensitive to gas composition and pressure such that high power coaxial discharges have been run in CO₂ laser gas mixtures up to several hundred torr. Stable cw discharges have also been obtained in mixtures containing several torr of SF₆.The technique appears to be readily scalable to give very large excited volumes in systems with comparatively small overall physical dimensions.     

Multipass coaxial radiofrequency discharge CO2 laser

We report the design and performance characteristics of a carbon dioxide laser excited by a radial radiofrequency static gas discharge. Power extraction of 20 W is obtained using a multipass optical system, matched to a 13 cm long annular discharge gain region, within a linear stable resonator.     

脉冲放电激励的钡蒸气激光的研究

设计和制作了新型结构的金属蒸气激光放电管.用钡为激光介质,通过纵向高频快脉冲放电激励,在国内首次实现波长为113μm和150μm的红外钡蒸气激光振荡,激光成分主要集中在150μm这条谱线上,激光输出功率和功率密度分别达12W和333mWcm3.测量并讨论了各工作参量和激光输出特性之间的关系     

全气相化学激光体系的直流放电研究

 为了提高化学激光体系(AGIL)中F原子的产率，采用直流放电引发方式，对棒式电极的放电特性进行了研究。在对NF3/He混合气体进行解离时，通过选择不同平衡电阻，得到了3 kW左右的放电注入功率。用光谱分析仪对F原子产率进行了测量。通过拟合计算可得：一个NF3分子能够解离出1.3～1.5个F原子。     

A copper iodide laser excited by transverse discharge

Operation of a copper iodide laser in a transverse-discharge configuration is reported. Oscillation occurs on both the 5106 and 5782 Å transitions of neutral copper over a wide range of discharge parameters, including buffer gas pressures up to one full atmosphere. Laser pulse energies of 5 μJ per cm³ of active volume (total active volume ≈ 100 cm³) have been obtained and preliminary investigations suggest that this type of device can be scaled to larger active volumes and greater output energies.     

全气相化学激光体系的直流放电研究

为了提高化学激光体系(AGIL)中F原子的产率,采用直流放电引发方式,对棒式电极的放电特性进行了研究。在对NF3/He混合气体进行解离时,通过选择不同平衡电阻,得到了3 kW左右的放电注入功率。用光谱分析仪对F原子产率进行了测量。通过拟合计算可得：一个NF3分子能够解离出1.3～1.5个F原子。     

脉冲放电激励的钡蒸气激光的研究

设计和制作了新型结构的金属蒸气激光放电管.用钡为激光介质,通过纵向高频快脉冲放电激励,在国内首次实现波长为1.13μm和1.50μm的红外钡蒸气激光振荡,激光成分主要集中在1.50μm这条谱线上,激光输出功率和功率密度分别达1.2W和33.3mW/cm3.测量并讨论了各工作参量和激光输出特性之间的关系.     

Flash-lamp pumped dye laser excited by a transverse discharge

A flash-lamp pumped dye laser has been described in which the discharge responsible for the working medium excitation was transverse to the capillary filled with the dye. It was shown that such arrangement allows for the lamp operation at the atmospheric pressure and makes possible generation of short pulses of light.     

Effective nonchain HF laser excited by a self-sustained discharge

Lasing and discharge in mixtures of SF₆ with hydrogen and hydrocarbons are investigated. If the chemical reaction is initiated by a self-sustained discharge (a generator with both an inductive and capacitive energy storage can be used), the maximum lasing efficiency is attained at high values of the ratio E/p (where E is the electric field intensity and p is the pressure in the mixture) if shaped electrodes and preionization of the discharge gap are employed. For the first time, the lasing efficiency obtained in a nonchain HF laser is as high as 10% of the energy deposit and 4.5% of the stored energy for a specific radiation energy of ≈140 J/(l atm). At high efficiencies, the emission spectrum of the nonchain HF laser significantly broadens and cascade lasing at P(3-2) → P(2-1) → P(1-0) vibrational transitions for several rotational lines is realized.     

放电泵浦ArF准分子激光动力学模拟与参数分析

利用一维流体模型研究了放电泵浦ArF准分子激光动力学过程,得到气体放电过程中放电电路的电流电压波形,得到了电子密度、光子密度、电场的时空分布特性,分析了放电参数对激光输出的影响。结果表明,电路参数、工作气压、氟气比例均对激光输出有显著影响,放电电路中的电感值对输出影响较小,参数范围较广,而电路中较小的峰化电容值有利于获得长脉冲输出,气压太大或太小都会使输出能量降低,同样,氟气比例太大或太小也会使输出能量降低。     

Self-reproducing ray-cluster and misalignment of gas laser resonator having a coaxial discharge chamber

A laser resonator with two annular spherical mirrors is studied. The self-reproducing mode of this resonator is established by means of a self-reproducing ray-cluster. Its existence condition and area are analyzed and provided for the first time. The resonator's adjusting accuracy is analyzed in detail and the relevant calculation for typical cases is illuminated. The tolerance of mirror center displacement from the axis of the coaxial discharge chamber is proved to be about 0-0.15 mm, and the tilt tolerance 0-6″, when resonator length L≈1 m, the radius of curvature of the two mirrors ρ≈5-10 L, and the loss of applicable radial width of the coaxial discharge chamber for light propagation is smaller than 1 mm. The object-image relation of the resonator and its application in adjustment of the resonator are also discussed.     

Numerical simulation of gas flow in a magnetically stabilized coaxial laser discharge

The neutral gas flow profile within a magnetically stabilized coaxial laser gas discharge is analyzed by using a single fluid magnetogasdynamic model. Equations describing the rotational, radial and axial gas transport are solved by using an iterative alternating direction implicit method. Steady state rotational velocities of the order of 20 m/s are found.     

Ionizations and fragmentations of benzene,methylbenzene, and chlorobenzene in strong IR and UV laser fields

Ionizations and fragmentations of benzene, methylbenzene, and chlorobenzene are studied in linearly polarized 50-fs,800-nm and 400-nm strong laser fields using a time-of-flight mass spectrometer. It is shown that at low laser intensity, the parent ions are dominant for any one of the molecules in an 800-nm strong laser field, while extensive fragmentation is observed in a 400-nm laser field, which can be understood by the resonant photon absorption of molecular cations. The ratio of the yield of the parent ion to the yield of the total ion for each molecule is measured as a function of laser intensity in a range from 1.0 × 1013W/cm2 to 4.0 × 1014W/cm2, in either the 800-nm or 400-nm laser field. The results show that the fragmentation of the aromatic molecules increases significantly as the laser intensity is increased. Possible mechanisms for fragmentation in strong laser fields are discussed. Finally, the saturation intensity of ionization of the titled molecules is also determined.     

Visible nonlinear band-edge luminescence in ZnSe and CdS excited by a mid-infrared free-electron laser

Visible nonlinear band-edge luminescence in ZnSe and CdS bulk crystals was observed upon excitation by a mid-infrared free-electron laser (mid-IR FEL) at approximately 9 mm. The emission intensity is proportional to the 74th and 45th powers of the excitation intensity for ZnSe and CdS, respectively. For ZnSe, the temporal profile of the emission intensity does not follow the profile of the excitation macropulse of the FEL, but sharply rises and decays only at the maximum of the macropulse profile. These features are in marked contrast to those of a previous report, where the emission profile follows that of the macropulse, and the emission intensity scales with the 4th power of the excitation intensity. The experimental observations were reproduced by a numerical simulation based on impact ionization and avalanche ionization by electrons accelerated by the optical electric field of the FEL. The large nonlinearity in the bandedge emission comes from the macropulse temporal structure, which consists of micropulses densely spaced to allow excited carriers to survive when the next micropulse arrives. They work as seed carriers in the next carrier multiplication step.     

Numerical modeling of a XeCl laser excited by microwave discharge

12 , 169 (1987). Reasonably good agreements in the peak output power and laser efficiency have been achieved. Model calculations also predict that an efficiency as high as 2.7% can be obtained once the conditions of the above-mentioned experiments have been optimized. From the consideration that the skin depth effectively limits the absorption length of the microwave pumping and hence the excitable volume, it is concluded that high input power densities (>2 MW/cm³) and higher gas pressures (between 3 and 10 atm) are the preferable conditions to achieve higher efficiency. Preliminary calculations on CCl₄ containing XeCl gas mixtures show that improvement in laser efficiency by several folds may be achieved as a result of the higher intrinsic efficiency of excimer formation. Received: 23 September 1996 / Revised version: 25 March 1997     

Supersonic CO2 laser excited by RF discharge in closed cycle

A supersonic gas flow having a Mach number of 2 has been realized in a closed-cycle radio-frequency (RF)-discharge-excited supersonic CO₂ laser system. Stable RF discharge at a high CO₂ gas concentration has become possible using supersonic gas flow and RF discharge generated between dielectric electrodes. As a result, high RF input power density has been obtained. In addition, a high small-signal gain has been obtained in the supersonic section through decreases in gas pressure and gas temperature due to supersonic gas flow.This revised version was published online in August 2005 with a corrected cover date.     

Emission characteristics of a high-power glow discharge plasma in a mixture of inert gases with bromine and iodine vapor

The results of an investigation of the UV radiation from the plasma of a dc glow discharge in mixtures of inert gases with bromine and iodine molecules are presented. The current-voltage and spectral characteristics of a longitudinal glow discharge with a power of 10–250 W are studied. The power and the efficiency of the total UV radiation of the plasma, as well as the power of radiation at the spectral line of the iodine atom at 206.2 nm, are optimized as functions of the power deposited into the plasma and the composition of the gas mixture. In active media based on Kr-Br₂ mixtures, the molecular emission of the plasma was represented by bands at 207 (KrBr(B-X)) and 289 nm (Br ₂ ^* ), while, in He-Xe-I₂ mixtures, it was represented by bands at 253 (XeI(B-X)) and 342 nm (I₂).     

Radiation trapping in an alkali-vapor-noble-gas mixture excited by a strong laser pulse

We analyze the nonlinear, non-stationary radiation trapping process in a cell filled with a noble gas and an alkali vapor excited by a short intense laser pulse. We derive analytical approximations for the total density of the excited atoms, and for the radiation emerging from the cell. The considered lineshapes are pure Doppler, Voigt, and pure Lorentzian profiles. We confirm that the emergent radiation can decay faster than with the natural lifetime of the atomic transition. We also show that as we increase the noble gas pressure, the decay of the emergent radiation becomes slower at early times and faster at late times.     

703-to 731-nm FI laser excited by a transverse inductive discharge

It is proposed to use a pulsed transverse inductive discharge for exciting gas lasers operating on electron transitions in atoms and molecules. An electron transition laser on fluorine (FI) atoms pumped by a transverse inductive discharge is developed. Lasing at three wavelengths (703.75, 712.79, and 731.1 nm) is obtained by exciting He-F₂ (NF₃) gas mixtures in a pressure range from 20 to 350 Torr. The results of experimental investigation of the spectral, temporal, and energy characteristics of the inductive FI laser are presented.