Frequency chirp in a 10 ATM RF-excited CO2 waveguidelaser

Various mechanisms causing frequency chirping in multiatmospheric-pressure CO₂ lasers are discussed. The frequency chirp has been measured in a pulsed 10 atm CO₂ waveguide laser. It has been found that the dominating cause of the frequency chirp in this laser is heating of the gas by the RF discharge. The chirp increases with increasing RF input power. The chirp levels off at about 100-150 MHz/μs for 25 kW of input power. This leveling off the chirp is believed to be due to the negative lensing effect of the gas density perturbation. The effect of the anomalous dispersion on the chirp is observed when the laser is operated at the flanks of the CO₂ gain branches     

同轴射频激励CO2激光器的热效应研究

通过求解放电等离子体中的带电粒子密度和能量的平衡方程、电流连续性方程以及热传导方程,研究了同轴射频(RF)激励CO2激光器中放电混合气体的温度效应,分析了有关放电参数对温度分布的影响。     

高气压连续CO2激光器的输出功率

<正>随气体压力增加,单位时间流过激光器的激活介质增加,可望获得较大的输出功率,并能改善器件的封闭寿命和输出稳定性.待研究的装置见图1.在些装置中,以金属板ABCD为阳极,EFGK为阴极(可以是管、板或针状),极问距离AE=H.假定电子密度n在正柱区     

Continuously tunable high-pressure RF-excited CO2waveguide laser

The design and frequency tuning characteristics of a pulsed RF-excited CO2waveguide laser operating at 10 atm are reported. Continuous tunability has been obtained over a 300 GHz wide spectral range from theR(12)to theR(26)line in the 10.4 μm band. The laser output has good temporal and spectral characteristics.     

A CW CO2 laser with DC-discharge preionization

The application of the plasma-injection technique (involving DC-discharge preionization) to a CW CO₂ laser operating with recirculated gas is described. Measured characteristics of the discharges, the gain, and the output power are presented. An output of 110 W was obtained with a specific efficiency of 1.0 J/l^-1 of flowed gas at a pressure of 10 kPa. A simplified model to calculate a characteristic length of the main discharge, which is useful for design purposes, is developed. This type of laser may be scaled simply to higher output powers, requires a gas mixture with only 20% He, is compact and robust, and yet is simple in its electrical and mechanical requirements     

无He横流连续CO2激光器的新进展

在横流CO2激光器中,我们以Ar(CO2-N2-Ar)代He(CO2-N2-He)实现了1kW连续激光输出,并获得以CO2-N2实现了1.2kW连续激光输出的稳定运行。     

硅中注砷的连续CO_2激光退火的研究

利用高功率连续CO_2激光定点辐照,对砷离子注入的硅片进行退火。实验结果表明晶格损伤得到了完全恢复,注入砷原子的替位率与电激活率高,还克服了激光聚焦扫描退火时引起硅片表面变形的问题。     

TEACO_2激光器主动锁模的实验研究

利用一米长光预电离 TEA CO_2激光器,腔内置一布氏角声光调制器做损耗元件,进行锁模实验研究。叙述了设计考虑、实验装置及测试结果。     

CW 20-kW SAGE CO2 laser for industrial use

A CW CO₂ laser with power output of more than 20 kW is described. The laser consists of a discharge excitation system named SAGE (Silent-discharge Assisted Glow discharge Excitation) and a ZnSe or KCl transmissive window for extracting high-quality beams with axisymmetric intensity profile from a confocal positive-branch unstable resonator. SAGE is effective in forming a uniformly distributed and stable discharge in a large-volume, high-pressure gas excitation medium. Together with appropriate high-pressure gas conditions and a properly selected zeolite to adsorb water vapor in the laser chamber, the transmissive windows enable gas-sealed operations. The structure of the 20-kW SAGE laser and its performance characteristics are described. The maximum CW power of 26.5 kW with an efficiency of 16.5% is attained with the ZnSe window, and a 20.3-kW power output is extracted through the KCl window. Long-term gas-sealed operation at a CW power level of 20 kW has been demonstrated for a period of 65 h     

高效率横向电激励连续CO_2激光器的研究

报道一种工业用高气压封闭形横向电激励二千瓦级连续CO_2激光器。连续运行13小时,输出功率高于2.3kW,能量转换效率大于17％。研究了放电特性、输出特性;测量了在不同放电条件下的电子温度和电子浓度。     

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     

二千瓦级横向电激励CO_2连续激光器

我们研制的HGL-81型CO_2激光器输出功率达2千瓦以上,连续工作时间2小时以上,输出功率稳定度小于±5％,电光转换效率大于11％。 HGL-81型CO_2激光器采用的总体技术方案是工作气体快速流动,横向电激励、高气压、多针-板自持放电。工作气压范围为50～300托。提高工作气压的好处是:激光输出功率随气压增加而增加,有利于长时间、全封闭稳定工作,工作过程中不需要补充新鲜气体,纵模稳定;气体质量流量大,气体温度低等。提高工作气压带来的主要问题是辉光放电的不稳定性。我们采用多针-板放电结构较好地解决了这个问题。     

High-Quality Flat-Top Micromachining of Silica by a CW CO2 Laser

This letter demonstrates a simple and fast technique that dramatically improves the micromachined surface quality of silica substrates processed by a continuous-wave CO₂ laser. When sufficient laser power is directed at the surface of a sample, its temperature increases beyond the boiling point. Melted material is ejected and a groove is created. Some of the ablated material redeposits on each side of the groove, altering the surface quality of the substrate. To circumvent this problem, we deposit a polymer overlay as a sacrificial film which protects the surface during the ablation process, resulting in a flat surface on either side of the groove at very high writing speeds. The grooves can be used as an aid to passive alignment for an optical fiber, as diffractive optical elements or to create high-quality microfluidic chips     

Preionizer-induced pulsed-mode operation of a transverse-flowtransversely excited CW CO2 laser

A pulse-preionized, dc-excited, transverse-flow, CW CO₂ laser has been operated in pulsed mode without using a discharge power-switching scheme. The pulsation in laser power is produced by a pulsed current that flows from the dc power supply due to the collapse in the discharge impedance whenever a preionizer pulse appears. By properly choosing the preionizer-pulse repetition frequency, dc power-supply filter-capacitor value, and gas composition, the laser pulsation has been enhanced. This laser has been operated at 1-kW average laser power level in pulsed mode at 1.3-kHz pulse repetition frequency with a peak-to-average power ratio of 3.35 and laser-power modulation depth of almost 100%     

1kW无氦横流连续CO_2激光器的研究

本文报道我们研制的 Ikw无 He横流连续CO_2激光器的实验结果。激光器总体结构如图1所示。其放电装置采用针板放电结构，阴极由152根直径为      

Single-mode pulses from a high-pressure CO2 laseroperated below emission threshold

The authors describe a simple modification to the injection seeding method which has proved experimentally to yield reliable, single-mode emission from a 10-atm CO₂ laser without the need for cavity length tuning. The technique consists of choosing the laser parameters such that the power oscillator is operated slightly below emission threshold, even though the gain can be above threshold for a short time following excitation. Under such circumstances, the initial laser power due to spontaneous emission is too weak to be amplified to a significant level during the period where the gain exceeds the losses. If a more intense external signal is injected into the laser, it can be regeneratively amplified to much higher powers, eventually extracting a substantial fraction of the available laser energy     

黑体泵浦CO_2-CO,N_2O-CO,CO_2-H_2O和N_2O-H_2O激光的研究

本文对黑体辐射泵浦CO_2激光和N_2O激光由于CO和H_2O的加入所引起的激光功率变化进行了理论和实验研究.CO的加入可使的N_2O激光功率增加28%.     

Continuously tunable high-pressure CO2 laser forspectroscopic studies on trace gases

A high-pressure CO₂ laser with unique characteristics in terms of continuous tunability and emission bandwidth is presented. It is operated at a pressure of 11.5 bar and transversely excited by short, high-voltage pulses generated by a double LC inversion circuit. Auxiliary discharges parallel to the electrodes provide a sufficient free-electron density through UV ionization of the laser gas mixture. The laser resonator consists of a near-grazing-incidence grating setup in which the grating is positioned at a large incidence angle of 77°. A theoretical model for the calculation of the emission bandwidth is presented and its predictions are compared to direct measurements and show excellent agreement. The achieved very narrow bandwidth of 0.018 cm^-1 constitutes the ultimate wavelength resolution of any detection system using this laser as radiation source. It allows the resolution of any fine structure in the spectra of absorbing gases at atmospheric pressure. Continuous tunability has been achieved over 76 cm^-1 between 932 cm^-1 and 1088 cm ^-1 with minimum pulse energies in excess of 10 mJ. The narrow bandwidth precludes the occurrence of mode-pulling effects so that the laser exhibits a linear wavelength tuning behavior throughout the entire emission range. The calibration of the laser wavelength is performed by photoacoustic measurements on low pressure CO₂ gas. An absolute accuracy of ±10^-2 cm^-1 is achieved. A great potential improvement in detection selectivity can thus be expected from a scheme with the high-pressure CO₂ laser as radiation source     

横流CO_2激光器的二维增益分布

用一维气流、准二维放电模型算出垂直于电极平面的等增益线二维分布。研究了放电区气体流速、放电参数以及气体成分等对小信号增益沿流动方向变化规律的影响。对于每一气体压力,有与最佳增益曲线对应的流速范围。将计算结果与实验结果进行了比较。     

大孔径稳腔连续注入式TEACO_2激光器

本文描述了一台谱线可调大孔径稳腔连续注入TEACO_2激光器,对激光器的运转特性进行了实验研究和理论分析,并定性分析了实现单频输出的可行性.