Repetitive operation of a helium-free mini TEA CO2 laser

A helium-free mini TEA CO₂ laser has been operated at a repetition rate of 100 Hz wherein the gas re-circulatory loop consisting of heat exchanger and catalytic converter, mandatory for conventional repetitive operation of such lasers, have been totally dispensed with. The laser utilized inexpensive molecular gases alone that were simply flown out transversely through the inter-electrode region by an open gas flow system. The active medium was energized by making use of a spiker-sustainer excitation scheme. At this repetition rate, the laser produced an average power of 3.50 W.     

TEA CO2激光器非对称电极系统的电场分布

设计了一种非对称电极,这种非对称电极的阳极是Chang电极或Ernst电极,阴极是由直线和圆弧构成的简单电极。通过比较和分析非对称电极和对称电极的特点发现,非对称电极系统中简单电极的边缘电场起伏最大。采用有限元方法计算了非对称电极系统中的简单电极取不同的直线长度和弧线半径时,非对称电极系统的电场分布,给出了选择非对称电极系统中的简单电极参数的依据。结果表明：这种非对称电极系统结合了解析电极和简单电极的优点,通过选择非对称电极系统的简单电极参数,它可以在TEA CO2激光器中产生边缘电场起伏小于0.06,且满足电极表面均匀场面积宽度要求的电场。     

Towards a triggerable switchless TEA CO2 laser

The possibility of triggering a switch-less TE gas laser has been experimentally explored. To this end, the parallel spark preioniser array that functions as a switch of the switch-less laser has been optically triggered by transporting UV photons from the triggering discharge by means of an optical fiber. The maximum triggerable range was studied as a function of the number of spark channels in the triggering discharge and the gas composition in the triggered parallel spark preioniser.     

Mathematical modeling of CO2 TEA laser

Five and six-temperature models for the CO₂–N₂–He system are used to describe the process of the dynamic emission in the TEA CO₂ laser. All physical constants and relaxation rates related to these models are examined to estimate the output pulse parameters as a function of the input parameters. The two pumping processes implemented; empirical function and differential equation show a good agreement with the experimental data.     

管状预电离可调谐TEA CO2激光器

研制了一种新型的预电离结构——管状预电离器,并将其应用于可调谐TEA CO2激光器。利用光栅选线方案,采用光栅谐振腔,实现了激光的调谐输出。在输出耦合率为50%、气压为40 kPa的条件下,10P(20),10R(20),9P(20),9R(20)四条谱线获得的最高电光转换效率,分别为9.5%,9.7%,9.8%,9.8%。实现了激光器的高重复频率可调谐输出运转,测量了上述4条谱线激光输出的脉冲能量及平均功率,在输出耦合率为50%、气压为30 kPa的条件下,重复频率最高可达190 Hz, 此时的10P(20),10R(20),9P(20),9R(20)四线的平均功率分别为322,321,340,338 W。     

Synchronization of ultraviolet-preionization in a Marx-driven TEA CO2 laser

In a TEA CO₂ laser a two-stage spark gap was used to control the predischarge, which produced the ultraviolet-preionization, and to generate a trigger pulse for the Marx bank, which excited the main discharge. The time-sequence of the predischarge and the trigger pulse could be reversed so that the main discharge could commence before the preionization process. This set-up has enabled temporal synchronization on the laser performance, or basically the time delay between the pre- and the main discharges, to be investigated from about − 150 ns to 600 ns.     

An actively mode-locked TEA CO2 laser with multiline output

An actively mode-locked TEA CO₂ laser producing pulses consisting of more than 3 lines of the 10.4 μm band by inserting a KCl plate is described.     

Studies of a TEA CO2 laser with a cylindrical mirror unstable resonator

We describe the results of a study of a TEA CO₂ laser using a strip cylindrical unstable resonator which produces an output beam with suitable characteristics for producing a high quality line focus. Using this technique an irradiance of ?10⁹W cm^-2 over a 5 cm long line focus has been achieved.     

Various techniques for multiline operation of TEA CO2 lasers

The various techniques used for multiline operation of TEA CO₂ lasers are reviewed with particular reference to the multiline laser parameters of interest in laser applications.     

High power TEA CO2 laser tuned by a holographic grating

Wavelength tuning of a TEA CO₂ laser by means of a holographic grating with sinusoidal profile is reported for the first time. The grating with 136 lines/mm had an optimized efficiency according to the gain of the laser. The laser beam was coupled out through the zeroth grating order.     

Construction and performance characteristics of a rapid discharge TEA CO2 laser

Experimental determination of the non-linear susceptibility coefficients χ^NL_ij responsible for second harmonic generation in some layered compounds excited at 0.6943 μm and at 1.06 μm is reported. A strong dependence of the magnitudes of χ^NL_ij upon the material energy gap is observed. This agrees with the predictions of quantum-mechanical analysis.     

Configuration analysis of the resonator in a double-pulse TEA CO2 laser

This paper describes the resonator configuration of a double-pulse TEA CO₂ laser, and discusses how to obtain single-mode operation in that configuration.     

Single mode oscillation of TEA CO2 laser with an interference resonator

An effective single-longitudinal mode (SLM) pulse TEA CO₂ laser operation was demonstrated using a Michelson’s type resonator with a tilting Fabry-Perot etalon. A modified numerical model of the interference resonator was investigated for designing the laser. The experimentally measured values were found to have good agreement with the numerical model. A pulse width of about 90 ns and the maximum pulse energy of about 300 mJ were achieved at 10.59 μm in SLM and TEM₀₀ mode. The reliability of producing SLM pulses was 100% and there was no damage on the etalon. By turning the interference resonator, the SLM output was tuned 44 lines of the CO₂ spectrum.     

高功率TEA CO2激光器两波长激光切换输出技术

以TEA CO2激光器通常采用的平-凹光学稳定腔为基础,提出了一种新的波长选支方法——输出窗口镀膜选支方法。利用一台高平均功率TEA CO2激光器进行了选支实验研究,结合现有光学镀膜技术,得到了中心波长为9.3 μm的激光单谱线输出,其单脉冲能量及平均功率与激光器原中心波长10.6 μm单谱线输出的相应参数基本相当。研究发现,以相同单脉冲能量激光照射热敏纸时,中心波长9.3 μm激光光斑与中心波长10.6 μm的明显不同。同时,还设计出两波长窗口密闭免调切换装置,在一台激光器上实现了10.6,9.3 μm两个中心波长激光同等功率水平的免调切换输出,切换位置误差小于5″,密封性能满足使用要求。     

A sensitive arc detection technique for reliable operation of high repetition rate TEA CO2 laser

A simple and sensitive technique, which utilizes the sensing of both the discharge current and the visible light emission from the discharge, has been developed to detect the arc formation during the operation of a high repetition rate TEA CO₂ laser. It is shown that the optical detection in the visible spectral region is more sensitive than that it is in the UV region and hence can be used more effectively to monitor the onset of arc formation, while the current signal is useful in the strong arc formation regime. We demonstrate that the trigger signals generated by both the methods can be employed for reliable protection of the laser system from catastrophic damage due to deleterious arc formation.     

TEA CO2激光器预电离结构电极系统的电场研究

高功率气体激光器的非对称复杂电极系统中,电极参数的变化以及预电离结构的引入将会使所设计的均匀电场发生具体的改变。采用高精度有限元方法,对这类复杂电极系统进行建模并且计算其电场分布,根据分析结果更合理地指导激光器设计。对一种典型的非对称复杂电极系统TEA CO2激光器,应用该方法并结合了预电离过程,研究了引入预电离器导体和变化电极形状对电极表面的电场强度起伏和放电空间的均匀电场面积产生的影响。结果表明:通过这种预先模拟,合理选择电极构型参数和预电离结构安装位置,可以产生性质较好的均匀电场以及效率较高的激光输出。     

A 10 cm aperture,high quality TEA CO2 laser

Experiments have been performed on a corona preionization type 10 cm aperture TEA CO₂ laser. For a CO₂:N₂:He=1: 1: 7: mixture an output energy of 34 joule per liter and for a 1 : 1 : 10 mixture 40 joule per liter could be obtained. The overall efficiency is about 18%. The time behaviour of the current and voltage of the system shows a delay of several hundreds of nanoseconds after the preionization peak, which indicates a relatively low initial electron-density level. Neverthe less, it proved to be high enough to obtain a very homogeneous discharge and reproducible output energy.     

A compact,sealed, single mode TEA CO2 laser

A compact, sealed, TEA-CO₂ laser utilizing a double-discharge technique has been constructed and operated under single-mode conditions. Sealed operational lifetimes exceeding 10⁶ pulses have been obtained by the addition of small quantities of hydrogen and CO to the initial gas mixtures. It has also been found that operation without helium is possible giving single-mode output energies of about 20 mJ/pulse at peak powers of about 150 kW. The pulse repetition frequency was 0.5 s^-1. The use of an 18 cm long laser cavity allowed the oscillation of only one longitudinal mode when the frequency of the cavity was tuned closely to the CO₂ line centre frequency. An iris was used to restrict transverse modes to the TEM₀₀. Beat frequency measurements using a stable, CW CO₂ laser indicate a “chirp” of about 5–6 MHz/μs in the tail of the pulse.     

Performance of a self-switched TEA CO2 laser with multi/two/single spark channel preioniser

Satisfactory performance of a TEA CO₂ laser of active length 30 cm is reported when self-switched by its own preioniser comprising two mutually coupled parallel spark channels or even one spark channel. A comparison of the performance of the laser with respect to the maximum extractable energy and electro-optic efficiency as a function of number of preionising spark channels is presented. With reduced number of mutually coupled parallel spark channels, the operation approaches the near ballast-free regime, resulting thereby, in an improved performance of the laser.