Studies On Mechanisms Of Power Decreased In A High Power Transverse-Flow CO₂ Laser

High power transverse-flow CO₂ lasers are playing more and moreimportant roles in medicine, military affairs and industry processes, such aslaser cutting, welding and heat treatment. This paper focuses on themechanism studies of the transverse-flow CO₂ laser power degraded afterworking period of time. Followed reviewing developments of the highpower CO₂ lasers on the designs and fabrications in our country, some keytechnologies and improvements on the pumping sources, discharge modes,high gas pressures and gaseous flow directions of the CO₂ lasers in theworld are also described in the first chapter. Then, the configuration of atransverse-flow CW CO₂ laser (GFT-ⅣB, 7kw), made by ShangHai LeoLaser Equipment Co.Ltd, is shown in details in chapter 2. Thetransverse-flow CW CO₂ laser is equipped in the Center for LasingProcessing in the College of Mechanical Engineering, Zhejiang Universityof Technology. A method to determine the gas compositions and their ratiosin the laser resonator after long-term discharge is presented in the chapter 3.The variations of the concentration of gaseous mixtures (CO₂, CO and O₂) in the laser resonator with the operating lapsed time are determined byexperiments. Chapter 3 discusses the mechanisms of the laser powerdegraded after long-term discharge based on the laser kinetics theory, andsome measurements defending the laser power decreased are also presentedin this chapter. In addition, the mechanisms of the high powertransverse-flow CO₂ laser kinetics are discussed in chapter 4. The rateequations for the laser plasma parameters, such as the laser-levelpopulation, the electron temperature and the electron density in the highpower transverse-flow CW CO₂ lasers, are established and solved by usinga numerical method in chapter 4. Therefore, the laser small-signal gain, thesaturation intensity and the laser output power are also obtained,accordingly, where a MATLAB computer program is developed, asenclosed in Appendix 1.