The output from RF supply is coupled to a number of electrodes that are space around the laser tube. The figure shows that pumping power is provided an RF power supply. Therefore CO2 gas laser is considered the type of molecular gas laser. At each end of the discharge tube is an adjustable mirror attached through a flexible bellow to the tube. This can be done by cooling the gas. In this mixture the helium and nitrogen work in concert with the CO2 to produce the desired lasing effect. It is a four level laser and it operates at 10.6 μm in the far IR region. The TEA stands for Transverse Excitation at atmospheric pressure. The process of laser emission by the fall of CO2 and N2 through different energy levels is shown in Fig. The CO2 laser can be operated in either CW or Pulse mode commonly. Penetration in pulse beam welding is also governed by material proper­ties. By diagram sealed tube design can be shown as: If DC excitation is used with the sealed tube CO2 laser then it is much like constructed as He-Ne gas laser, however it is necessary to have an elaborate cooling system with the laser. Here Nitrogen gas acts as a buffer gas. 14.25. The direct vibrational excitation of CO2 by an electric discharge is inefficient. Its application is as follows. Heavier sections may be welded in two passes, one from each side. Copyright 10. Now when this CO2 molecule drops from an excited level to another level then lasing occurs. Cooling system requirement in some configurations also a disadvantage. In this way buffer gas is needed in CO2 gas lasers. To minimise the operat­ing costs a gas-to-liquid heat exchanger is used and the laser gases are re­-circulated in the system as shown for an axial flow CO2 laser in Fig. [CDATA[> It was the first molecular gas laser developed by Indian born American scientist Prof.C.K.N.Pillai. Content Guidelines 2. Plagiarism Prevention 4. Only a small quantity of gas is consumed due to the need for continual re­moval and replenishment of a small amount of the laser gas mixture to prevent build-up of contaminants generated by the dissociation of CO2 and N2 in the electric discharges. Current flow through the tube is perpendicular to the movement of the gas. CO2 lasers can operate both in the pulsed wave (PW) and the continu­ous wave (CW) modes. This energy is then removed as waste heat. They are also quite efficient: the ratio of output power to pump power can be as large as 20%. Transitions can occur between vibrational energy levels with different rotational levels, so there are many lasing lines around the main vibrational transitions.