Importantly note that CO2 lasers use carbon dioxide as well as Helium & Nitrogen as its active medium. The TEA stands for Transverse Excitation at atmospheric pressure. Therefore the helium gas is used in CO2 lasers. The operating frequency for CO2 laser is about 10% normally but theoretically it could be much higher. Here Nitrogen gas acts as a buffer gas. . The pre-mixed gases are fed continuously into the tube forming the laser cavity. [CDATA[// >