Gas lasers

Gas lasers were discovered almost simultaneously with solid-state lasers: in the infrared, the CO ₂ laser was discovered by Patel. In the visible, the helium-neon (He-Ne) laser immediately enjoyed great development. These lasers require relatively simple technical equipment: excitation is obtained by a high-voltage electrical discharge in a low-pressure gas (generally a sealed tube in the case of the He-Ne laser). Laser radiation is generally continuous, which was initially the unique feature of gas lasers.