What is the working principle of a CO2 laser cutting machine?

A CO2 laser is a gas laser that generates a cutting beam by electrically exciting a mixture of carbon dioxide, nitrogen (10-20%), helium, and trace amounts of hydrogen and xenon. The beam emits infrared light with a wavelength of 10.6 µm through a multi-mirror bellows delivery system and is focused onto the material surface through a nozzle.

Since the 1970s, CO2 laser technology has been the dominant technology in sheet metal cutting and remains the industry standard for processing non-metallic materials. The first CO2 laser prototypes date back to 1960, and industrial laser cutting machines began to be widely used in the 1980s. Although fiber lasers were developed in the late 1970s, they only became commercially competitive in metal cutting in the early 21st century.

The generation mechanism follows four steps:

Electric field excitation—Applying an electric field causes nitrogen molecules in the gas mixture to vibrate at high frequencies.

Resonant energy transfer—The vibrational energy of the nitrogen molecules is transferred to carbon dioxide molecules through molecular collisions.

Photon Emission—Carbon dioxide molecules collide with helium atoms, releasing photons as infrared light with a wavelength of 10.6 µm.

Beam Delivery—The beam passes through a multi-mirror bellows delivery system and is focused onto the material surface through a nozzle.

The output power of a carbon dioxide laser increases with the length of the gas tube, allowing the technology to be easily scaled linearly. Carbon dioxide systems can also have their pulse power increased through Q-factor tuning, exceeding continuous-wave output levels. Power ranges from tens of watts for engraving and marking applications to approximately 100 kilowatts for heavy industrial cutting—although high-power carbon dioxide devices produce lower-quality beams unless the gas tube is extremely long. These characteristics—simplicity, scalability, and a wide power range—explain why this technology has maintained its dominance in industry for over four decades.