For CO2 laser marking machines, the quality and performance of the laser tube directly impacts the machine's operating efficiency, the laser tube is also one of the most critical components. CO2 glass laser tubes are typically made of hard glass and adopt casing structure. The inner layer is the discharge tube, the second layer is the water-cooling jacket, and the outer layer is the gas storage tube. The discharge tube diameter of a CO2 laser is larger than that of a He-Ne laser tube. The thickness of the discharge tube generally has no effect on output power. The main consideration is the diffraction effect caused by the laser spot, and the tube length should be adjusted accordingly. Longer tubes should be thicker, while shorter tubes should be thinner. Discharge tube length is directly proportional to laser power output. Within a certain length range, the output power per meter of discharge tube increases with the total length. The purpose of adding a water-cooling jacket is to cool the working gas and stabilize the output power.
1. Hard Glass: This component is made of GG17 material, which is fired into a discharge tube, a water-cooling jacket, a gas storage jacket, and a gas return tube. Sealed CO2 glass laser tubes typically have a three-layer casing structure. The inner layer is the discharge tube, the middle layer is the water purification jacket, and the outer layer is the gas storage jacket. The gas return tube connects the discharge tube and the gas storage tube.
2. Resonant cavity: This component consists of a total reflector and an output reflector. The total reflector of the resonant cavity is generally based on optical glass with a gold film on the surface. The gold film reflector has a reflectivity of over 98% around 10.6µm laser beam. The output reflector of the resonant cavity is generally made of germanium (Ge), a material that transmits infrared radiation at 10.6µm, with a multilayer coating on the top.
3. Electrode: CO2 glass laser tubes generally use a cold cathode in a cylindrical shape. The choice of cathode material has a significant impact on the laser's lifespan. The basic requirements for the cathode material are low sputtering rate and low gas absorption rate.
The discharge tube is connected to a gas storage tube at both ends. A small hole at one end of the gas storage tube connects to the discharge tube, while the other end is connected to the discharge tube via a spiral gas return tube. This allows gas to circulate between the discharge tube and the gas storage tube, allowing for constant exchange of gas within the discharge tube. The glass laser tube is widely used for marking and engraving non-metallic materials such as acrylic and plastics, and has also been developed to be capable of marking electroplated mild steel. CO2 glass laser tubes are also used in automation systems to mark polyimide and polyester sheets used in flexible circuit boards and membranes for electronic instruments.