In any CO2 laser system, mirrors are among the most critical components. The design and manufacturing quality of the laser’s mirrors are crucial to generation, maintaining and delivering a high-quality laser beam. There are two main categories of laser mirrors: internal and external.
Internal mirrors are used to generate, maintain and amplify the laser beam by forming a reflective “resonator” around the excited CO2 gas mixture. Internal mirrors are sometimes called resonator or cavity mirrors.
External mirrors are used to deliver, manipulate and focus the laser beam. Most mirrors have flat reflective surfaces, but some have curved surfaces designed to reduce beam divergence. The design of the substrate material and coating of a CO2 laser mirror is primarily determined by its intended function.
For CO2 lasers, several substrate materials are available. Silicon is used on low to medium power systems when cost is a big consideration. Copper, with its superior thermal conductivity is used for high-power systems. Molybdenum is used in dirty environments where durability and repeated cleanings are required.