A Focus Control System Based on Varifocal Mirror for CO2 Fiber-Coupled Laser Surgery

Fiber-coupled laser tools combine the precision of lasers with the flexibility of optical fibers. They have been used in surgical procedures, such as transoral microsurgery, to perform precise incisions in delicate structures that are often difficult to reach with other tools. Unfortunately, the performance of fiber tools is not akin to that of traditional laser systems. Prioritizing miniaturization, these tools typically use no optics and ablate tissue in near-contact mode, which induces significant level of tissue carbonization. To avoid this problem, we have developed a focus control system designed for fiber-coupled laser tools based on a microfabricated varifocal mirror. We have demonstrated the efficiency of the system by adjusting the focusing of a CO
₂
laser beam when ablating plaster block targets while varying the distance to the target within the range of 10mm to 25mm. The proposed system was able to ablate uniform lines, with an average width of 420
$\mu \text{m}$
and showed higher precision than fixed focus and bare fiber systems.