Fabrication of PEEK Ag/AgI mid-infrared hollow fiber and transmission reliability study for CO₂ laser radiation

Hollow fiber is a crucial means for delivery of mid-infrared laser radiation and has a wide range of applications in laser surgery and other fields. At present, there is still a lack of low-cost, highly flexible plastic hollow fiber that can reliably transmit mid-infrared laser with low loss. In this study, flexible Poly ether ether ketone (PEEK) tubing material was selected as the structural tube for establishing a robust plastic Ag/AgI mid-infrared hollow fiber. Fiber samples with inner diameters of 1.0, 1.5 and 2.0 mm were prepared using plasma treatment and dynamic chemical liquid deposition processes. The transmission losses for CO₂ laser of the 1.0-, 1.5- and 2.0-mm-bore PEEK Ag/AgI hollow fibers increased from 0.40, 0.18 and 0.10 dB/m to 2.35, 1.60 and 1.05 dB/m, respectively, as they were bent at an angle from 0° to 180° with a radius of 15 cm. The hollow fibers could stably transmit CO₂ laser in high (120 °C) and low (-78.5 °C) temperature environments. After undergoing 100 h of accelerated humidity-heat aging (85 °C, 85 % RH) and 10 cycles of high-low (-40 ∼ 85 °C) temperature cycling treatment, the transmission loss remained almost unchanged. The PEEK Ag/AgI hollow fiber exhibited high energy damage threshold and it could stably deliver a 10 ∼ 20 W CO₂ laser beam for 20 min to 5 h when bent at a 25 cm radius and a 90° angle. The current research provides a possible approach for developing low-cost, highly flexible, low-loss and highly reliable mid-infrared hollow fibers. It is helpful to promote the applications of CO₂ laser in laser medicine, intelligent manufacturing and sensing.