Fiber optics for the delivery of 3 and 10.6 micron energy for laser surgery

Since the first infrared (IR) fibers were fabricated in 1976, there has been a strong desire to use these fibers for the delivery of laser power in less-invasive laser surgical procedures. This has been a difficult challenge and today no IR fiber has optical and mechanical properties even close to that of silica fiber. Nevertheless, the need for an IR fiber for medical CO₂ and Er:YAG lasers requires medical laser companies and clinicians to adopt often less than ideal IR fiber technologies. In this paper, the authors review the state-of-the-art in IR fibers for laser power delivery at 3 and 10.6 μm. The best power delivery fibers for the CO₂ laser are hollow waveguides. Hollow sapphire fibers are currently used in gynecological, orthopedic, and neurosurgical applications. The authors have used the hollow sapphire in their neurosurgical studies on brain tissue to deliver over 25 W of CO² laser power to tissue. There are several fibers of choice for the Er:YAG laser. One type is the heavy-metal fluoride glass fiber and the other is solid sapphire fiber. Sapphire fibers are fabricated using either a laser-heated-pedesta1 growth (LHPG) or edge-defined, film fed growth (EFG) technique. The former has produced the lowest loss fiber to date but the EFG process developed by Saphikon Inc. has promise of producing low-loss fiber in long lengths. The best LHPG sapphire fiber has a loss less than 1 dB/m and may be made in diameters from 100 to 400 μm. In power tests in their lab, the authors have delivered over 600 mJ of Er:YAG laser energy through a 50-cm long LHPG sapphire fiber. We have also used this fiber in some ophthalmic studies to study the ablation of tissue in eye-bank eyes. In general, we have found that the fiber functions well in a wet field and that we can ablate tissue using over 100 mJ without damage to the fiber end