Polymer / glass hollow-core photonic band gap fibers for infrared laser beam delivery

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Bilkent University
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Photonic band gap fibers are proposed for the medical applications of laser light transmission into body. Conventional optical fibers guide light via total internal reflection. Due to light guiding mechanisms and materials they have limited frequency range, fiber flexibility and laser power. On the other hand, it is possible to scale operating wavelengths of PBG fibers just by changing a few parameters during fabrication process. Besides, hollow core of PBG fibers eliminates material absorptions and non-linearities during light guiding. PBG fiber production starts from material characterization; and selection; and continues with fiber design, thin film coating, preform preparation and fiber drawing. Studies on theoretical calculations and material properties have shown that best candidate materials for CO2 laser delivery are As2Se3 and poly-ethersulfone (PES). For this purpose, As2Se3 coated PES films are rolled to form a preform and consolidated before thermal drawing. Characterization of drawn fibers indicated that CO2 laser can be transmitted with loss levels of > 1 dB/m and 32 W output power is observed from a 1.2 m long fiber. After fabrication and characterization of PBG fibers, a prototype infrared laser system is built and tested on various applications. In our group laser tissue interactions are examined to see effectiveness of CO2 laser on tumor tissue. Experiments showed that tumor tissue is affected in a very distinctive way compared to healthy tissue. Absorption of cancerous lung tissue at CO2 laser wavelength (10.6 µm) is higher than absorption of healthy tissue at the same wavelength. This study proposes a wide use of PBG fiber for not just CO2 lasers, but also other laser systems used in different medical operations, such as Ho:YAG lasers. PBG fibers for high power laser delivery are novel structures for fast, painless and bloodless surgeries.

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Photonic Band Gap Fiber, Hollow-core Waveguide, Chalcogenide Glasses, Medical Lasers, High-Power Laser Beam Delivery
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