Hollow fibers with interior coatings of metals and dielectrics are commonly used for laser power delivery. While inorganic coating materials typically have higher-temperature capability in the infrared (IR) region, organic coatings can perform in the visible and near-infrared regions. Unfortunately, the high refractive index of many organic coatings (2.1 up to 4.3) limits this wavelength performance; in addition, application of these coating materials often requires high-temperature processing steps that reduce fiber flexibility and durability. To combat these issues, researchers at Fudan University (Shanghai, China), Sendai National College of Technology, and Tohoku University (both in Sendai, Japan), have applied a low-index (1.41), room-temperature-processable dielectric material that enables broad-IR-range power-delivery hollow fibers with improved environmental stability.
The researchers selected OC300-a commercially available organic polymer from Omura Paint & Fine Chemicals (Japan)-for its wide-range thermal stability, water repellance, and physiological inertness. Using a room-temperature liquid-phase coating method for the two-part silicone polymer (polymer and hardener), the resultant hollow OC300 interior-coated fiber outperformed a 1.53 refractive index, high-temperature-processed cyclic olefin polymer organic coating. The OC300 fiber had lower loss and improved durability over the 0.5 to 10 µm wavelength range tested. Contact Yi-Wei Shi at [email protected].