Ishii Yuya, Omori Keisho, Sakai Heisuke, Arakawa Yuki, Fukuda Mitsuo
Faculty of Fiber Science and Engineering, Kyoto Institute of Technology, Kyoto, Kyoto 606-8585, Japan.
Department of Electrical and Electronic Information Engineering and Department of Environmental and Life Sciences, Toyohashi University of Technology, Toyohashi, Aichi 441-8580, Japan.
ACS Omega. 2018 Jun 22;3(6):6787-6793. doi: 10.1021/acsomega.8b00835. eCollection 2018 Jun 30.
Wet-electrospun (WES) polymer micron and submicron fibers are promising building blocks for small, flexible optical fiber devices, such as waveguides, sensors, and lasers. WES polymer fibers have an inherent cylindrical geometry similar to that of optical fibers and a relatively large aspect ratio. Furthermore, WES fibers can be produced using low-cost and low-energy manufacturing techniques with large-area fabrication and a large variety of materials. However, the high propagation loss in the fibers, which is normally on the order of tens or thousands of decibels per centimeter in the visible light region, has impeded the use of these fibers in optical fiber devices. Here, the origin of propagation losses is examined to develop a comprehensive and versatile approach to reduce these losses. The excess light scattering that occurs in fibers due to their inhomogeneous density is one of the primary factors in the propagation loss. To reduce this loss, the light transmission characteristics were investigated for single WES polymer fibers heated at different temperatures. The propagation loss was significantly reduced from 17.0 to 8.1 dB cm at 533 nm wavelength, by heating the fibers above their glass transition temperature, 49.8 °C. In addition, systematic verification of the possible loss factors in the fibers confirmed that the propagation loss reduction could be attributed to the reduction of extrinsic excess scattering loss. Heating WES polymer fibers above their glass transition temperature is a versatile approach for reducing the propagation loss and should be applicable to a variety of WES fibers. This finding paves the way for low-loss WES fiber waveguides and their subsequent application in small, flexible optical fiber devices, including waveguides, sensors, and lasers.
湿法静电纺丝（WES）聚合物微米和亚微米纤维是用于制造小型、柔性光纤器件（如波导、传感器和激光器）的有前途的构建材料。WES聚合物纤维具有与光纤相似的固有圆柱形几何形状和相对较大的纵横比。此外，WES纤维可以使用低成本、低能耗的制造技术进行大面积制造，并且可以使用多种材料。然而，这些纤维中的高传播损耗（在可见光区域通常为每厘米数十或数千分贝）阻碍了它们在光纤器件中的应用。在此，研究了传播损耗的起源，以开发一种全面且通用的方法来降低这些损耗。由于纤维密度不均匀而在其中发生的额外光散射是传播损耗的主要因素之一。为了降低这种损耗，研究了在不同温度下加热的单根WES聚合物纤维的光传输特性。通过将纤维加热到其玻璃化转变温度49.8℃以上，在533nm波长下，传播损耗从17.0dB/cm显著降低到8.1dB/cm。此外，对纤维中可能的损耗因素进行的系统验证证实，传播损耗的降低可归因于外在额外散射损耗的降低。将WES聚合物纤维加热到其玻璃化转变温度以上是一种降低传播损耗的通用方法，应该适用于各种WES纤维。这一发现为低损耗WES光纤波导及其随后在小型、柔性光纤器件（包括波导、传感器和激光器）中的应用铺平了道路。
