Low-Transmission-Loss Optical Waveguide Devices of Polyimides with Trifluoromethoxy-Enhanced Ultrahigh Refractive Index for Short-Distance Optical Communication

Short-distance optical communication technology has been promoted to a crucial position with the rapid development of network systems centered around data, which inevitably leads to the urgency of developing a high-performance optical transmission medium. To address these requirements, several ternary copolymerized polyimides, known as high-performance engineering plastics, are developed through the most common two-step thermal imidization strategy. The introduction of trifluoromethoxy (−OCF3) groups provides polymers with an ultrahigh refractive index above 1.8 under the common observation conditions of communication wavelengths, as well as an ultralow birefringence of 0.003. More importantly, under the chief band of optical fiber communication at 1310 and 1550 nm, generated by modulated lasers, these polymers show very weak light absorption and signal attenuation behaviors, thereby demonstrating huge potential in the field of optical waveguide device development. Additionally, considering the extremely low moisture absorption of the polymers, these transparent polyimides with high refractive index are expected to be fundamental material candidates in many fields, such as optical communication, the Internet of Things, 5G transmission, and other advanced technologies in extreme environments.