Structure-property relationship of fluorinated co-poly(arylene ether sulfide)s and co-poly(arylene ether sulfone)s for low-loss and low-birefringence waveguide devices

Optical properties such as refractive index, birefringence, thermal stability, and optical loss of fluorinated co-poly(arylene ether sulfide)s and co-poly(arylene ether sulfone)s were investigated, and they are related to the molecular structure of the polymers. The refractive index of the optical polymers varies in the range of 1.51∼1.60, and its variation is well described by a Lorentz-Lorenz equation. Their birefringence varies between 0.0027∼0.0039 for the sulfides series and between 0.0009∼0.0025 for the sulfone series at a 1.55-μm wavelength, respectively. The birefringence is analyzed based on the microscopic anisotropic ratio of the polarizability of the molecular repeating unit resulting in good linear relationship between them within the polymer groups. This result implies that the molecular calculation can be utilized to design polymers with low birefringence. The propagation losses of the optical polymers were 0.1∼0.3 and 0.2∼0.5 dB/cm at the wavelength of 1.3 and 1.55 μm, respectively. The optical losses are inversely proportional to fluorine content. The polymers have good thermal stability upon long-term thermal stress at 100 °C for 1000 h and short-term thermal stress at 300 °C for 1 h.