Synthesis of Siloxane-polyimide Copolymer with Low Birefringence and Low Loss for Optical Waveguide

Optical properties of fluorinated polysiloxane-co-polyimide (PI-ATPDMS) were investigated based on the molecular structure and compared with the pure polyimide (PI) at 1550 nm radiation. The refractive index of the copolymers was slightly reduced by 3.5% whilst the birefringence was reduced by 0.37% respectively compared to PI. They are highly transparent at near infrared (IR) region with light transmittance above 90% at visible region. An asymmetry planar waveguide was fabricated which recorded a respectable low optical loss o f0.020 dB cm-1 for pure PI and 0.042 dB cm-1 for PI-ATPDMS, respectively. The excellent optical properties displayed by these series of materials established their viable application as waveguide material at 1550 nm wavelength.