Optimized oxygen plasma etching of polycarbonate for low-loss optical waveguide fabrication

The oxygen plasma etching condition of polycarbonate was characterized in detail to fabricate low-loss optical waveguides. The effects of etching parameters such as rf power and chamber pressure were systematically studied and the parameters were optimized to minimize the surface roughness in etched areas. Buried channel waveguides with thermally stable polycarbonate were fabricated using the optimized conditions, resulting in smooth and almost vertical etched patterns. The waveguides showed an optical loss of less than 0.8 dB/cm and 1.4 dB/cm at the wavelength of 1.3 μm for TE and TM polarizations, respectively. The refractive index of polycarbonate after being stored at 190-230°C for 1 h remains almost constant, demonstrating the thermal stability of polycarbonate waveguides.