Optically transparent fluorine-containing polycarbonates with high refractive indices for thermo-optic switches†
In this paper, we report the design, synthesis, and optical properties of novel negative-type fluorinated polycarbonate photoresists (FPC-PRs) and their use in thermo-optic switches. The novel polymer films are readily fabricated by spin coating on a silicon wafer followed by irradiation with UV light and post-baking at 110 °C. These films exhibit low roughness, good thermal stability (Td, up to 292 °C), high transparency (up to 97.8% at 400 nm) and high refractive indices (RI, 1.583–1.512 at 1550 nm). Channel optical waveguide and MZI thermo-optic waveguide switch arrays were fabricated based on the direct UV-written technique using the FPC-PR 2. The propagation loss of the channel waveguide was only 0.17 dB cm−1 at 1550 nm. The rise and fall times of the device with an applied 500 Hz square-wave voltage were 837 μs and 381.8 μs, respectively. The applied electric power as the switching power was about 35 mW, and the extinction ratio was measured to be about 14.0 dB.