Novel fluorinated polycarbonate negative-type photoresists for thermo-optic waveguide gate switch arrays
A series of novel thermo-optic (TO) polymers (AF-Z-PC EPs) were achieved and they could be mixed with photoinitiator in solvent and to produce the negative-type fluorinated photoresists (NFPRs). TO waveguide switch arrays were fabricated based on the direct UV-written technique using the NFPRs. As the core of waveguide materials, AF-Z-PC EPs were synthesized by solution polymerization with 4,4′-(hexafluoro-isopropylidene) diphenol (6F-BPA) and bisphenol Z (BPZ) with triphosgene (BTC) and further reacted with epoxy chloropropane. The refractive index of the polymers can be adjusted by controlling the content of BPZ. Through a simple lithography process, the NFPRs can be fabricated as the waveguide easily. The propagation loss of a 4 μm wide straight waveguide was only 0.19 dB cm−1 at 1550 nm. The insertion loss of the device was directly measured to be about 9.0 dB. The rise and fall times of the device applied 200 Hz square-wave voltage were obtained as 1.546 ms and 1.226 ms, respectively. The switching power was about 15.5 mW, and the extinction ratio was 13.0 dB. The low-loss integrated switch arrays are suitable for realizing large-scale photonic integrated circuits.