Synthesis of liquid polysilisiquioxane resins and properties of cured films

Two kinds of UV-patternable liquid polysilisiquioxane (PSQ) resins (one was named as PSQ-L152 and the refractive index of its cured film was 1.5212 at 1310 nm, the other was named as PSQ-L145 and the refractive index of its cured film was 1.4483 at 1310 nm) have been synthesized by alternative sol–gel process for waveguide application. Chemical structures of the two resins were characterised by Fourier-transformed infrared spectroscopy (FTIR) and 29Si nuclear magnetic resonance technique. And the hybrid curing processes were also investigated by FTIR, and discussed the dependence of optical loss on thermal curing temperature and time. In addition, refractive indices of the films can be exactly tuned from 1.4483 to 1.5212 and optical losses of the PSQ-L152 film were about 0.2 dB·cm− 1 at 1310 nm, 0.7 dB·cm− 1 at 1550 nm, respectively. Furthermore, the films also showed low surface roughness and outstanding thermal stability both in nitrogen and air atmospheres.