3D optical waveguides produced by two photon photopolymerisation of a flexible silanol terminated polysiloxane containing acrylate functional groups

Optical waveguides are becoming increasingly important in the developing area of broadband communications. The field of electronics is advancing rapidly, leading to further demands for larger data storage, smaller components and a better design of integrated optical circuits. The integration of optical interconnects on printed circuit boards (PCBs) requires precise technologies to make this emerging field possible. A promising new microfabrication technique, two-photon photopolymerisation (2PP) can be used to produce three dimensional structures in the sub-micron region. Near-infrared lasers can be used to create 3D optical waveguides by initiating the photopolymerisation of high refractive index monomers in polymeric matrix materials. Terminal silanol groups are intermediates for room temperature vulcaniseable (RTV) silicones and can be cross linked with functional silanes to produce flexible, transparent polymeric materials with high thermal stabilities. A silanol terminated polysiloxane; cross linked with a methyl substituted acryloxy silane has been developed as a suitable material for the fabrication of optical waveguides by two-photon absorption (TPA). A higher refractive index is achieved upon polymerisation of the acrylate functional groups. The material has been shown to be suitable in the fabrication of 3D optical waveguides with a high refractive index contrast. The cured material is fully flexible and exhibits high thermal stability and optical transparency. The material was characterised by Fourier transform infrared spectroscopy (FT-IR), simultaneous thermal analysis coupled with mass spectrometry (STA-MS) and near-infrared spectroscopy (NIRS). Waveguides were observed by phase contrast microscopy, cut back measurements and were additionally directly integrated onto specially designed PCBs by correctly positioning waveguide bundles between optoelectronic components using TPA.