Laser Direct Writing of Single-Mode Polysiloxane Optical Waveguides and Devices

Using a custom-built laser direct writing system, single-mode polymer optical waveguides, and devices for board-level optical interconnects were fabricated. A novel photopatternable polysiloxane material was developed that combines low-loss, simple, and large-area processability, and reliability during manufacturing and system operation. The polysiloxane waveguides were designed with quadratic cross sections of 5.5 × 5.5 μm
²
and a refractive index contrast of 0.0086 between core and cladding polymer for single-mode operation at the wavelength of 1.3 μm. A straight waveguide propagation loss of 0.28 dB/cm was achieved. A wide range of passive optical devices, including Y-splitters, directional couplers, and Mach-Zehnder interferometers were successfully fabricated and characterized. The results prove that the presented combination of material and process technology is a viable implementation for short distance board-level optical links.