CO2 laser micromachining of optical waveguides for interconnection on circuit boards

The introduction of microvia and surface mount technologies into the manufacturing process for printed circuit boards (PCBs) has significantly improved the interconnection density. However, as the speed of signals for data communication on the board approaches and begins to exceed 10 Gb/s, the loss and crosstalk of copper interconnections increase. To resolve these problems, optical interconnections (OI) have been suggested as a viable solution. Literature reports have proved the photochemical nature of excimer laser ablation with its minimal thermal effect, and other ultra-violet lasers are also being investigated for the fabrication of polymer waveguides by laser ablation. In this paper, the authors demonstrate the fabrication of multimode optical polymer waveguides by using infra-red 10.6 μm CO2 laser micromachining to etch acrylate-based photopolymer (Truemode™). CO2 lasers offer a low cost and high speed fabrication route as CO2 lasers can be used to cut through various engineering materials including polymers and metals. The paper characterises the relationship between the laser ablation power, the fabrication speed and the resulting effect on the waveguide optical insertion loss for the first time.