A novel lightwave device integration and coupling process for optical interconnects

Optical interconnects technology is considered by many researchers and system engineers as the next paradigm shift in data transport technology within a shelf of line cards or data processing boards. A continuing challenge over the past ten years has been the integration process of the laser, detector and waveguide. A major difficulty of this integration process is the optical alignment of these three components which is exacerbated by the fact that both a VCSEL and a standard PIN PD are surface emitting and surface viewing devices, respectively, while waveguides are generally fabricated parallel to the surface of the substrate. Power losses occur for different reasons in the electrical and optical domain. Power losses in the electrical domain are mainly due to the distance traveled, while the power loss in the optical domain is mostly due to light guiding (reflecting, bending, etc.). Choosing an architecture that benefits of the metal medium´s advantages and the optical medium´s advantages will yield a better channel. In the proposed approach the VCSEL and PIN PD are side-mounted on a sub-anchor board so that the light emission and viewing directions are both in the plane of the substrate. A liquid, photo-definable monomer is placed between the two O/E components and forms a monomer-component interface. Polymerization of the monomer film between VCSEL and PIN PD is initiated with a stripe of UV light defined by a glass mask. By inserting a small distance in the electrical domain such that the light emission, light viewing and waveguide are in the same plane eliminates the need for 45deg mirrors, or alternate bending methods, and reduces the overall loss of the optical channel. In addition, the process is simple and inexpensive, making it appealing to access (and other mass produced) networking products for home and in-building communications systems. We have designed, integrated and tested prototype devices using this process. Preliminary experimental results sho- w an average coupling efficiency of 20% and crosstalk of < 27 dB.