Erbium-doped polymer waveguide amplifiers for PCB-integrated optical links

Optical technologies are increasingly considered for use inside high-performance electronic systems to overcome the performance bottleneck of electrical interconnects when operating at high frequencies and provide high-speed communication between electronic chips and modules. Polymer waveguides are a leading candidate to implement board-level optical interconnections as they exhibit favourable mechanical, thermal and optical properties for direct integration onto conventional printed circuit boards (PCBs). Numerous system demonstrators have been reported in recent years featuring different types of polymer materials and opto-electronic (OE) PCB designs. However, all demonstrated polymer-based interconnection technologies are currently passive, which limits the length of the on-board links and the number of components that can be connected in optical bus architectures. In this paper therefore, we present work towards the formation of low-cost optical waveguide amplifiers that can be readily integrated onto standard PCBs by combining two promising optical technologies: siloxane-based polymer waveguides and ultra-fast laser plasma implantation (ULPI). Siloxane-based waveguides exhibit high-temperature resistance in excess of 300°C and low loss at different wavelength ranges, while ULPI has been demonstrated to produce very high dopant concentrations in thin films with values of 1.63×1021 cm−3 recently reported in Er-doped silica layers. Here we present detailed simulation studies that demonstrate the potential to achieve a net gain of up to 8 dB/cm from such structures and report on initial experimental work on Er-doped polymer films and waveguides demonstrating photoluminescence and good lifetimes.