High precision fabrication of deep trenches for photonic communication chips

在光纤网络中，客户将在使用密集波分复用的承载光通信信号的交通节点上应用可重新配置的光添加/丢弃多路复用应用，这是当今的主流技术，并且正在扩大每根光纤的带宽。平面光波电路（PLC）平台在这种光子网络中起着重要的作用。在平面基板上形成的PLC可以具有多种功能，例如多路复用/解路复用、光分支和光交换，因此有望作为实用的光学器件或组件。但硅- plc平台的弱光约束导致元件占用较大，以避免相邻通道之间的串扰。深沟槽不仅具有抑制串扰的独特优势，而且解决了光子电路布局中的大弯曲问题。

In fiber optic networks, customers will apply the re-configurable optical add/drop multiplexing application at traffic nodes carrying optical communication signals using dense wavelength division multiplexing, which is the incumbent technique today and is growing to scale up bandwidth per fiber. Planar lightwave circuit (PLC) platform plays important roles in such photonic network. A PLC formed on a planar substrate can have various functions such as multiplexing/demultiplexing, optical branching, and optical switching, and hence is expected as a practical optical device or component. But weak optical confinement of silica-PLC platform leads to large component footprints to avoid cross-talk between adjacent channels. Deep trenching not only holds its exclusive advantages over other approaches to suppress the cross-talk, but also solves the large bending problem in photonic circuit layouts. The supporting company D&T Photonics is developing PLC VOA (variable optical attenuators) and switches, for which deep trenching would greatly enhance the device performance and reduce the footprint. The current project aims to fabricate such deep trenches using photo-lithography, metal liftoff and dry plasma etching of custom-made silica. The goal is to develop a microfabrication process to achieve controllable trench sidewall taper angle, minimum sidewall surface roughness, and precise control of trench depth. With success, the technology will be transferred to the supporting company for their production of PLC VOA and switches.