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承载光通信信号的业务节点处应用可重新配置的光分插复用应用，密集波分复用是当今的主流技术，并且正在增长以扩大每光纤的带宽。平面光波电路平台在这种光网络中起着重要的作用。形成在平面基板上的PLC可以具有诸如复用/解复用、光分支和光切换的各种功能，因此被期望作为实用的光学器件或组件。但是二氧化硅-PLC平台的弱光学限制导致大的组件占用空间以避免相邻通道之间的串扰。深沟不仅具有其他抑制串扰方法所独有的优势，而且还解决了光子电路布局中的大弯曲问题。 支持公司D&T Photonics正在开发PLC VOA（可变光衰减器）和开关，深沟槽将大大提高器件性能并减少占地面积。目前的项目旨在利用光刻、金属剥离和干法等离子体蚀刻定制二氧化硅来制造这种深沟槽。我们的目标是开发一种微加工工艺，以实现可控的沟槽侧壁锥角，最小的侧壁表面粗糙度，和精确控制的沟槽深度。成功后，该技术将转让给支持公司，用于生产PLC VOA和开关。

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.