Innovative high-performance nanowire-grid polarizers and integrated isolators

摘要

We developed a new type of wire-grid polarizer, the so-called nanowire-grid polarizer, which has achieved commercial quality optical performance and reliability. The nanowire-grid polarizer has cores composed of silicon dioxide nanowalls with metal coating on one side. These cores are surrounded by multilayer thin films for antireflection. The core nanowire grid utilizes nano-sized high-aspect ratio dielectric walls as a support for forming a high aspect ratio metal nanowire grid, which significantly reduces energy loss due to metal absorption for the transmitted beam while achieving high extinction ratio for the blocked beam. For all design simulations, we utilized a rigorous coupled-wave analysis and modal method. The nanowire-grid structure was fabricated by a wafer-based nanoreplication lithography and pattern-transfer techniques, which are capable of producing a large-area high aspect ratio nanostructure with high throughput and low cost. The optical performance of the nanowire-grid polarizer was characterized thoroughly. Furthermore, the nanowire-grid polarizer has been integrated monolithically with a Faraday magnetooptic garnet, which results in an integrated semi-isolator. Full free-space isolators based on the integrated semi-isolators have been also developed, which achieved excellent performance, good enough for commercial applications.