High Refractive Index Sulfur Copolymers for Short-Wave and Mid-Wave Infrared Optics and Photonics

ABSTRACT:The development of organic polymers with high refractive indices and extended transparency in the infrared has been widely investigated, as a possible alternative to inorganic metal oxide, semiconductor, or chalcogenide-based materials for a variety of optical devices and components. In principle, organic-based polymers are attractive for these applications because of their low weight, low cost, ease of processing, mechanical toughness, and facile chemical variation using commercially available precursors. However, one of the fundamental challenges associated with organic polymers is their generally low refractive indices in comparison to their inorganic counterparts, as well as their high infrared absorption owing to the presence of a high concentration of C-H bonds. We propose the development of a new class of sulfur copolymers that are readily moldable, highly transparent from 500nm to 5 microns (alpha 2.0), suitable for many infrared optics applications. These materials will largely be made from elemental sulfur by an inverse vulcanization process, which we have previously demonstrated using a chemically stable, branched copolymer of poly(sulfur-random-1,3-diisopropenylbenzene) (poly(S-r-DIB). We will further build on these initial developments by demonstrating melt and solution processed thin films, windows, and lenses, while extending the platform to demonstrate self-healing.BENEFIT:Existing infrared optical materials are typically bulky semiconductor crystals such as germanium and zinc selenide, or, more recently, chalcogenide glasses which are characterized by difficulty processing and toxicity. The primary defense applications of infrared optical materials include night vision goggles, range finders, LIDAR, and spectroscopy systems, among others. Commercial applications of infrared optical materials include security cameras, gas sensors, and infrared viewers. The emergence of a low-cost, moldable polymer approach to infrared optics in the short-wavelength IR (SWIR) from 0.8 2.5 microns and the mid-wavelength IR (MWIR) from 3 5 microns can fundamentally change both existing products and create entirely new classes of products based on infrared optics. With respect to existing products, the proposed sulfur-based copolymers would enable the creation of much lighter weight night vision goggles, substantially broadening their applications and improving the user experience. The emerging Internet of Things (IoT) would be a welcome a low-cost infrared optical material that could enable a host of new sensor technologies and platforms. Both of these examples are potentially multi-billion dollar opportunities among which others are expected to emerge. It is important to note that the low-cost manufacturing and processing of the initial generation of these materials already establishes the potential for a sustainable long-term advantage that will be extended by successfully completing the proposed work.