Microstructure-Based Anti-Reflection Treatment for Long-Wave Infrared Transmitting Optical Fiber

The DOE requires a new class of long wave infrared (LWIR) transmitting optical fiber for the remote detection of signatures associated with weapons of mass destruction. Unfortunately, issues abound with the traditional thin film type coatings for LWIR. These coating issues include limited optical performance over narrow bandwidths, low threshold for damage from high power laser sources, and poor uniformity when applied to curved surfaces or fiber end faces. In addition, a relatively new class of IR transmitting chalcogenide based glasses is being developed with high indexes of refraction that cause a total of 30% to 40% reflection loss from both fiber exit faces. In order to optimize transmission, these glasses will require an anti-reflective (AR) treatment. This project will demonstrate a process to apply a high performance, broad band (8-12 micron), high-damage-threshold AR treatment of LWIR transmitting fiber. Phase I will demonstrate that the AR microstructure treatment provides a significant increase in transmitted light at power levels two times higher than the threshold for damage in current fiber lasers. Commercial Applications and other Benefits as described by the awardee The use of the AR microstructure technology in quantum cascade lasers should provide a significant performance increase leading to improved detection ranges in remote sensing systems. Beyond detection systems for defense and security, the technology would enable the further development and miniaturization of quantum cascade lasers for biomedical analysis, chemical analysis, pollution monitoring, and free space communication