Chalcogenide-based Mid-Infrared High-Efficiency Broadband Diffraction Gratings

Development of ultra-short pulse laser (USPL) system operating in the mid-infrared (MIR) region is an important priority towards the advancement of Directed Energy (DE) applications within the US military. However, to realize the MIR USPL system for DE applications, there is a need to achieve a laser pulse compression below 100 femtoseconds for a laser > 10 mJ power in the 3-5 µm frequency range. This can be accomplished with a broadband diffraction grating with high efficiency in the MIR frequencies, however such gratings are yet to be demonstrated successfully on a manufacturing scale. This is attributed to lack of reliable fabrication technique using the material systems suitable for MIR frequency range. RMD Inc. proposes to address this problem by exploring the design, fabrication, and manufacturability of a special class of broadband high-efficiency diffraction gratings based on metasurfaces- hereafter referred to as “metagratings”. A critical innovation that will enable metagratings for the MIR frequency is the use of high refractive index / low absorption lead cadmium telluride (Pb1-xCdxTe) alloy. Our choices of the material, device design and processing route are uniquely defined by the performance targets specified in the call and present a technical solution that can scaled to other wavelengths, device architectures, and optical functions.