Anti-Reflective Surface structures for Infrared Non-linear Materials

High-power, high-efficiency, broadly-tunable coherent sources in the mid-wave infrared (MWIR, λ=3–5 μm) spectral band are coveted for applications relating to infrared (IR) countermeasures, remote chemical sensing, and free-space optical communication. MWIR sources based on optical nonlinear frequency conversion can generate broadly-tunable kilowatt-level coherent radiation over the entire MWIR spectrum. One factor that limits the source performance is the low optical damage threshold of thin-film anti-reflective coatings applied to the facets of the nonlinear crystal. Anti-reflective surface structures applied to crystal facets have the potential to significantly increase the optical damage threshold given that that the features are monolithically defined in the crystal. However, it is highly-challenging to create these structures on areas as small as a crystal facet. Nanohmics Inc. and the Optical Structured Surfaces Laboratory at the University of North Carolina – Charlotte are working together to develop a lithography-free method of applying random anti-reflective surface structure (rARSS) treatments to nonlinear crystals. The team will demonstrate that its ‘thermodot’-based rARSS technology is a simple and cost-effective method to manufacture broadband (1.5 – 6 micron) AR treatments with superior damage thresholds compared to typical AR thin films.