Bioinspired Near-Full Transmittance MgF2 Window for Infrared Detection in Extremely Complex Environments

Due to the extreme complexity of the anti-reflectivesubwavelengthstructure (ASS) parameters and the drastic limitation of Gaussianbeam manufacturing accuracy, it remains a great challenge to manufactureASS with ultrahigh transmittance on the surface of infrared windowmaterials (such as magnesium fluoride (MgF2)) directlyby femtosecond laser. Here, a design, manufacturing, and characterizationmethod that can produce an ultrahigh-performance infrared window byfemtosecond laser Bessel beam is proposed. Inspired by the excellentanti-reflective and hydrophobic properties of the special structureof dragonfly wings, a similar structural pattern with grid-distributedtruncated cones is designed and optimized for its corresponding parametersto achieve near-full transmittance. The desired submicron structuresare successfully fabricated by a Bessel beam after effectively shapingthe beam. As a practical application, the bioinspired ASS is manufacturedon the surface of MgF2, achieving an ultrahigh transmittanceof 99.896% in the broadband of 3-5 mu m, ultrawide angleof incidence (over 70% at 75 degrees incidence), and good hydrophobicitywith a water contact angle of 99.805 degrees. Results from infraredthermal imaging experiments show that the ultrahigh-transmittanceMgF(2) window has superior image acquisition and anti-interferenceperformance (3.9-8.6% image contrast enhancement and more accurateimage edge recognition) in an environment with multiple interferingfactors, which may play a significant role in facilitating applicationsof infrared thermal imaging technologies in extremely complex environments.