Shanghai Institute of Optics and Fine Mechanics has made significant breakthroughs in the study of laser damage performance of mid infrared anti reflective coatings

Recently, the Thin Film Optics Research and Development Center of the High Power Laser Component Technology and Engineering Department of the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, collaborated with researchers from Hunan University and Shanghai University of Technology to make new progress in the study of laser damage performance of mid infrared anti reflective coatings. The research team has developed a 6-layer mid infrared double-sided anti reflective film based on HfO2/SiO2 material on a quartz substrate by optimizing the preparation process, with a laser-induced damage threshold (LIDT) of 91.91 J/cm;. The related achievements were published in Infrared Physics&Technology under the title "The performance of laser induced damage of a 2-4 μ m mid frared anti reflective coating based on HfO2/SiO2 materials".

The surface reflection loss of infrared optical components is significant, and anti reflective films have become the key to improving device efficiency. Traditional infrared anti reflective film materials (such as fluoride and sulfide) have problems such as insufficient stability and easy water absorption, while oxide materials (such as HfO2/SiO2) have become a research hotspot due to their high melting point, high environmental stability, and high LIDT.

Figure 1 (a) Transmittance of the anti reflective film (b) Reflectance of the anti reflective film (c) LIDT test of the anti reflective film

A 6-layer HfO2/SiO2 film system structure with a total thickness of 2180nm was designed using electron beam evaporation (EB) and ion assisted deposition (EB-IAD) techniques. By comparing the two processes, it was found that ion assisted technology significantly optimized the quality of the film layer, and the EB-IAD process prepared the film layer with higher crystallinity, lower surface roughness, and significantly reduced water absorption. The laser damage threshold is increased, and the LIDT of EB-IAD anti reflective film under 2.097 μ m laser reaches 91.91 J/cm2, while the EB process only achieves 11.25 J/cm;. After analyzing the damage morphology, it was found that the EB anti reflective film was affected by the nanosecond thermal effect, resulting in larger and deeper damage points. The EB-IAD film layer was mainly ablated by plasma, with a smaller damage area and stronger interfacial adhesion. This study provides theoretical basis and process reference for the design and preparation of mid infrared anti reflective films. The research results are expected to be applied to the mid infrared nonlinear crystal ZnGeP2 and more mid infrared laser systems besides ZnGeP2 crystals, such as high-power laser processing, infrared imaging, optical communication and other fields, promoting the development of related industries.

Source: opticsky