Laser Protection Properties of Multi-Band Non-Regularized Highly Reflective Films

With the increasing exploitation of lasers, single-band laser protection has been extensively studied. However, single-band laser protection techniques have remained expensive and failed to meet protection requirements for multi-band lasers. In addition, the actual use of protective films requires a specific transmittance, which is generally not met by regular films. Here, we deposited three non-regularized highly reflective films using SiO2 as the low-refractive-index material and TiO2, HfO2, and Ta2O5 as the high-refractive-index materials by thermal evaporation for achieving multi-band laser protection. To verify the effectiveness of the films, the variation in transmittance, damage threshold, standing-wave electric field, and damage morphology of the films were analyzed at two laser wavelengths, and their protection mechanisms were evaluated based on optical properties and damage resistance. The results showed that the reflectances of the prepared non-regularized films at 1064 nm and 532 nm were greater than 99%, and the laser-induced damage thresholds for TiO2/SiO2, HfO2/SiO2, and Ta2O5/SiO2 films were 5.99, 5.89, and 9.99 J/cm2 at 1064 nm and 3.04 J/cm2, 1.48 J/cm2, and 4.93 J/cm2 at 532 nm, respectively, demonstrating good laser protection. The present work provides a practical and effective solution for multi-band laser protection and the prepared films may be used in numerous laser applications.