Nonlinear LiNbO<sub>3</sub> Local Electric Field Enhancement\nPhotonic Crystal with Static Visible and Dynamic Asymmetric Laser\nProtection

The rapid development of high-energy laser technology\nimposes heightened\nrequirements on multifunctional laser protection. In this article,\nwe report a study of static visible and dynamic asymmetric laser protection\nwindow, utilizing a one-dimensional photonic crystal comprising LiNbO<sub>3</sub> and Nb<sub>2</sub>O<sub>5</sub> defects fabricated by magnetron\nsputtering technique. The visible light transparency and asymmetric\nlaser protection performance are attributed to photonic crystal energy\nband properties and significant local electric field enhancement.\nAs 1064 nm laser energy levels are below 14.44 mJ/cm<sup>2</sup>,\nthe forward and backward incident transmittances are 75.63 and 77.68%,\nrespectively. With an increase in laser energy to 91.62 mJ/cm<sup>2</sup>, the forward and backward transmittances vary to 7.32 and\n71.58% due to the combination of asymmetric electric field enhancement\nand the third-order nonlinear effect of LiNbO<sub>3</sub>, achieving\ndynamic asymmetric laser protection. Notably, the sample exhibits\na lower optical protection threshold of 46.08 mJ/cm<sup>2</sup> compared\nto that of traditional optical protection devices. Furthermore, the\nsample attains an average transmittance of 65.96% within the visible\nlight band. This work presents inspirations for the preparation of\nmultifunctional laser protection optical windows and advanced optical\ncomponents.