Recently, researchers from the Shanghai Institute of Optics and Fine Mechanics of the Chinese Academy of Sciences has made new progress in the research of high-threshold broadband low-dispersion mirrors. Based on the damage mechanism of metal-dielectric low dispersion mirror (MLDM), they used interface enhancement technology to increase the damage threshold by 22%. Related research results have been published on Optics Express on Mar.15, 2021. 

Low dispersion mirror is one of the most important components in the ultrashort ultrahigh intensity laser systems. With the development of ultrashort ultrahigh intensity laser, the pulse width has been compressed to several femtoseconds, which puts forward new requirements for reflective elements in laser systems: high damage threshold, wide bandwidth, and high reflectivity, and does not introduce additional dispersion. 

The researchers studied the MLDM and found that the initial damage source of the MLDM under the action of femtosecond laser was located at the interface, and the overall damage morphology showed stress failure.

Finite element analysis shows that the interface is in a strong stress field. The thermal annealing process promotes the diffusion of atoms at the interface, the bonding force at the interface is enhanced, the damage source is transferred from the interface to the surface, and the damage threshold is increased by 22%. 

They expect to provide a new idea for improving the damage resistance of MLDMs by this research. 

This work was supported by the National Key Research & Development Program of China, and the National Natural Science Foundation of China. 

Fig. 2. (a) Enlarged view of the damage center area; (b) Surface damage morphology after interface enhancement; (c) section morphology of the damage boundary. (Image by SIOM)