Research conducted in Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science (HFIPS), Chinese Academy of Sciences (CAS) described the damage mechanism of CaF₂ crystal, an important component in the ultra­violet optical system, and concluded that it’s closely related to cleavage plane and sliding system. The team, led by Liang Xu and Shao Jingzhen, studied the laser-induced damage charac­teristics with a self-deve­loped KrF excimer laser, and analyzed the formation mechanism of surface morphology of three different crystal planes.

“We studied the cleavage plane {111}, the slip system {100}〈110〉, the angular relation­ship between the crystal plane, the slip system and cleavage plane,” explained Shao, “and found it's the structural characteristics of the CaF₂ crystal that led to the different mechanical properties on different crystal planes.” CaF₂ crystal directly affects the stability and life of UV optical system. There­fore, scientists have turned their attention to the process and mechanism of the inter­action between UV laser and the CaF₂ crystal to improve its laser damage resistance.

In this research, scientists completed laser irra­diation experiment on CaF₂ crystal with this 248 nanometer excimer laser. They obtained the evolution of damage morphology and the laser induced damage thresholds of three different CaF₂ crystals planes (100), (110) and (111). The results displayed different damage morpho­logy.

The damage of plane (111) showed the pheno­menon of lamellar stripped, while there was a burst-like damage on plane (110) and plane (100), which originated from the crack or local damage point. These results pave the way for the appli­cation of CaF₂ crystals with different crystal planes in UV laser system. (Source: CAS)

Reference: J. Shao et al.: KrF excimer laser induced damage and its mechanism of CaF₂ single crystal with (1 1 1), (1 1 0) and (1 0 0) planes, Appl. Surf. Sc. 586, 152716 (2022); DOI: 10.1016/j.apsusc.2022.152716

Link: Anhui Provincial Key Laboratory of Photonics Devices and Materials, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China