Laser crystals from combination paradigm to local structure design: A review on rational design principles, spectroscopic properties and laser applications

Laser crystals have been developed by combination paradigm for more than sixty years, and the methodology is difficult to be continued in uncovering new laser materials. Recently, the local structure design has been proposed and advances have been obtained. This review systematically summarizes the development history of rare earth clusters, cluster structures, evolution characteristics, design principles and the utilization for regulating spectral properties and laser performance of rare earth doped fluorite crystals. We also highlight the future opportunities for development of new laser materials. It is believed that this review will provide valuable insights into rational design principles and new paradigm for development of laser materials. •Exploring new laser crystals with traditional combination paradigm is difficult.•Local structure design is proposed as a new paradigm for laser materials.•Advances of design principles and their utilization for laser crystals were reviewed.•Future opportunities for laser materials development were highlighted.