Calculation of nonlinear optical crystal CaB5O7F3 based on first-principles

Deep ultraviolet laser (wavelength less than 200nm) has a wide range of applications in laser medical, material microprocessing, laser lithography, and other cutting-edge laser technology. The nonlinear optical crystal can transform the frequency of the common band laser and produce deep ultraviolet light, which is the focus of the current laser technology research. However, the growth of crystals is time-consuming and labor-consuming. Even if some crystals are grown, their properties may not be satisfactory. In the past decade, thanks to the development of high-performance computers, the computational research scheme based on the first-principles simulation has been developed, which promotes the development of deep UV NLO crystals and guides the follow-up and further experimental exploration. At present, some mature nonlinear crystals such as BBO, CLBO, and LBO can generate deep UV lasers by nonlinear frequency conversion, but their performance is not as good as KBBF. In this paper, the band gap, band structure, and optical properties of CaB5O7F3 in the KBBF family are calculated by the first-principles theory.