Computational identification of four promising nonlinear optical materials for near and middle ultraviolet operation

We perform a computational search for promising nonlinear optical materials by screening crystal structure databases. We selected non-centrosymmetric, thermodynamically stable and low-energy metastable borates, with large expected band gaps. For these structures, we performed density functional computations of the gap values, birefringence and nonlinear susceptibilities. Our search revealed four potentially efficient nonlinear borate materials with large band gaps, moderate birefringence and high nonlinear coefficients: K$_3$B$_6$O$_{10}$Cl, Ca$_5$B$_3$O$_9$F, SrB$_4$O$_7$, Al$_4$(B$_2$O$_5$)$_3$.