Finding the Next Deep-Ultraviolet Nonlinear Optical Material: NH₄B₄O₆F

Nonlinear optical materials are essential for the development of solid-state lasers. KBe₂BO₃F₂ (KBBF) is a unique nonlinear optical material for generation of deep-ultraviolet coherent light; however, its industrial application is limited. Here, we report a new material NH₄B₄O₆F, which exhibits a wide deep-ultraviolet transparent range and suitable birefringence that enables frequency doubling below 200 nm. NH₄B₄O₆F possesses large nonlinear coefficients about 2.5 times that of KBBF. In addition, it is easy to grow bulk crystals and does not contain toxic elements.