Nonlinear optical materials based on MBe2BO3F2 (M=Na,K)

MBe2BO3F2 (M=Na,K) have been discovered to be nonlinear optical (NLO) materials for UV applications. They have relatively large NLO coefficients: deff is about 2.5 times as large as that of KH2PO4 (λ=1079 nm, Nd:YAP laser), the UV cutoff wavelengths are as short as 155 nm, and they have a moderate birefringence of nearly 0.10. Their structures are characterized by an infinite sheet which is formed by six-membered rings [Be2BO6F2] with Be-O and B-O edges in common. Such structures are favorable for good NLO properties. These NLO properties make MBe2BO3F2 promising candidates for vacuum UV NLO materials.