Two Pyrophosphates with Large Birefringences and Second‐Harmonic Responses as Ultraviolet Nonlinear Optical Materials
Xuefang Lu, Zhaohui Chen, Xuerui Shi, Qun Jing, Ming‐Hsien Lee
Abstract
Abstract Two new pyrophosphates nonlinear optical (NLO) materials, Rb 3 PbBi(P 2 O 7 ) 2 ( I ) and Cs 3 PbBi(P 2 O 7 ) 2 ( II ), were successfully designed and synthesized. Both compounds exhibit large NLO effects and birefringences. Material I presents the scarce case of possessing the coexistence of large birefringence (0.031 at 1064 nm and 0.037 at 532 nm) and second harmonic generation (SHG) response (2.8× potassium dihydrogen phosphate (KDP)) in ultraviolet NLO phosphates and its SHG is the largest in the phase‐matching (PM) pyrophosphates. Both I and II have three‐dimensional (3D) crystal structures composed of corner‐shared RbO 12 (CsO 11 ), RbO 10 (CsO 10 ), BiO 6 , PbO 7 (PbO 6 ) and P 2 O 7 groups, in which P 2 O 7 and PbO 7 (PbO 6 ) units form an alveolate [PbPO] ∞ skeleton frame. Theoretical calculations reveal that the P−O, Bi−O and Pb−O units are mainly responsible for the moderate birefringence and large SHG efficiency of I .