A UV solar-blind nonlinear optical crystal with confined & pi;-conjugated groups

UV nonlinear optical (NLO) crystals producing short-wavelength lasers through the second harmonic generation (SHG) process have great significance in the advanced laser field. However, high-performance UV NLO crystals, especially in the UV solar-blind region, are still scarce. In this work, a UV solar-blind NLO compound Rb[PO2(NH)(3)(CO)(2)]& BULL;0.5H(2)O (RPNCO) is obtained through the ion-exchange reaction. Remarkably, the RPNCO compound exhibits an excellent balance within a wide UV transparency window (absorption edge at 220 nm), a strong SHG response (4.2 x KH2PO4), and suitable birefringence (& UDelta;n = 0.055@550 nm). Structural analyses and first-principles calculations reveal that the desirable optical properties of RPNCO are attributed to the confined & pi;-conjugation effect of [PO2(NH)(3)(CO)(2)] asymmetric groups, in which the non-& pi;-conjugated PO2(NH)(2) tetrahedral group partially decouples the & pi;-conjugated interactions. We believe that this research work can help provide new ideas for the rational design of UV solar-blind NLO crystals.