Rb7SrY2(B5O10)3: A Rare-Earth Pentaborate with Moderate Second-Harmonic Response and Interesting Phase-Matching Behavior.

Phase-matchable (PM) capacity is an indispensable factor in evaluating the applicable prospect of a new nonlinear optical crystal. Obtaining an accurate and credible PM curve by the Kurtz-Perry method using a small single crystal is indeed crucial. Here, we reported a new borate NLO crystal Rb7SrY2(B5O10)3 (I) and studied the influence of the arrangement of micro-[B5O10] groups on its birefringence. Interestingly, the synthesized polycrystalline powder and grinded single crystal display divergent PM and non-PM behavior, respectively. Combining theoretical calculations and analysis, I is demonstrated to be non-phase matchable for the second-harmonic generation (SHG) process of a 1064 nm laser.