Crystal growth and efficient second-harmonic generation of quasi one-dimensional centrosymmetric KDP single-crystalline microstructures

International Conference on Applied Crystallography

October 17-19, 2016 Houston, USA

Yan Ren

Shandong University, China

Posters & Accepted Abstracts: J Material Sci Eng

Abstract :

Potassium di-hydrogen phosphate (KH2PO4 or KDP) single crystals are important multifunctional crystals, which possess distinct piezoelectric, ferroelectric, electro-optic and second-harmonic generation (SHG) properties. In the past a few decades, studies on KDP crystals mainly focused on the large-size and high optical quality tetragonal phase KDP crystals in order to satisfy the demand for nonlinear and electro-optic applications in laser inertial confinement fusion. However, low-dimensional, self-assembled KDP microstructures and their important nonlinear optical properties have been largely overlooked. In this work, we reported the ambientcondition growth of high optical quality KDP microstructures with large length-to-diameter ratio. The exact X-ray diffraction date indicates that the microstructures possess identical crystal structure with the centrosymmetric high pressure IV phase of KDP, which was never known to crystallize under ambient conditions. However, Laue diffraction also showed the presence of a very small fraction of twin crystal lattice on (hk0) plane of the microstructure. According to the fundamental physics, SHG is strictly forbidden in crystals possessing perfect centrosymmetric properties. However, we observed a highly efficient optical SHG in the centrosymmetric KDP microstructures. The normalized conversion efficiency of 532 nm light is up to 10-4 W-1 pumped by 1-W CW light at 1064 nm. We explained that the SHG is attributing to the small fraction of twin-crystal-induced symmetry breaking (although possibilities of other weak-symmetry-breaking mechanisms cannot be completely eliminated). Using these microstructures, we also demonstrated the polarization-maintaining features of the KDP microstructures, which can be exploited for advanced optical communication applications.

Biography :

Email: ry@sdu.edu.cn