title: Crystal growth and optical characteristics of beryllium-free polyphosphate, KLa(PO3)4, a possible deep-ultraviolet nonlinear optical crystal.
abstract: Deep-ultraviolet nonlinear optical crystals are of great importance as key materials in generating coherent light with wavelength below 200 nm through cascaded frequency conversion of solid-state lasers. However, the solely usable crystal in practice, KBe2BO3F2 (KBBF), is still commercially unavailable because of the high toxicity of beryllium-containing and the extreme difficulty of crystal growth. Here, we report the crystal growth and characteristics of an beryllium-free polyphosphate, KLa(PO3)4. Centimeter-sized single crystals have been easily obtained by the flux method and slow-cooling technique. The second-harmonic generation efficiency of KLa(PO3)4 powder is 0.7 times that of KH2PO4; moreover, the KLa(PO3)4 crystal is phase-matchable. Remarkably, the KLa(PO3)4 crystal exhibits an absorption edge of 162 nm, which is the shortest among phase-matchable phosphates so far. These attributes make KLa(PO3)4 a possible deep-ultraviolet nonlinear optical crystal. An analysis of the dipole moments of the polyhedra and theoretical calculations by density functional theory were made to elucidate the structure-properties relationships of KLa(PO3)4.
authors.affiliation: The MOE Key Laboratory of Weak-Light Nonlinear Photonics and School of Physics, Nankai University, Tianjin 300071, China.
authors.forename: Pai
authors.initials: P
authors.lastname: Shan
authors.affiliation: The MOE Key Laboratory of Weak-Light Nonlinear Photonics and School of Physics, Nankai University, Tianjin 300071, China.|Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China.
authors.forename: Tongqing
authors.initials: T
authors.lastname: Sun
authors.affiliation: The MOE Key Laboratory of Weak-Light Nonlinear Photonics and School of Physics, Nankai University, Tianjin 300071, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Chen
authors.affiliation: The MOE Key Laboratory of Weak-Light Nonlinear Photonics and School of Physics, Nankai University, Tianjin 300071, China.|Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China.
authors.forename: Hongde
authors.initials: H
authors.lastname: Liu
authors.affiliation: The MOE Key Laboratory of Weak-Light Nonlinear Photonics and School of Physics, Nankai University, Tianjin 300071, China.|Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China.|Teda Institute of Applied Physics, Nankai University, Tianjin 300457, China.
authors.forename: Shaolin
authors.initials: S
authors.lastname: Chen
authors.affiliation: School of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004, China.
authors.forename: Xuanwen
authors.initials: X
authors.lastname: Liu
authors.affiliation: The MOE Key Laboratory of Weak-Light Nonlinear Photonics and School of Physics, Nankai University, Tianjin 300071, China.|Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China.|Teda Institute of Applied Physics, Nankai University, Tianjin 300457, China.
authors.forename: Yongfa
authors.initials: Y
authors.lastname: Kong
authors.affiliation: The MOE Key Laboratory of Weak-Light Nonlinear Photonics and School of Physics, Nankai University, Tianjin 300071, China.|Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China.|Teda Institute of Applied Physics, Nankai University, Tianjin 300457, China.
authors.forename: Jingjun
authors.initials: J
authors.lastname: Xu