Structure Design and Crystal Growth of UV Nonlinear Borate Materials

Crystal design and growth of huntite-type and alkaline beryllium borates used for UV and deep-UV frequency conversion are summarized. A series borates crystallizing in the trigonal-huntite structure, ReM3(BO3)(4) (Re = La, Ga, Y, Lu; M = Y, Lu, Sc, Ga, Al), has been discovered through structural design with respect to the size tuning on trigonal prism or/and octahedral site in the structure. The structural, optical, and chemical-physical properties are detailed. They all have large NLO coefficients, moderate birefringence for UV phase matching, and robust chemical and physical properties. The NLO coefficients of those containing Bi are larger due to the contribution from the lone-pair electron of Bi, while the UV cutoff of these crystals is redshift for about 100 nm. The systematical synthesis of a series of new alkaline beryllium borates with the stoichiometry NaBeB3O6, ABe(2)B(3)O(7) (A = K, Rb), and Na2CsBe6B5O15 in order to obtain deep-UV NLO crystals containing new beryllium borate anionic groups or framework was presented. A new beryllium borate anionic group [Be2B3O11](9-) was found in the structure of NaBeB3O6 and alpha-KBe2B3O7. beta-KBe2B3O7, gamma-KBe2B3O7, RbBe2B3O7, and Na2CsBe6B5O15 consist of 2D alveolate beryllium borate network [Be2BO5](infinity) Furthermore, the adjacent [Be2BO5](infinity) layers in these compounds were connected by covalent bonds.