The present invention provides a compound having the chemical formula of R.sub.2 MB.sub.10 O.sub.19, wherein R is one or more elements selected from the group consisting of rare-earth elements or Y; M is selected from the group consisting of Ca, Sr, Ba, a single crystal of the compound, a producing method and uses thereof. The compound is congruently melting, which is suitable for producing large size single crystal of R.sub.2 MB.sub.10 O.sub.19 with melt methods, especially pulling method, at a low cost. The crystal resulted therefrom has the same NLO effect as LBO with superior mechanical properties, and it is antideliquenscent. The crystal of the present invention can be used for the frequency-conversion of blue-green wavelength lasers.
The present invention relates to nonlinear optical crystals of compound Na.sub.3 La.sub.9 B.sub.8 O.sub.27 and producing method and uses thereof. From the Na.sub.3 La.sub.9 B.sub.8 O.sub.27 compound, large size single crystal of Na.sub.3 La.sub.9 B.sub.8 O.sub.27 could be prepared by flux method. Na.sub.3 La.sub.9 B.sub.8 O.sub.27 crystals are non-hygroscopic, and possess stronger nonlinear optical effect and good mechanical properties. They meet the requirements for the frequency conversion of blue--green wavelength lasers and could be used to prepare nonlinear optical devices.
A material for harmonic generation has been made by substitutional changes to the crystal LaCa.sub.4 (BO.sub.3).sub.3 also known as LaCOB in the form Re1.sub.xRe2.sub.yRe3.sub.zCa.sub.4(B0.sub.3).sub.3O where Re1 and Re2, (rare earth ion 1 and rare earth ion 2) are selected from the group consisting of Sc, Yttrium, La, Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, and Lu; Re3 is Lanthanum; and x+y+z=1.
