New nonlinear optical crystal K2Al2B2O7

The new nonlinear optical crystal K2Al2B2O7 is discovered with the molecula r engineering approach on the basis of anionic group theory. An optically p erfect single crystal with space group P321, free of moisture and hygroscop y, is readily grown by the top-seeding flux method. Its transparence range covers 180 to 3600 nm. The refractive indices are measured with the minimum -deviation method, based on which the Sellmeier equation is obtained. The m easured nonlinear optical coefficient d(11) is 0.45 pm/V. The moderate walk -off angle and angular bandwidth, together with the high optical homogeneit y, make it a promising candidate for the fourth- and the fifth-harmonic gen eration of a Nd:YAG laser. (C) 2000 Optical Society of America [S0740-3224( 00)02704-1]. OCIS codes: 160.4330, 190.4400.