Growth and optical properties of K2(Al0.71Ga0.29)2B2O7 crystal

• Crystal of K2(Al0.71Ga0.29)2B2O7 (KAGBO) has been grown.
• The crystal structure of KAGBO crystal is determined.
• Sellmeier equations were obtained from measured refractive indices.
• KAGBO crystal is capable of fourth harmonic generation of Nd-lasers.

Crystals of K2(Al0.71Ga0.29)2B2O7 (KAGBO) with dimensions up to 20 × 15 × 10 mm3 have been grown with NaF flux by the top-seeded solution growth method. The structure of KAGBO crystal is analog to its parent compound K2Al2B2O7 and belongs to the space group P321 with cell parameters of a = 8.5700(12) Å and c = 8.524(3) Å. Both theoretical calculation based on the structure and powder second-harmonic generation (SHG) test reveal that KAGBO has a slight smaller SHG coefficient d11 as that of KABO or KH2PO4 (KDP). KAGBO crystal also shows a wide transparency range from 189 to 3000 nm and its measured refractive indices indicate that KAGBO can be phase matched to 234.7 nm for type I SHG.