Intracavity second-harmonic generation of 1.06 mu m in GdCa4O(BO3)(3) crystals

The characteristics of intracavity second-harmoni generation (SHG) at 1.06 mum in GdCa4O(BO3)(3) (GdCOB) crystals cut for different type I phase-match ing (PM) directions of (theta, phi) = (66.8 degrees, 132.3 degrees); (19.4 degrees, 0 degrees); (90 degrees, 36 degrees) have been investigated. It wa s found that the intracavity SHG was significantly efficient in the PM dire ction of (66.8 degrees, 132.3 degrees), and that the intrinsic lower effect ive nonlinear coefficient (d(eff)) was responsible for the less-efficient S HG in the other two directions. A maximum CW SHG output power of 2.81 W was obtained with an optical conversion efficiency of 18.7%, while the corresp onding effective intracavity SHG efficiency was determined to be 41.3%. The intracavity SHG efficiency of GdCOB has been found to reach two-thirds of that obtained with type II phase-matching KTiOPO4 (KTP).