Absolute measurement of the effective nonlinearities of KTP and BBO crystals by optical parametric amplification

Absolute magnitudes of the effective nonlinearity, deff, were measured for seven KTP and six BBO crystals. The deff's were derived from the parametric gain of an 800-nm signal wave in the sample crystals when they were pumped by the frequency-doubled, spatially filtered light from an injection-seeded, Q-switched Nd:YAG laser. The KTP crystals, all type II phase matched with propagation in the X–Z plane, had deff values ranging from 1.97 to 3.50 pm/V. Measurements of gain as a function of phase velocity mismatch indicate that two of the KTP crystals clearly contain multiple ferroelectric domains. For five type I phase-matched BBO crystals, deff ranged from 1.76 to 1.83 pm/V, and a single type II phase-matched BBO crystal had a deff of 1.56 pm/V. The uncertainty in our measurements of deff values is ±5% for KTP and ±10% for BBO.