Optimal Phase Matching of Three Wave Mixing in BBO and KTP Crystals

Abstract

The newly developed crystals of Beta-Barium-Borate(BBO) and KTP have been identified as the excellent candidates for the generation of coherent sources in UV (using BBO) and visible (using KTP), and mid-IR(2-4 um) (using KTP and BBO). BBO crystal with an effective nonlinear coefficient(deff) about 4-7 times that of KDP promises various applications through its features of high damage threshold(5-10 GW/cm), wide transparency(0.19-3 um) wide temperature acceptance(55 degrees) and chemically and mechanically stable. KTP crystal on the other hand has a cut-off doubling phase-matching at about 1 micron. This crystal, however, is still attractive due to its high deff(12-17 times that of KDP) and the extremely wide temperature, angular and spectral acceptance widths. Comparison with second harmonic generation(SHG), much less work has been done in frequency-mixing using BBO and KTP crystals. The three-wave-mixing(TWM) processes to be discussed in this paper shall include sum-frequency-mixing (SFM), difference-frequency-mixing(DFM) and optical parametric oscillation(OPO). The optical deff for various polarization configurations will be calculated for both type I and type II BBO and KTP. The key issues for the performance of TWM in these crystals will be analyzed. Finally, applications for the generation of tunable coherent sources will be presented.