The authors report efficient third harmonic generation of microjoule picosecond pulses at 355 nm in the nonlinear optical material BiB3O6. Using two crystals of BiB3O6 cut for type I (e+e→o) phase matching in optical yz plane for second and third harmonic generation and fundamental pulses from a mode-locked, amplified picosecond Nd:YAG laser at 1.064 micron, they have achieved conversion efficiencies of as much as 50% at 355 nm. Third harmonic pulse energies of up to 216 microjoule in 29 ps pulses at 25 Hz repetition rate have been obtained for 35 ps fundamental pulses. They have also determined the magnitude of two-photon absorption coefficient in BiB3O6 at 355 nm to be 0.71 and 1.37 cm/GW for ordinary and extraordinary polarizations, respectively.
