NONLINEAR-OPTICAL PROPERTIES OF PPLN (PERIODICALLY POLED LINBO3)

Quasi-phase matched (QPM) second harmonic generation (SHG) in a LiNbO3 :Mg:Nd crystal was studied with a pulsed dye laser. The ferroelectric domain-inverted periodic structure (period of about 4.8 mu m) was form ed by modulating the Nd-concentration during the crystal growth proces s. In a collinear geometry where the fundamental wavevector is perpend icular to the domain walls, phase-match between the fundamental and se cond harmonic was obtained by tuning the fundamental wavelength. The c orresponding SHG efficiency shows a sharp peak at the phase-matching w avelength of 956 nm, and asymmetric sidebands. The effect of irregular domain sire was numerically calculated to explain the asymmetry in th e experimental data. In this collinear configuration the largest nonli near optical coefficient d(33) was dominantly used giving an energy co nversion efficiency of 23.3% with a fundamental beam intensity of 160 MW/cm(2).