Efficient visible light generation in a femtosecond PPLN optical parametric oscillator using an uneven poling duty cycle

Summary form only given. Quasi-phase-matching (QPM) techniques for sum frequency generation in optical parametric oscillator periodically poled nonlinear crystals LiNbO/sub 3/ (PPLN) use simultaneous multiple higher-order QPM. However, only odd-order QPM processes have yielded efficient frequency conversion in the standard periodically poled crystals with 50% duty cycle. Here, we demonstrate experimentally that small deviations of the duty cycle from 50% provide considerable conversion efficiencies for even-order QPM processes, too.