We have achieved efficient simultaneous intracavity doubling of the signal frequency and sum-frequency generation between the signal and the pump in a periodically poled LiNbO<sub>3</sub> femtosecond optical parametric oscillator pumped by a Ti:sapphire laser. The responsible mechanisms are second-, third-, and fourth-order quasi-phase matching (QPM). An ~56% poling duty cycle permits efficient even-order QPM. Femtosecond pulses tunable in the visible were generated with a total efficiency of more than 8% for only 480-mW pump power at 80 MHz. Optimization of the poling duty cycle can improve the efficiency further.
© 2001 Optical Society of America
(140.7300) Lasers and laser optics : Visible lasers
(190.2620) Nonlinear optics : Harmonic generation and mixing
(190.4410) Nonlinear optics : Nonlinear optics, parametric processes
(190.4970) Nonlinear optics : Parametric oscillators and amplifiers
(190.7110) Nonlinear optics : Ultrafast nonlinear optics
X. P. Zhang, J. Hebling, J. Kuhl, W. W. Rühle, and H. Giessen, "Efficient intracavity generation of visible pulses in a femtosecond near-infrared optical parametric oscillator," Opt. Lett. 26, 2005-2007 (2001)