Hideaki OKAYAMA

R&D Group, Oki Electric Industry Co., Ltd., 550-5 Higashiasakawa-cho, Hachioji, Tokyo 193-8550, Japan

(Received December 14, 2007; Accepted July 2, 2008)

Cascaded sum-frequency-generation (SFG) and difference-frequency-generation (DFG) can implement a wavelength conversion between arbitrary combinations of input and output signal wavelengths. By using a tunable wavelength pump light, the output wavelength can be tuned to a desired wavelength. As in many wavelength conversion devices using the nonlinear optical effect, the group velocity difference between light pulses with different wavelength causes a walk-off effect deforming the output pulse shape. Thus the device length should be kept short to avoid the walk-off effect resulting in limited conversion efficiency. In this report, we propose a method for a quasi-phase matched (QPM) device to maintain the pulse shape of the SFG light pulse along the propagation distance. The output DFG light pulse deformation is suppressed and the conversion efficiency can be increased by extending the device length.

Key words: nonlinear optical effect, wavelength conversion, SFG, DFG, group velocity, walk-off, QPM