Abstract

Nonlinear frequency conversion is an attractive technique for extending the spectral range of solid-state coherent sources. Waveguide interactions are useful to increase the efficiency of devices based on low-power pump lasers, e.g. second harmonic generation (SHG) of the output of AlGaAs laser diodes to produce blue light. While the large nonlinear susceptibility and well-developed waveguide technologies available in LiNbO₃ are attractive for device design, LiNbO₃ does not have adequate birefringence for phasematching SHG of blue light. Compensating for phase-velocity mismatch by reversing the sign of the nonlinear susceptibility with a period equal to the coherence length, quasi-phase-matching (QPM), allows phase-matching of any interaction within the transparency range of the crystal using the large d₃₃ nonlinear coefficient. QPM has been investigated in LiNbO₃ waveguides, where the sign changes were due to periodic reversal of the orientation of the ferroelectric domains accomplished by a patterned doping process.^1-3 We have succeeded in generating green and blue light by QPM SHG of the output of infrared lasers in such waveguides.

© 1990 Optical Society of America