Abstract: The present invention uses nonlinear crystal waveguides to provide a continuous wave and picoseconds pulse laser systems that gives an order-of-magnitude increase in IR-to-visible conversion efficiency and also provide an order-of-magnitude increase of wavelength range for SHG conversion. The idea of enabling such broad tunability is based on the utilization of a significant difference in the effective refractive indices of the high order and low order modes in the waveguide. This feature enables the difference between the effective refractive indices of the fundamental and second-harmonic waves to be shifted to match the period of poling in a very broad wavelength range.