Efficient Broadband Frequency Conversion Using Engineered Apodized ${\mbi \chi}^{({\bf 2})}$ Gratings and Fundamental Harmonic Resonance

Apodized step-chirped grating in quasi-phase matched lithium niobate waveguide with fundamental-harmonic resonance are proposed and designed for efficient broadband frequency converters. The optimized values of back-facet reflectivity and input power are calculated to achieve maximum efficiency.