Abstract: Broadband nonlinear frequency conversions of optical waves are widely employed in multiple areas of optics and photonics. However, the broadening of conversion bandwidth is often at a cost of reduction in efficiency, which may induce a limitation on practical applications. Here we theoretically propose a novel design of LiNbO₃ ridge waveguides on LiTaO₃ substrates which can be used for efficient and broadband second harmonic generation. Through group velocity engineering of the ridge waveguides, acceptance bandwidth over 20 nm with a high conversion efficiency of >25%W ^-1cm ^-2 is achieved at telecom-band.

Key words: second harmonic generation, lithium niobate ridge waveguide, dispersion manipulation