Design of green light sources using nonlinear photonics and on-chip pump lasers

A fully-functional photonic integrated circuit (PIC) platform with supporting active and passive components in the green part of the visible spectral regime is of significant research interest for next-generation optical systems. Here we design highly-integrated ∼3.5 mm long PICs at green wavelengths, which consist of on-chip GaAs-based near-infrared pump lasers, SiN-LiNbO3 hybrid waveguides and ring resonators for nonlinear frequency conversion. The waveguides in the PICs are designed to eliminate etching of LiNbO3, reducing fabrication challenges. Efficient wavelength of 1062 nm pump to 531 nm coherent light is achieved by employing modal phase matching. Unlike a quasi-phase matching technique, modal phase matching enables poling-free operation and further eases device fabrication with comparable performance in terms of second harmonic generation efficiency. The effective nonlinear mode-overlap factor between 1062-nm-TE00 and 531-nm-TE01 modes in the hybrid waveguide is calculated to be 26%. For robust on-chip light coupling between pump laser and waveguide, a calculated maximum coupling efficiency of -2.3 dB is achieved. The theoretical work presented is an initial step towards demonstrating complex non-telecom PICs which could offer a comprehensive range of photonic functionalities.