Non-resonant Bragg scattering four-wave mixing at near-visible wavelengths in low-confinement silicon nitride waveguides

Quantum state coherent frequency conversion processes- such as Bragg -scattering four -wave mixing (BSFWM)-hold promise as a flexible technique for networking heterogeneous and distant quantum systems. In this Letter, we demonstrate BSFWM within an extended (1.2-m) low -confinement silicon nitride waveguide and show that this system has the potential for near -unity frequency conversion in visible and near -visible wavelength ranges. Using sensitive classical heterodyne laser spectroscopy at low optical powers, we characterize the Kerr coefficient ( similar to 1.55 W -1 m -1 ) and linear propagation loss ( similar to 0.0175 dB/cm) of this non -resonant waveguide system, revealing a record -high nonlinear figure of merit (NFM = gamma/ alpha approximate to 3.85 W -1 ) for BSFWM of near -visible light in non -resonant silicon nitride waveguides. We predict how, at high yet achievable on -chip optical powers, this NFM would yield a comparatively large frequency conversion efficiency, opening the door to near -unity flexible frequency conversion without cavity enhancement and resulting bandwidth constraints. (c) 2024 Optica Publishing Group