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

• Nicholas Jaber, Scott Madaras, Andrew Starbuck, Andrew Pomerene, Christina Dallo, Douglas Trotter, Michael Gehl, and Nils Otterstrom
• received 01/25/2024; accepted 04/10/2024; posted 04/11/2024; Doc. ID 519793
• Abstract: 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 quantum coherent frequency conversion in visible and near-visible wavelength ranges. Using sensitive heterodyne laser spectroscopy at low optical powers, we characterize the Kerr coefficient (∼1.55 W^{−1}m^{−1}) and linear propagation loss (∼0.0175 dB/cm) of this non-resonant waveguide system, revealing a record-high nonlinear figure of merit (NFM = γ/α ≈ 3.85 W^{−1}) for BSFWM of near visible light in non-resonant silicon nitride waveguides. We demonstrate 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.