Multi-timescale frequency-phase matching for high-yield nonlinear photonics.

Integrated nonlinear photonics struggles to deliver wafer-scale functional device yields: Nanometer-level fabrication variations compromise the strict frequency-phase matching mandated by energy- and momentum-conserving nonlinear processes. We introduce nested frequency-phase matching, a passive scheme that relaxes these constraints, and implement it in a two-timescale lattice of commercially available silicon nitride (SiN) coupled ring resonators for harmonic generation. The nested lattice simultaneously generates ultrabroad bandwidth light in the fundamental-, second-, third-, and fourth-harmonic bands and achieves 100% multifunctional wafer-scale device yield, all passively and without geometry fine-tuning. Distinct spatial and spectral signatures confirm the predicted relaxation of frequency-phase matching, establishing a scalable route for chip-scale nonlinear optics. Our approach provides possibilities for integrated frequency conversion and synchronization, self-referencing, precision metrology, squeezed-light sources, and nonlinear optical computing. Editor's summary: Integrated nonlinear photonic technologies struggle in terms of scalability. The strict requirements of frequency and phase matching can be corrupted by the tiniest fabrication defects, leading to rapid performance deterioration nonuniformity across a wafer. Mehrabad et al. demonstrate a platform based on coupled silicon nitride ring resonator arrays that relax the strict phase-matching conditions and allow for broadband operation, thus easing the requirement for device fabrication. Being robust against fabrication errors, the approach should allow the development of integrated nonlinear photonic technologies at scale. —Ian S. Osborne [ABSTRACT FROM AUTHOR]