Difference frequency generation in optically poled silicon nitride waveguides

Abstract

Difference-frequency generation (DFG) is elemental for nonlinear parametric processes such as optical parametric oscillation and is instrumental for generating coherent light at long wavelengths, especially in the middle infrared. Second-order nonlinear frequency conversion processes like DFG require a second-order susceptibility 𝜒 (2) , which is absent in centrosymmetric materials, e.g. silicon-based platforms. All-optical poling is a versatile method for inducing an effective 𝜒 (2) in centrosymmetric materials through periodic self-organization of charges. Such all-optically inscribed grating can compensate for the absence of the inherent second-order nonlinearity in integrated photonics platforms. Relying on this induced effective 𝜒 (2) in stoichiometric silicon nitride (Si 3 N 4 ) waveguides, second-order nonlinear frequency conversion processes, such as second-harmonic generation, were previously demonstrated. However up to now, DFG remained out of reach. Here, we report both near-and non-degenerate DFG in all-optically poled Si 3 N 4 waveguides. Exploiting dispersion engineering, particularly rethinking how dispersion can be leveraged to satisfy multiple processes simultaneously, we unlock nonlinear frequency conversion near 2 μm relying on all-optical Ezgi Sahin and Boris Zabelich contributed equally to this work.

Coherent Photogalvanic Effect for Second-Order Nonlinear Photonics

“…There has been interest on the decay dynamics of the QPM gratings in fibers as it helps our understanding of the trap locations, time constants and physical mechanism of the process. The charge gratings decay faster at higher temperatures [22] or when exposed to high-energy photons [22,31,53]. From Eq.…”

“…It is exploited for several linear [25] and nonlinear applications, such as four-wave mixing [26,27], third-harmonic generation (THG) [28], supercontinuum [29] and Kerr comb [30] generation using χ (3) nonlinearity. AOP now allows to add χ (2) processes, such as SHG, differencefrequency generation [31] and spontaneous parametric down-conversion [32], to the already impressive nonlinear toolbox of Si 3 N 4 . Recently, there have been several qualitative attempts to explain the time dynamics of AOP, which exhibits growth and saturation, and its dependence on waveguide dimensions [21,22,33].…”