Enriching Si quantum dots in a Si-rich SiNxmatrix for strong χ(3)optical nonlinearity

To meet the demand of all-optical data processing applications, the SiNx layer with enriching Si quantum dots (Si-QDs) for achieving strong optical nonlinearity is demonstrated with its χ(3) coefficient enhanced by three orders of magnitude larger than that of stoichiometric Si3N4. With excessive Si concentration enriched from 16.3% to 23.4%, the dense Si-QDs apparently self-assemble in the SiNx matrix with an average size of ∼0.95 nm and volume density of 5 × 1019 # cm−3. The Si-QD doped Si-rich SiNx not only enlarges its third-order nonlinear absorption coefficient from 0.01 to 1.8 m GW−1, but also increases its nonlinear refractive index from 5.7 × 10−13 to 9.2 × 10−12 cm2 W−1 at a wavelength of 800 nm, as attributed to the localized excitons with decreased effective Bohr radius in quantum confined Si-QDs. Such a SiNx:Si-QD material enables strong optical nonlinearity in compact nonlinear nanophotonic waveguide devices developed for future all-optical data processors.