Coherent Broadband Spectrum Generation in Rectangular Silicon Core Buried Waveguide Operated at Telecommunication Wavelength

This research endeavors to generate a coherent and flat supercontinuum by designing and optimizing silicon core rectangular buried waveguides, featuring various width and height configurations of the core operating at the wavelength of 1550 nm. By estimating the effective index of the system, we compute the group velocity dispersion (GVD) parameters and higher-order dispersive terms, while concurrently determining the nonlinear Kerr coefficient crucial for pulse propagation. The propagation of chirp-free high-power Gaussian pulse is investigated through the proposed waveguide by numerically solving the generalized nonlinear Schrödinger equation. Our investigation reveals the attainment of a sufficiently broadened and notably flat supercontinuum for waveguides exhibiting a slightly positive GVD parameter. Leveraging the high nonlinearity of silicon-based waveguides relative to non-semiconductor counterparts, we achieve broad spectral coverage (~ 600 nm) over significantly shorter propagation lengths (~ mm), maintaining the favorable flatness and coherence parameters which can be extended even for a few mm length. To the best of our knowledge, such a rectangular/square Si core buried SOI waveguide has yet to be reported for the coherent supercontinuum generation in the telecommunication band.