Abstract : Alkali metal (M Li, Na, K)-doped silicon carbide nanosheets (M@SiCNs) have been theoretically investigated to evaluate their geometries, stabilities and nonlinear optical responses through density functional theory. Computationally determined interaction energies confirm the stability of newly designed M@SiCNs materials. The nature of the interactions between alkali metals and SiCNs is explored by non-covalent interaction (NCI) analysis. The doping of alkali metals on silicon carbide nanosheet has led to a maximum of 62% reduction in the E(H–L) gap. The isomer K@SiCNs-III has a maximum hyperpolarizability (βo) of 7.7×104 au in comparison with that of undoped SiCNs. The frequency-dependent SHG and EOPE are also determined. The value of 4.47×108 au is observed for ESHG, while for induced dc-Kerr effect the value is 3.96×109 au. Furthermore, these structures have a high nonlinear quadratic refractive index of 1.32×10–14 au. The significant NPA charges, low ionization potential values, higher chemical softness values, low excitation energies and DOS spectra justify the heightened NLO response. The TD-DFT study shows that these complexes have λmax in the visible and near-IR regions. This work may provide valuable guidelines for designing new silicon carbide-based materials with enhanced NLO response.