Composition engineering of spray pyrolyzed Mn-doped nickel oxide nanostructures for photonics applications in ultrafast temporal regimes

The development of multifunctional Mn-doped NiO thin films offers versatile platforms for light-based applications. Spray-pyrolyzed Mn-doped NiO films exhibit strong third-order nonlinear optical responses. Under nanosecond laser excitation, the highest third-harmonic generation (THG) efficiency was achieved for the 3 wt% Mn-doped film, attributed to defect states that facilitate photoexcitation and carrier relaxation. Under picosecond excitation, the 1 wt% Mn-doped film yielded the strongest THG response, with the third-order nonlinear susceptibility (χ³) increasing from 8.14 × 10⁻²¹ m²/V² (undoped) to 12.96 × 10⁻²¹ m²/V². This enhancement is linked to ultrafast transient processes and the increased free carrier density introduced by Mn incorporation, which strengthens light–matter interactions. These results highlight Mn-doped NiO thin films as promising candidates for ultrafast photonic applications, paving the way for their integration into advanced nonlinear optical devices.