Ultrafast optical control of magnetization is well established in ferromagnets, yet its realization in nonmagnetic semiconductors, where spin degeneracy typically precludes net magnetization, remains a significant challenge. Here, using real-time, time-dependent density functional theory (RT-TDDFT), we investigate the ultrafast spin dynamics in monolayer InSe, where spin-orbit coupling and crystal symmetry enable light-induced magnetization through spin-flip torque. Under an in-plane circularly polarized pulse, spin-flip transitions dominate at low intensities, generating a substantial out-of-plane magnetization. With increasing field strength, saturation-like behavior emerges in the spin-flip channels, suppressing this pathway and making competing excitation channels more accessible, leading to suppression or even reversal of the net magnetization. Furthermore, we show that strong linearly polarized pulses break time-reversal symmetry via carrier population imbalance, producing a residual magnetization. These results reveal a nonperturbative regime of light-matter interaction, where magnetization is induced purely by ultrafast carrier dynamics without invoking lattice or thermal effects, and offer new pathways for all-optical spin control in nonmagnetic quantum materials.

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• Magnetization dynamics
• Photoinduced effect
• Spin-orbit coupling
• Ultrafast magnetic effects
• Time-dependent DFT