Utilizing ultrafast optical pump-probe spectroscopy, we investigate the coexistence and competition of electronic orders in the bilayer nickelate ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$. Our results reveal two coexisting density waves that can be selectively manipulated with light. We directly identify a spin-density wave (SDW) with electronic nematicity emerging below $T_{\mathrm{SDW}}$ $\approx 140$ K by measuring its spin dynamics, and discover a distinct, nonmagnetic charge order appearing below $T_{\mathrm{DW}}$ $\approx 115$ K. The central finding is the demonstration of differential optical control: the charge order is fragile, completely suppressed by a pump fluence of approximately 40 $\mu \mathrm{J}/{\mathrm{cm}}^2$, while the SDW is remarkably robust, persisting to 200 $\mu \mathrm{J}/{\mathrm{cm}}^2$. This work establishes a clear hierarchy in the stability of competing electronic orders and provides a powerful method for disentangling their interplay in quantum materials.

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• Charge density waves
• Charge order
• Electronic structure
• Spin density waves
• High-temperature superconductors
• Ultrafast pump-probe spectroscopy