High-order sideband generation (HSG) in a one-dimensional direct-gap semiconductor offers new opportunities for attosecond spectroscopy and ultrafast band-structure control. However, conventional interpretations often neglect strong-field–induced band renormalization. Here, we demonstrate that (i) pump-strength–dependent sideband frequency shifts—referenced to the excitation frequency—provide direct evidence of Floquet band dressing, and (ii) sideband-yield modulation furnishes an instantaneous measure of the Floquet band-gap shift with few-meV resolution. We develop a framework to extract both the renormalized band edge and the avoided-crossing gap ${\tilde{\mathrm{\Delta }}}_2$, and we clarify the symmetry-imposed selection rules for odd and even sidebands, arising from simultaneous parity and energy conservation under bichromatic driving. These results establish terahertz-driven HSG as a phase-sensitive, high-resolution probe of light-engineered band structure in quantum materials.

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• Nonlinear optics
• Strong-field-induced spectra
• Floquet systems
• Bloch-Floquet theorem
• High-order harmonic spectroscopy