Enhanced narrow-band EUV emission with controllable azimuthal spectral drift in vortex fields.

We demonstrate pronounced narrow-band high-order harmonic emission driven by three-color vortex fields and reveal an intrinsic azimuthal spectral drift of the enhanced EUV spectral band. Unlike conventional multicolor Gaussian fields, the helical phases of the vortex drivers make the enhancement of the EUV spectral band sensitively dependent on the transverse azimuthal angle, leading to a systematic shift of the enhanced spectral band along the azimuthal direction. This behavior represents a unique spatial-spectral feature of multicolor vortex-field-driven harmonic generation. Moreover, phase-singularity shifting confirms the role of the vortex phase, topological-charge tailoring suppresses the drift through effective-delay compensation, and macroscopic propagation supports the buildup of the enhanced narrow-band EUV emission. These results establish three-color vortex fields as a promising platform for spatial-spectral control of enhanced narrow-band EUV emission.