Abstract

Tailoring the spatial and angular-momentum structure of high-harmonic radiation is an important route toward controllable extreme-ultraviolet structured light. Here, we introduce an orbital angular momentum (OAM)-resolved photon-channel framework to elucidate spatial-mode formation in high-harmonic generation driven by bichromatic vortex fields. Combined with numerical solutions of the time-dependent Schrödinger equation for argon, this framework shows that the spatial structure of the emitted harmonics is governed by spectral broadening and interference among dominant OAM-carrying photon channels. This mechanism drives a continuous transition from clean vortex beams at harmonic peaks, characterized by high OAM purity, nearly pure circular polarization, and strong transverse coherence, to disordered speckle-like patterns in harmonic valleys, where multi-channel interference induces pronounced phase distortion. These results identify photon-channel interference as a useful mechanism for controlling the OAM, polarization, and spatial coherence of harmonic beams. The proposed analysis provides a field-control and OAM-channel framework that may be extended in future studies to structured-light probes of ultrafast dynamics and topological phases in quantum materials.

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