We demonstrate that quantum-trajectory interference in high-order harmonic generation can be efficiently modified by tailoring the symmetry of orthogonally polarized two-color laser fields via the temporal delay. Numerical simulations based on the three-dimensional time-dependent Schrödinger equation reveal that an appropriate delay enables selective enhancement of short trajectories while suppressing long trajectories. By combining time-frequency analysis with classical analysis, we show that this trajectory selection originates from the symmetry of the driving field, which governs the relative timing of electron ionization and recollision. The resulting trajectory modulation exhibits a robust periodic behavior that is independent of the laser intensity ratio and the atomic species, but strongly dependent on the frequency ratio of the two-color field. An empirical relation is established to characterize the periodicity of the trajectory selection. The demonstrated trajectory-selection mechanism may provide useful insight for future studies of attosecond pulse generation in orthogonally polarized two-color laser fields.

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• Atomic & molecular processes in external fields
• Coherent control
• Strong-field-induced spectra