We investigate theoretically the coherent dynamics of helium photoionization driven by a pair of time-delayed laser pulses using the $(1+1)$-dimensional two-electron time-dependent Schrödinger equation. Our numerical calculations reveal that the resulting photoelectron spectra exhibit Grobe–Eberly doublets accompanied by Ramsey-like interference fringes. Notably, the contrast of these fringes varies periodically with both laser intensity and interpulse time delay. By evaluating the purity of the reduced density matrix, we attribute this modulation to variations in the bipartite entanglement between the emitted photoelectron and the residual dressed ion. The mechanism controlling the entanglement lies in the interplay between ionic population and coherence, governed by the quantum phase set by the pulse area and the optical phase introduced by the interpulse delay. Moreover, tuning the laser parameters can induce out-of-phase shifts between ion-channel-resolved spectra, providing experimental access to probe entanglement during the buildup of Rabi dynamics via coincidence measurements.

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• Coherent control
• Electron correlation calculations for atoms & ions
• Light-matter interaction
• Single- and few-photon ionization & excitation