Carrier-Envelope Phase Control of Molecular-Ion Lasing

Carrier-envelope phase (CEP) provides a direct handle on strong-field–prepared coherence in molecular ions, allowing sub-cycle control of ultraviolet stimulated emission with CEP-stabilized, near-single-cycle drivers. We show that self-seeded emission in nitrogen and carbon dioxide ions can be modulated by adjusting the CEP, producing pronounced spectral fine shape changes and phase-sensitive intensity oscillations. The CEP dependence originates from coherent interference between the energy-level coherence and the seed from self-phase modulation by the driven field. The phase difference at different wavelengths can be used for single-shot CEP tagging. Our results link ultrafast waveform control to macroscopic lasing dynamics, and point to molecular-ion air lasing as a practical tool for phase-resolved ultrafast spectroscopy.