N${}_2^{+}$ Lasing: Gain and Absorption in the Presence of Rotational Coherence

Abstract

We simulate the pump-probe experiments of lasing in molecular nitrogen ions with particular interest on the effects of rotational wave-packet dynamics. Our computations demonstrate that the coherent preparation of rotational wave packets in N${}_2^{+}$ by an intense short non-resonant pulse results in a modulation of the subsequent emission from $B^2{\Sigma }_u^{+}\to X^2{\Sigma }_g^{+}$ transitions induced by a resonant seed pulse. We model the dynamics of such pumping and emission using density matrix theory to describe the N${}_2^{+}$ dynamics and the Maxwell wave equation to model the seed pulse propagation. We show that the gain and absorption of a delayed seed pulse is dependent on the pump-seed delay, that is, the rotational coherences excited by the pump pulse can modulate the gain and absorption of the delayed seed pulse. Further, we demonstrate that the coherent rotational dynamics of the nitrogen ions can cause lasing without electronic inversion.

References in corpus (7)

• High-brightness switchable multi-wavelength remote laser in air
• Population Redistribution among Multiple Electronic States of Molecular Nitrogen Ions in Strong Laser Fields
• Self-seeded lasing in ionized air pumped by 800 nm femtosecond laser pulses
• Rotational Quantum Beat Lasing Without Inversion
• Real-time observation of dynamics in rotational molecular wave packets by use of "air laser" spectroscopy
• Transient gain from $N_2^{+}$ in light filaments
• Optical quantum memory for ultrafast photons using molecular alignment

Cited by in corpus (4)

• Electronic State Population Dynamics upon Ultrafast Strong Field Ionization and Fragmentation of Molecular Nitrogen
• Strong Field Ionization of Water: Nuclear Dynamics Revealed by Varying the Pulse Duration
• Strong Field Ionization of Water II: Electronic and Nuclear Dynamics En Route to Double Ionization
• Ramsey interferometry through coherent $X^2{\Sigma }_g^{+}-A^2{\Pi }_u-B^2{\Sigma }_u^{+}$ coupling and population transfer in N${}_2^{+}$ air laser