Quantum erasing of laser emission in N2

Area of Science:

• Atomic and Molecular Physics
• Quantum Optics
• Ultrafast Laser Science

Background:

• Cavity-free lasing in nitrogen ions (N2+) is typically induced by femtosecond laser pulses.
• Lasing without population inversion (LWoPI) phenomena are of significant interest in quantum optics.
• Understanding population dynamics in excited molecular states is crucial for controlling light-matter interactions.

Purpose of the Study:

• To investigate the effect of a delayed twin control pulse on femtosecond laser-induced N2+ lasing.
• To elucidate the underlying mechanisms of lasing suppression within the V-scheme framework.
• To explain the origin of short lasing bursts observed at specific time delays.

Main Methods:

• Experimental setup involving femtosecond laser pulses at 800 nm to induce N2+ lasing.
• Utilizing a delayed twin control pulse to probe population dynamics.
• Theoretical analysis based on the V-scheme model for lasing without population inversion.

Main Results:

• Cavity-free lasing of N2+ is nearly completely suppressed by the delayed control pulse.
• A rapid population transfer between the X2Σg+ and A2Πu states of N2+ is induced by the second pulse.
• This population transfer terminates the conditions necessary for amplification, effectively suppressing lasing.
• Short lasing bursts are observed at delays corresponding to the revival of rotational wave packets.

Conclusions:

• The V-scheme provides a valid framework for understanding the observed suppression of N2+ lasing.
• The delayed control pulse acts by rapidly altering the population distribution, preventing gain.
• The revivals of rotational wave packets correlate with transient conditions that allow for short lasing bursts.