Carrier-wave Rabi-flopping signatures in high-order harmonic generation for alkali atoms

Area of Science:

• Atomic Physics
• Quantum Optics
• Nonlinear Optics

Background:

• Rabi flopping describes the coherent oscillation of a two-level quantum system under a resonant driving field.
• High-order harmonic generation (HHG) is a nonlinear process where atoms emit high-energy photons when interacting with intense laser fields.
• The area theorem traditionally describes the behavior of the population inversion in a two-level system under pulsed excitation.

Purpose of the Study:

• To theoretically investigate carrier-wave Rabi flopping in alkali atoms (sodium and potassium).
• To analyze the features of third-harmonic generation in Na and K atoms under different pulse areas.
• To correlate observed phenomena with Rabi flopping and the area theorem.

Main Methods:

• Numerical simulations of high-order harmonic generation (HHG).
• Theoretical investigation of carrier-wave Rabi flopping.
• Analysis of ground state population dynamics.
• Focus on third-harmonic generation in sodium (Na) and potassium (K) atoms.

Main Results:

• A unique peak in the third harmonic of Na atoms for a 2π pulse area was correlated with conventional Rabi flopping.
• For larger pulse areas, carrier-wave Rabi flopping was observed, exhibiting a more complex structure in the third harmonic.
• These characteristics in K atoms demonstrated the breakdown of the area theorem.

Conclusions:

• Carrier-wave Rabi flopping can be observed in alkali atoms via HHG.
• The breakdown of the area theorem is confirmed in atomic systems under specific conditions.
• HHG provides a sensitive probe for studying quantum coherent phenomena like Rabi flopping.