High contrast Ramsey fringes with coherent-population-trapping pulses in a double lambda atomic system

Area of Science:

• Atomic Physics
• Quantum Optics
• Laser Spectroscopy

Background:

• Coherent population trapping (CPT) is a quantum interference phenomenon used in atomic spectroscopy.
• Classical Ramsey spectroscopy involves sequences of resonant pulses to probe atomic transitions.
• Existing CPT techniques often suffer from limited fringe contrast and broadening effects.

Purpose of the Study:

• To demonstrate Raman-Ramsey fringes using a double lambda scheme in a cesium atomic ensemble.
• To investigate the impact of pulsed optical radiation and specific laser polarization on fringe characteristics.
• To achieve higher contrast and narrower fringe widths compared to conventional methods.

Main Methods:

• Utilized a double lambda excitation scheme with linearly perpendicular polarized laser beams in Cs vapor with N2 buffer gas.
• Employed pulsed optical radiations for preparing atomic state superposition and detecting fringe signals.
• Applied a long trapping pulse for state preparation and a short pulse for fringe detection without dark state perturbation.

Main Results:

• Successfully observed Raman-Ramsey fringes with significantly higher contrast than simple lambda schemes.
• Achieved narrow fringe widths, scaling as 1/(2T), where T is the time interval.
• Demonstrated that the pulsed trapping technique overcomes saturation limitations, improving signal quality.

Conclusions:

• The double lambda scheme combined with pulsed optical radiation provides a robust method for generating high-contrast Raman-Ramsey fringes.
• This technique offers improved precision in probing atomic states, with potential applications in metrology and quantum information.
• The modified Ramsey sequence allows for sensitive detection without disturbing the prepared quantum superposition.