Steep atomic dispersion induced by velocity-selective optical pumping

Area of Science:

• Atomic, Molecular, and Optical Physics
• Quantum Optics
• Laser Physics

Background:

• Controlling the speed of light is crucial for applications in quantum information and optical communications.
• Dispersion, the phenomenon where the speed of light depends on its frequency, plays a key role in light propagation.
• Alkali vapors offer unique properties for manipulating light due to their atomic structure.

Purpose of the Study:

• To demonstrate a novel method for preparing broadband sign-reversible dispersion in alkali vapor.
• To investigate the potential for controlling the group velocity of light using this method.
• To explore the practical implications for light-speed manipulation in atomic systems.

Main Methods:

• Utilizing velocity-selective optical pumping to induce specific atomic population distributions.
• Employing a heterodyne detection method to precisely measure the refractive index in Rubidium (Rb) vapor.
• Analyzing the spectral characteristics of the dispersion over a 40 MHz region.

Main Results:

• Successfully prepared broadband sign-reversible dispersion in Rb vapor.
• Observed that both normal and anomalous dispersion magnitudes remained nearly constant over a 40 MHz spectral range.
• Achieved significantly reduced (V(g) ≈ c/230) and negative (V(g) ≈ -c/27) group velocities of light.

Conclusions:

• The demonstrated method provides a robust way to achieve sign-reversible dispersion in alkali vapors.
• The ability to control light's group velocity, including negative values, opens new avenues for optical technologies.
• This research contributes to the fundamental understanding and practical application of light-matter interactions.