Quantum and noninear optics of a cold-atom ring laser with controlled dispersion

When a pulse of light propagates through a medium it becomes distorted, and may appear to slow down, speed up, or even reverse direction. Although the principle of causality is not violated, these effects have ramifications for lasers whose gain media have exotic refractive properties. Such lasers have been proposed for frontier applications in timekeeping, electromagnetic and gravitational field sensing, and inertial navigation. Despite the potentially disruptive nature of these technologies, experimental demonstrations are still few and debate surrounds some aspects of the theory.

We are building a ring laser using a gas of cold atoms as a gain medium, tuning the group index through controlled quantum coherences. In the regime of slow light propagation, such a laser shows reduced sensitivity to environmental perturbations, making it attractive for active time/frequency standards. In the so-called superluminal regime, the lasing wavelength is hypersensitive to rotations via the Sagnac effect, making it promising for next generation gyro navigation systems. However the noise properties of such lasers are not well understood and only preliminary measurements have been made. We will help fill gaps in our understanding of lasing in fast and slow light media, and lay the foundation for future technologies based on their application.