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

当光脉冲通过介质传播时，它会失真，并可能表现为减速、加速，甚至反向。尽管没有违反因果关系原则，但这些效应对其增益介质具有奇异折射特性的激光器有影响。这类激光器已被提议用于计时、电磁和引力场传感以及惯性导航等前沿应用。尽管这些技术具有潜在的颠覆性，但实验演示仍然很少，围绕该理论的某些方面也存在争议。我们正在建造一种环形激光器，使用冷原子气体作为增益介质，通过受控的量子相干来调谐群指数。在慢光传播的情况下，这种激光器对环境扰动的敏感性降低，这使得它对主动时间/频率标准很有吸引力。在所谓的超光速区域，激光波长通过Sagnac效应对自转非常敏感，这使得它在下一代陀螺导航系统中很有希望。然而，这种激光器的噪声特性还不是很清楚，只进行了初步的测量。我们将帮助填补我们对快光和慢光介质中激光的理解空白，并为基于其应用的未来技术奠定基础。

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.