RUI: Coherence-Derived Light Fluctuations for Atomic Magnetometry

Lewis And Clark College, Portland OR

Investigators

Abstract

Significant advancements in 21st century physics have relied on the discovery that properties of atoms are not fixed, but can be changed by interactions with laser light. The ability to understand and control these sensitive interactions is also the key to the creation of new atom-light based technologies. Some atom-light interactions are sensitive to the surrounding magnetic field. As an example, an atom is extremely selective about the precise colors of light it absorbs, but when it is placed in a magnetic field, the atom's color choices will shift depending on the strength of the field. Such interactions can be used as the foundation of a device, called an "atomic magnetometer," that can measure unknown magnetic fields. This investigation studies interactions between laser light and a specially prepared gas of atoms that is sensitive to small variations in the surrounding magnetic field. The special preparation uses two lasers and a controlled magnetic field to temporarily but dramatically change how laser light travels through a gas of atoms. As a result, the laser light's brightness fluctuates, or flickers, in ways that are not yet fully understood. These fluctuations not only carry information about the atoms, but they are also especially sensitive to magnetic field variations. This research will further our scientific understanding of atom-light interactions, which is of broad interest for many technological applications. Simultaneously, the research will produce new techniques for detecting small, unknown magnetic fields, like the magnetic fields emitted from the human heart. The new detection methods will potentially impact a broad range of medical and scientific fields, and because they make use of low-cost and potentially portable laser systems, any resulting technological applications will be widely accessible and suitable for use outside of the laboratory environment. Undergraduate students will be involved at all stages of this research agenda, preparing them for careers in research science and other STEM-related fields. Light intensity fluctuations derived from atomic coherence can encode valuable information about coherence dynamics in an atomic vapor. Furthermore, they provide a platform for a new class of compact and simple atomic magnetometers. This research agenda uses low-cost, free-running diode lasers with inherent frequency noise that is converted into information-rich intensity noise near an atomic resonance. The amplitude and phase of the intensity fluctuations are particularly sensitive to small magnetic field variations near an atomic coherence between Zeeman sublevels. Hanle effect Electromagnetically Induced Transparency will be induced in rubidium vapor and used to prototype and optimize a novel magnetometry technique relying on coherence-derived light fluctuations. The converted laser intensity noise will be studied using self-correlations and spectrum analysis. The findings will deepen our understanding of the relationship between the light fluctuations and the underlying atomic coherence, as well as give us the tools to build a new atomic magnetometer. Moreover, the results will provide useful insight for mitigating noise from imperfect lasers.