High contrast atomic magnetometer based on coherent population trapping

Abstract

We present an experimental and theoretical investigation of the coherent population trapping (CPT) resonance excited on the D1 line of 87 Rb atoms by bichromatic linearly polarized laser light. The experimental results show that a lin‖lin transition scheme is a promising alternative to the conventional circular-circular transition scheme for an atomic magnetometer. Compared with the circular light transition scheme, linear light accounts for high-contrast transmission resonances, which makes this excitation scheme promising for high-sensitivity magnetometers. We also use linear light and circular light to detect changes of a standard magnetic field, separately.

Magnetic Field Measurement Using Peak-Locked Zeeman Coherent Population Trapping Resonance in Rubidium Vapor

“…5(b) shows the CPT spectrum produced by performing demodulation of the photodetector output by a low-noise LIA at the dither frequency. The spectrum shows dispersive (or derivativelike) Zeeman CPT signals with high contrast and SN R [27]. The (0, 0) CPT is not modulated since it is insensitive to magnetic field dither to the first-order.…”

Dark State Magnetometer Based on Enhanced Acousto-Optics Modulator

“…This is mainly due to a very narrow resonance linewidth, which, depending on the experimental condition, can vary from a few Hz to several KHz. To create the dark state and thus observe a CPT signal that is responsive to changes in the B-field, usually two laser beams from two independent lasers are required [10,14,[19][20][21]. Most commonly, one of the lasers, termed a coupling laser (ω c ), is locked to a given Zeeman sub-level, while the other laser, termed probe (ω p ), is scanned around another sub-level.…”

“…Another method for creating a dark state is to have a single laser plus a method for modulation, such as mechanically dithering the mirror of an external cavity diode laser (ECDL), direct modulation of the injection current, or external phase modulation. There are also reports where, instead of modulating the laser, the magnetic field that is applied to the vapor cell to lift the degeneracy in the atomic ensemble is modulated [12,14,24]. However, this approach is less relevant to our work, because we are interested in changes that are induced by a specific strength of the B-field, thus measuring this strength.…”

“…One of the techniques that has been utilized for developing and creating a sensitive magnetometer is the creation of a coherent dark state in a multi-level quantum system and measurement of its response due to the presence of an external magnetic field [10][11][12][13][14].…”

Ultra-narrow parametric magnetic resonances in a miniature vapor cell

“…A nonlinear magneto-optical rotation magnetometer can obtain a subhertz linewidth by utilizing nonlinear magneto-optical effects [13] and wall coatings [10] . A coherent population trapping magnetometer narrows the linewidth with quantum coherence [14] .…”