Breaking the energy-symmetry-based propagation growth blockade in magneto-optical rotation
Chengjie Zhu, Feng Zhou, Eric Y. Zhu, Edward W. Hagley, Lu Deng
The magneto-optical polarization rotation effect has prolific applications in various research areas spanning the scientific spectrum including space and interstellar research, nano- technology and material science, biomedical imaging, and sub-atomic particle research. In nonlinear magneto-optical rotation (NMOR), the intensity of a linearly-polarized probe field affects the rotation of its own polarization plane while propagating in a magnetized medium. However, typical signals of conventional $\Lambda-$scheme atomic magnetometers based on NMOR effect are peculiarly small, necessitating the employment of sophisticated equipment under complex operational conditions. Here, we show the presence of an energy-symmetry blockade that undermines the NMOR in the conventional $\Lambda-$scheme atomic magnetometers. We further demonstrate, both experimentally and theoretically, an inelastic wave-mixing technique that breaks this NMOR blockade, resulting in more than two orders of magnitude NMOR optical signal- to-noise ratio (SNR) enhancement never seen in the conventional single-beam $\Lambda-$scheme atomic magnetometers. This new technique, demonstrated with substantially reduced light intensities, may lead to many applications especially in the field of chip-level photonics- based bio-magnetic research and high-resolution passive magnetic imaging.