Hyeonjae Kim

Optically pumped magnetometers exploit the collective spin dynamics of alkali-vapor ensembles to achieve high sensitivity in compact sensor platforms, enabling applications in biomagnetic sensing, magnetic navigation, and magnetic surveys. In this study, we demonstrate an all-optical pulsed rubidium atomic magnetometer for magnetic anomaly mapping of subsurface transportation infrastructure. The optically pumped rubidium atomic magnetometer employs laser mode hopping in a single-beam configuration to perform sequential optical pumping and off-resonant probing for free induction decay readout. During the probing period, the total scalar magnetic field is determined from the Larmor frequency of the rubidium spin precession. The magnetometer was mounted on a drone platform and used for magnetic-field surveys over the Boryeong undersea tunnel at flight altitudes of 50, 100, and 150 m. The residual magnetic anomaly maps showed an elongated anomaly pattern near the mapped tunnel location. Line-profile analysis quantified the altitude dependence of the anomaly amplitude and spatial width. Magnetic anomaly measurements over an underground high-speed railway in Sejong are also presented as a second field demonstration.