A magneto-encephalography device including a plurality of laser threshold magnetometers for measuring a magnetic field is provided. Each laser threshold magnetometer includes an optical cavity, a laser medium which together with the optical cavity has a laser threshold； a laser pump； and a radio-frequency (RF) drive applied to the laser medium at or around a particular resonance frequency which varies depending on the magnetic field, such that depending on the value of the physical parameter, the RF drive induces transitions between at least two states of the laser medium, each state causing a different laser threshold in an intensity of a laser output, wherein the intensity of the laser output provides a measurement of the magnitude of the magnetic field； wherein the laser threshold magnetometers are configured to be placed on a head of a subject to be monitored.
