An atomic magnetometer that simultaneously achieves high sensitivity, simple fabrication and small size. This design is based on a diverging (or converging) beam of light that passes through an alkali atom vapor cell and that contains a distribution of beam propagation vectors. The existence of more than one propagation direction permits longitudinal optical pumping of atomic system and simultaneous detection of the transverse atomic polarization. The design could be implemented with a micro machined alkali vapor cell and light from a single semiconductor laser. A small modification to the cell contents and excitation geometry allows for use as a gyroscope.
Gyroscopes sense rotation. In combination with magnetometers, gyroscopes are used many applications, including inertial navigation and platform stabilization. The NIST invention enables multitasking measurement capabilities and is the first to demonstrate simultaneous measurement of rotation, rotation angle and acceleration with a single source of atoms.
As of the date of the patent, a variety of vapor cell magnetometers and gyroscopes existed. They were expensive, and for some uses the signal strength and data acquisition speed needed to be increased to enable increased sensitivity measurements. In addition, a smaller design was needed for use in compact systems that could be used in the field.
The NIST invention solves these issues. A single diverging laser beam allows the measurement of both longitudinal and transverse spin polarizations of atoms within the cell. The design can be implemented with a micromachined alkali vapor cell and light from a single semiconductor laser. Differential measurements made with the quadrant photodetector suppress noise. A small modification to the cell contents and excitation geometry allows for use as a gyroscope. Atomic magnetometers are scalar sensors, which means they sense the magnitude of the magnetic field, rather than the projection along one spatial direction. This is particularly important for applications on moving platforms since platform motion adds considerable noise to a vector sensor as the angle between the field and the sensor axis changes.
The compact atomic magnetometer and gyroscope is likely to be of significant interest to the Department of Defense and the numerous manufacturers that provide equipment to DOD. It will also be appealing to makers of inertial navigation systems for aircraft and other transportation modes as well as the expanding market for autonomous vehicles.