Oct 9 2014
A quantum probe for measurement of electric field strength has been developed by researchers belonging to the National Institute of Standards and Technology (NIST) and the University of Michigan.
The new technique is based on the quantum properties of atoms, and is linked to the International System of Units (SI).
Commonly used electric field probes possess limited sensitivity and frequency range. They need laboratory calibrations that are often not precise. Further, the field that is being measured also gets disturbed during the process. Also, linking SI units and the measurements that are derived is a complex procedure.
The electric-field probe has a wide range; it can measure field strengths ranging from 1-500GHz and could possibly measure up to 1THz. This range covers sub-terahertz, millimeter-wave, microwave and radio bands. The probe can measure field strengths that are as low as 0.8mV/m.
This method is based on quantum properties that can be predicted and this enables a self-calibration feature that improves the accuracy of measurement. It will also help calibrate other instruments and may enable traceable calibrations in the sub-terahertz and millimeterspectrum bands.
The researchers made atoms reach high-energy Rydberg states using red and blue lasers. Atoms in the Rydberg state are very reactive and sensitive to electromagnetic fields. When an electric field is generated by a source, it affects the light spectrum that is absorbed by the atoms.
The electric field strength is calculated by measuring the vibrations in atoms when they change between energy levels. The researchers used cesium and rubidium atoms for measuring the strength in various parts of the spectrum.
This novel method enables calibrated measurements of above 100GHz frequency, which would be useful for development of sophisticated communications systems. Further, the probe may also be used in applications requiring densely packaged electronics. The new technique could aid in improving the accuracy and sensitivity of tests and in calibrating nano-electronic systems, sensors and antennas.