A new approach for highly sensitive magnetic field sensors uses sunlight instead of the energy-hungry lasers that previous devices used to make their measurements.
Lasers can use approximately 100 watts of power, which is equivalent to maintaining a bright incandescent bulb. The innovation could free quantum sensors from this energy requirement. In an upcoming issue of Physical Review X Energy, researchers will describe a prototype that is environmentally friendly and technologically advanced
The most innovative aspect of this device is the use of sunlight. It does not convert light into electricity using solar cells. According to Jiangfeng Du, a physicist at the University of Science and Technology of China in Hefei, sunlight replaces the light from the laser.
Quantum magnetometers often contain a powerful green laser to measure magnetic fields. The laser illuminates a diamond with atomic defects (SN: 02/26/08). When nitrogen atoms replace some of the carbon atoms that make up pure diamonds, defects are created. The green laser causes nitrogen defects to fluoresce and emits red light with an intensity that depends on the strength of nearby magnetic fields.
The new quantum sensor also needs the green light. It is rich in sunlight, as evidenced by the green wavelengths reflected off tree leaves and grass. To collect enough sunlight to power their magnetometer, Du and his colleagues replaced the laser with a 15-centimetre-wide lens. Then they removed all colors except green from the light and focused it on a diamond with nitrogen atom defects. As with laser-equipped magnetometers, the result is red fluorescence indicating magnetic field strengths.
Transforming energy from one form to another is inherently inefficient (SN: 7/26/2012). Researchers claim that by avoiding the conversion of sunlight into electricity to power lasers, their method is three times more efficient than lasers powered by solar cells.
According to the researchers, quantum devices that respond to other factors, such as electric fields or pressure, could also benefit from the solar-powered method. In particular, space-based quantum technology could harness the intense sunlight outside of Earth’s atmosphere to provide light optimal for quantum sensors. The remaining light, at wavelengths not used by quantum sensors, could be used to power solar cells that process the quantum signals.
The solar-powered magnetometer is just the beginning of the merging of quantum and green technology.
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