Light from an optical fiber illuminates the metasurface and is scattered in four
different directions. The intensities are measured by four detectors. From this
measurement the state of polarization of light is detected.
(Photo courtesy of the Capasso Lab/Harvard SEAS)
(January 10, 2016) Ultra-compact polarimeter could improve telecommunications, medical diagnostics and drug testing.
What do astrophysics, telecommunications and pharmacology have in common? Each of these fields relies on polarimeters — instruments that detect the direction of the oscillation of electromagnetic waves, otherwise known as the polarization of light.
Even though the human eye isn’t particularly sensitive to polarization, it is a fundamental property of light. When light is reflected or scattered off an object, its polarization changes and measuring that change reveals a lot of information. Astrophysicists, for example, use polarization measurements to analyze the surface of distant planets, or to map the giant magnetic fields spanning our galaxy. Drug manufacturers use the polarization of scattered light to determine the chirality and concentration of drug molecules. In telecommunications, polarization is used to carry information through the vast network of fiber optic cables. From medical diagnostics to high-tech manufacturing to the food industry, measuring polarization reveals critical data.
Scientists rely on polarimeters to make these measurements. While ubiquitous, many polarimeters currently in use are slow, bulky and expensive.
Now, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences and Innovation Center Iceland have built a polarimeter on a microchip, revolutionizing the design of this widely used scientific tool.
“We have taken an instrument that can reach the size of a lab bench and shrunk it down to the size of a chip,” said Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering, who led the research. “Having a microchip polarimeter will make polarization measurements available for the first time to a much broader range of applications, including in energy-efficient, portable devices.”
“Taking advantage of integrated circuit technology and nanophotonics, the new device promises high-performance polarization measurements at a fraction of the cost and size,” said J. P. Balthasar Mueller, a graduate student in the Capasso lab and first author of the paper.
The device is described in the journal Optica. Harvard’s Office of Technology Development has filed a patent application and is actively exploring commercial opportunities for the technology.