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.