A new, flat lens
with the ability to focus light with a higher efficiency within the visible
spectrum was reported by a team of researchers from the Harvard
John A. Paulson School of Engineering and Applied Sciences (SEAS) last
summer. In order to bend and focus light as it passed, an ultrathin array of
nanopillars was used in the lens.
The report was acknowledged
as a major advancement in the field of optics and was mentioned as one of the
Science Magazine’s top discoveries in the year 2016.However, one drawback in
the lens was that it could focus only one color at a time.At present, the same
team has produced the first flat lens with the ability to function within a
continual bandwidth of colors, i.e. from blue to green. While being close to
the bandwidth of an LED, this bandwidth opens the door for new applications in
spectroscopy, imaging, and sensing.The study has been published in Nano
Letters.One main problem faced by researchers developing a flat, broadband lens
is correcting for chromatic dispersion, or the phenomenon in which different
wavelengths of light get focused at different distances from the lens.
Therefore, in optics, it is highly
significant to correct for chromatic dispersion, i.e. performing dispersion
engineering, which is an important design requisite in any optical system
dealing with light of different colors. The capacity of controlling the
chromatic dispersion in flat lenses expands their implementation and makes way
for new applications that are not practicable till date.In an attempt to initiate the
commercialization of this technology by setting up a startup company, Harvard’s
Office of Technology Development has filed patent applications on a portfolio
of flat lens technologies and is working in collaboration with Capasso as well
as researchers in his team.Alexander Zhu, Wei Ting Chen, Vyshakh Sanjeev, and
Aun Zaidi coauthored the published study. The research was partially supported
by the Air Force Office of Scientific Research. This research was carried out
in part at Harvard University’s Center for Nanoscale Systems (CNS)—a member of
the National Nanotechnology Coordinated Infrastructure (NNCI), in turn
supported by the National Science Foundation.
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