Polarizers and waveplates are typical optics used to manipulate the state of light polarization while the opposite action (using polarized light to manipulate matter) seems elusive. This is largely because under the illumination of polarized light, matter experiences very weak preferential excitation or forces along the polarization which mostly results in no obvious effect unless some enhancing mechanism is applied, such as plasmonic or Mie resonances.
A group of researchers from Wuhan University has found a way to capture these polarizations by directly growing nanostructures along the polarization based on properly devised photochemistry. They found that it is possible to further engineer the polarization into more complex patterns so that the as-grown materials with the same complexity can be facilely generated, which opens a new paradigm of laser fabrication. Related works were recently published in Nature Communications and PNAS.
“Results never come easily, and this is fantastic!” said Tao, the corresponding author of the paper. “Now arbitrary nanopatterns are easy to get simply by engineering the light polarization, which is helpful in dispensing traditional labor-intensive and time-consuming top-down lithography to get complex nanostructures.” This is indeed possible as they can easily adjust the chiral patterns by continuously tweaking the spirality of the polarization with a vortex waveplate.
“Currently, we only find a few typical material systems that work with such polarization-directed growth,” said Xiaolin, the first author of the paper. “It requires proper growth kinetics of the nanoparticles under laser irradiation so that you won’t get a mess. Fortunately, we found that several precursors of Au, PtO, PdO and CdS worked well, representing different types of inorganic materials. However, more exploration is required to unlock other materials with interesting optic, electric or magnetic properties.”
Right now, the team is attempting to make the results more scalable and generally applicable on different substrates. Tunability of the chiral structure will also be an important aspect of their future efforts. With a patent on related technology, the team hopes to commercialize it for the fabrication of chiral metasurfaces in the near future.
