In breakthrough photonics research from University at Buffalo, a nanoscale microchip component called a “multilayered waveguide taper array” has been demonstrated that absorbs each frequency of light at different places vertically to catch a “rainbow” of wavelengths, or broadband light.
Unlike current chips, the waveguide contains specialized tapers, the thimble-shaped structures pictured here.
The work opens up new possibilities for more efficient photovoltaic cells, improved radar and stealth technology and new ways to recycle waste heat generated by machines into energy.
“We previously predicted the multilayered waveguide tapers would more efficiently absorb light, and now we’ve proved it with these experiments. This advancement could prove invaluable for thin-film solar technology, as well as recycling waste thermal energy that is a byproduct of industry and everyday electronic devices such as smartphones and laptops,”
lead researcher Qiaoqiang Gan said.
Each multilayered waveguide taper is comprised of ultrathin layers of metal, semiconductors and/or insulators. The tapers absorb light in metal dielectric layer pairs, dubbed hyperbolic metamaterial.
By adjusting the thickness of the layers and other geometric parameters, the tapers can be tuned to different frequencies including visible, near-infrared, mid-infrared, terahertz and microwaves.
On-chip Optical Communication
One relatively new field of sophisticated computing research called on-chip optical communication may benefit from this breakthrough.
In this field, there exists an occurrence called crosstalk. Crosstalk is when an optical signal transmitted on one waveguide channel creates an unwanted scattering or coupling effect on another waveguide channel. The multilayered waveguide taper structure array potentially could prevent this.
It may also advance the state of the art in thin-film photovoltaic cells, promising because less expensive and more flexible than traditional solar cells. Their drawback is that they don’t absorb as much light as traditional cells.
Since the multilayered waveguide taper structure array can efficiently absorb the visible spectrum, as well as the infrared spectrum, it could potentially boost the amount of energy that thin-film solar cells generate.
Industrial and Consumer Applications
The multilayered waveguide taper array might also help recycle waste heat generated by power plants and other industrial processes, in addition to electronic devices such as smartphones, televisions, and laptop computers.
“It could be useful as an ultra compact thermal-absorption, collection and liberation device in the mid-infrared spectrum,”
says first author Dengxin Ji.
It could potentially even be used as a stealth cloaking material for aircraft, marine ships and other vehicles to avoid radar, sonar, infrared and other forms of detection.
“The multilayered waveguide tapers can be scaled up to tune the absorption band to a lower frequency domain and absorb microwaves efficiently,”
says Haomin Song, the paper’s second author.
Dengxin Ji, Haomin Song, Xie Zeng, Haifeng Hu, Kai Liu, Nan Zhang & Qiaoqiang Gan. Broadband absorption engineering of hyperbolic metafilm patterns. Scientific Reports 4, Article number:4498 doi:10.1038/srep04498
Linic, S., Christopher, P. & Ingram, D. B. Plasmonic-metal nanostructures for efficient conversion of solar to chemical energy. Nature Mater. 10, 911–921 (2011)