Researchers at the University at Buffalo are developing a technology of slowing and absorbing certain wavelengths of light offering new possibilities in solar power, thermal energy recycling and stealth technology more efficient photovoltaic cells and improved radar and stealth technology.
That’s a big bite, but also add a new way to recycle waste heat generated by machines into energy. All from a breakthrough in photonics research.
The image shows a “multilayered waveguide taper array.” The different wavelengths, or colors, are absorbed by the waveguide tapers (thimble-shaped structures) that together form an array.
The work was published March 28 in the journal Scientific Reports. The paper explores the use of a nanoscale microchip component called a “multilayered waveguide taper array” that improves the chip’s ability to trap and absorb light.
Unlike today’s flat chips, the waveguide tapers as seen the thimble-shaped structures pictured above, slows and ultimately absorbs each frequency of light at different places along the vertical wall to catch a full “rainbow” of wavelengths, or more complete broadband of light.
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Lead researcher Qiaoqiang Gan, PhD, UB assistant professor of electrical engineering said, “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.”
Each multilayered waveguide taper is made of ultrathin layers of metal, semiconductors and/or insulators. The tapers absorb light in metal dielectric layer pairs, the so-called 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.
Such a versatile structure could lead to advancements in a very wide array of fields.
For example, there is a relatively new field of advanced computing research called on-chip optical communication. In this field, there is a phenomenon known as crosstalk, in which an optical signal transmitted on one waveguide channel creates an undesired scattering or coupling effect on another waveguide channel. The multilayered waveguide taper structure array could potentially prevent this.
It could also improve thin-film photovoltaic cells, which are a promising because they are less expensive and more flexible than traditional solar cells. The drawback, however, is that they don’t absorb as much light as traditional cells. Because 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.
The multilayered waveguide taper array could help recycle waste heat generated by power plants and other industrial processes, as well as electronic devices such as televisions, smartphones and laptop computers.
Dengxin Ji, a PhD student in Gan’s lab and first author of the paper said, “It could be useful as an ultra compact thermal-absorption, collection and liberation device in the mid-infrared spectrum.”
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Haomin Song, another PhD student in Gan’s lab and the paper’s second author added that it could even be used as a stealth, or cloaking, material for airplanes, 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.”
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Additional authors of the paper include Haifeng Hu, Kai Liu, Xie Zeng and Nan Zhang, all PhD candidates in UB’s Department of Electrical Engineering.
While the research is just getting going in the lab the idea holds promise for impacting a broad range of energy technologies ranging from photovoltaics, to thin-film thermal absorbers/emitters, to optical-chemical energy harvesting. This is no small idea.
Its welcome work deserving congratulations.
By Brian Westenhaus
