Published in Nature Nanotechnology, the team's research is also featured in the Stanford News. By structuring nanowires in a way that mimics geckos' ears, this team has found a way to record the incoming angle of light. This technology could have applications in robotic vision, photography and augmented reality.
"The typical way to determine the direction of light is by using a lens. But those are big and there's no comparable mechanisms when you shrink a device so it's smaller than most bacteria," states co-author and EE professor Shanhui Fan.
More detailed light detection could support advances in lens-less cameras, augmented reality and robotic vision, which is important for autonomous cars.
A long-term commitment This project began when co-author Dr. Zongfu Yu (EE postdoc & research associate '09-'13), was a student in Shanhui Fan's lab and took the initiative to combine his work there with research by Mark Brongersma and his lab. They made progress but had to put the work on hold while Yu applied for faculty positions and, subsequently, established his lab at the University of Wisconsin-Madison, where he is now an assistant professor of electrical and computer engineering and in whose lab Soongyu Yi works.
Many years later, and after publishing the current proof-of-concept, the researchers said they look forward to building on their results. Next steps include deciding what else they might want to measure from light and putting several nanowires side-by-side to see if they can build an entire imaging system that records all the details they're interested in at once.
"We've worked on this for a long time – Zongfu has had a whole life story between the start and end of this project! It shows that we haven't compromised on quality," Professor Brongersma said. "And it's fun to think that we might be here for another 20 years figuring out all the potential of this system."
Congratulations to all the authors!
Authors include: Soongyu Yi; Ming Zhou; Zongfu Yu; Pengyu Fan; Nader Behdad; Dianmin Lin (PhD, '16); Ken Xingze Wang; Shanhui Fan; Mark Brongersma. Abstract: Sensing the direction of sounds gives animals clear evolutionary advantage. For large animals, with an ear-to-ear spacing that exceeds audible sound wavelengths, directional sensing is simply accomplished by recognizing the intensity and time differences of a wave impinging on its two ears. Recent research suggests that in smaller, subwavelength animals, angle sensing can instead rely on a coherent coupling of soundwaves between the two ears. Inspired by this natural design, here we show a subwavelength photodetection pixel that can measure both the intensity and incident angle of light. It relies on an electrical isolation and optical coupling of two closely spaced Si nanowires that support optical Mie resonances. When these resonators scatter light into the same free-space optical modes, a non-Hermitian coupling results that affords highly sensitive angle determination. By straightforward photocurrent measurements, we can independently quantify the stored optical energy in each nanowire and relate the difference in the stored energy between the wires to the incident angle of a light wave. We exploit this effect to fabricate a subwavelength angle-sensitive pixel with angular sensitivity, δθ = 0.32°. Source, Nature Nanotechnology.
Paper link www.nature.com/articles/s41565-018-0278-9
- Stanford News, "Stanford engineers develop tiny light detectors that work like gecko ears", October 29, 2018.
- "Dianmin Lin (PhD '16) awarded the 2017 QEP Doctoral Research Prize", June 2017.