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Stanford Scientists Trap and Redirect Light with Resonant Nanoantennas

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STANFORD, Calif., Sept. 1, 2020 — Researchers in the lab of professor Jennifer Dionne at Stanford University have structured ultrathin silicon chips into nanoscale bars to resonantly trap light, and then release or redirect it later. “We’re essentially trying to trap light in a tiny box that still allows the light to come and go from many different directions,” researcher Mark Lawrence said, of the method that slows and directs light particles at will.

A central component of these “high-quality-factor“ or “high-Q“ resonators is an extremely thin layer of silicon, which traps light efficiently and has low absorption in the near-infrared — the spectrum that the researchers are interested in controlling. The silicon rests on top of a wafer of transparent material (sapphire, in this case) into which the researchers direct an electron microscope pen to etch a nanoantenna pattern. The pattern must be drawn as smoothly as possible, as the antennas serve as the “walls” that hold in the light, and imperfections inhibit their light-trapping ability.

An artist rendering of a high-Q metasurface beam-splitter. These “high-quality-factor” or “high-Q” resonators could lead to new ways of manipulating and using light. Courtesy of Riley A. Suhar/Stanford University.
An artist rendering of a high-Q metasurface beamsplitter. These 'high-quality-factor' or 'high-Q' resonators could lead to new ways of manipulating and using light. Courtesy of Riley A. Suhar.

Pattern design plays a key role in creating the high-Q nanostructures. “High-Q resonances require the creation of extremely smooth sidewalls that don’t allow the light to leak out,” Dionne said. “That can be achieved fairly routinely with larger micron-scale structures, but is very challenging with nanostructures, which scatter light more.”

The researchers found a pattern design that performed well and could be created using existing fabrication methods. The optical transfer function, near-field intensity, and resonant line shape could all be rationally designed, providing a foundation for efficient, free-space-reconfigurable, and nonlinear nanophotonics.


While beam-steering light to selected directions, the nanostructures demonstrated quality factors of about 2500. This is two orders of magnitude higher than similar devices have achieved, the researchers said. Quality factors, or Q-factors, are a measure used to describe resonance behavior, which in this case is proportional to the lifetime of the light. “By achieving quality factors in the thousands, we're already in a nice sweet spot for some very exciting technological applications,” Dionne said.

The high-Q resonators could lead to new ways to manipulate and use light, including new applications for quantum computing, virtual and augmented reality, light-based WiFi, and even the detection of viruses like SARS-CoV-2. Currently, Dionne’s lab is working on applying its technique for slowing and steering light to detecting COVID-19 antigens and antibodies.

“Our technology would give an optical readout like the doctors and clinicians are used to seeing,” Dionne said. “But we have the opportunity to detect a single virus or very low concentrations of a multitude of antibodies owing to the strong light-molecule interactions.” The high-Q nanoresonators are designed to allow each antenna to operate independently to detect different types of antibodies simultaneously.

Dionne is also interested in using the device for lidar applications and in quantum science. “A few years ago I couldn’t have imagined the immense application spaces that this work would touch upon,” she said. “For me, this project has reinforced the importance of fundamental research. You can’t always predict where fundamental science is going to go or what it’s going to lead to, but it can provide critical solutions for future challenges.”

The research was published in Nature Nanotechnology (www.doi.org/10.1038/s41565-020-0754-x). 

Published: September 2020
Glossary
nano
An SI prefix meaning one billionth (10-9). Nano can also be used to indicate the study of atoms, molecules and other structures and particles on the nanometer scale. Nano-optics (also referred to as nanophotonics), for example, is the study of how light and light-matter interactions behave on the nanometer scale. See nanophotonics.
quantum
The term quantum refers to the fundamental unit or discrete amount of a physical quantity involved in interactions at the atomic and subatomic scales. It originates from quantum theory, a branch of physics that emerged in the early 20th century to explain phenomena observed on very small scales, where classical physics fails to provide accurate explanations. In the context of quantum theory, several key concepts are associated with the term quantum: Quantum mechanics: This is the branch of...
lidar
Lidar, short for light detection and ranging, is a remote sensing technology that uses laser light to measure distances and generate precise, three-dimensional information about the shape and characteristics of objects and surfaces. Lidar systems typically consist of a laser scanner, a GPS receiver, and an inertial measurement unit (IMU), all integrated into a single system. Here is how lidar works: Laser emission: A laser emits laser pulses, often in the form of rapid and repetitive laser...
nanophotonics
Nanophotonics is a branch of science and technology that explores the behavior of light on the nanometer scale, typically at dimensions smaller than the wavelength of light. It involves the study and manipulation of light using nanoscale structures and materials, often at dimensions comparable to or smaller than the wavelength of the light being manipulated. Aspects and applications of nanophotonics include: Nanoscale optical components: Nanophotonics involves the design and fabrication of...
Research & TechnologyAmericasStanford UniversityLight SourcesOpticshigh quality factor resonatorslight trappinglight scatteringnanonanoantennascoronavirusCOVID-19Jennifer Dionnequantumlidarmetamaterialsmicroresonatorssilicon photonicsnanophotonicslight-matter interaction

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