Tagged: Jennifer Dionne Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 2:42 pm on August 20, 2020 Permalink | Reply
    Tags: "Stanford scientists slow and steer light with resonant nanoantennas", , “High-Q” resonators, Biosensing, Jennifer Dionne, , , , ,   

    From Stanford University: Women in STEM-“Stanford scientists slow and steer light with resonant nanoantennas” Jennifer Dionne 

    Stanford University Name
    From Stanford University

    August 17, 2020
    Media Contact
    Ker Than
    Stanford News Service:
    (650) 723-9820
    kerthan@stanford.edu

    Written By Lara Streiff

    Researchers have fashioned ultrathin silicon nanoantennas that trap and redirect light, for applications in quantum computing, LIDAR and even the detection of viruses.

    1
    An artist rendering of a high-Q metasurface beamsplitter. These “high-quality-factor” or “high-Q” resonators could lead to novel ways of manipulating and using light. (Image credit: Riley A. Suhar)

    Light is notoriously fast. Its speed is crucial for rapid information exchange, but as light zips through materials, its chances of interacting and exciting atoms and molecules can become very small. If scientists can put the brakes on light particles, or photons, it would open the door to a host of new technology applications.

    Now, in a paper published on Aug. 17, in Nature Nanotechnology, Stanford scientists demonstrate a new approach to slow light significantly, much like an echo chamber holds onto sound, and to direct it at will. Researchers in the lab of Jennifer Dionne, associate professor of materials science and engineering at Stanford, structured ultrathin silicon chips into nanoscale bars to resonantly trap light and then release or redirect it later. These “high-quality-factor” or “high-Q” resonators could lead to novel ways of manipulating and using light, including new applications for quantum computing, virtual reality and augmented reality; light-based WiFi; and even the detection of viruses like SARS-CoV-2.

    “We’re essentially trying to trap light in a tiny box that still allows the light to come and go from many different directions,” said postdoctoral fellow Mark Lawrence, who is also lead author of the paper. “It’s easy to trap light in a box with many sides, but not so easy if the sides are transparent – as is the case with many Silicon-based applications.”

    Make and manufacture

    Before they can manipulate light, the resonators need to be fabricated, and that poses a number of challenges.

    A central component of the device is an extremely thin layer of silicon, which traps light very efficiently and has low absorption in the near-infrared, the spectrum of light the scientists want to control. The silicon rests atop a wafer of transparent material (sapphire, in this case) into which the researchers direct an electron microscope “pen” to etch their nanoantenna pattern. The pattern must be drawn as smoothly as possible, as these antennas serve as the walls in the echo-chamber analogy, and imperfections inhibit the light-trapping ability.

    “High-Q resonances require the creation of extremely smooth sidewalls that don’t allow the light to leak out,” said Dionne, who is also Senior Associate Vice Provost of Research Platforms/Shared Facilities. “That can be achieved fairly routinely with larger micron-scale structures, but is very challenging with nanostructures which scatter light more.”

    Pattern design plays a key role in creating the high-Q nanostructures. “On a computer, I can draw ultra-smooth lines and blocks of any given geometry, but the fabrication is limited,” said Lawrence. “Ultimately, we had to find a design that gave good-light trapping performance but was within the realm of existing fabrication methods.”

    High quality (factor) applications

    Tinkering with the design has resulted in what Dionne and Lawrence describe as an important platform technology with numerous practical applications.

    The devices demonstrated so-called quality factors up to 2,500, which is two orders of magnitude (or 100 times) higher than any similar devices have previously achieved. Quality factors are a measure describing 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 from some very exciting technological applications,” said Dionne.

    For example, biosensing. A single biomolecule is so small that it is essentially invisible. But passing light over a molecule hundreds or thousands of times can greatly increase the chance of creating a detectable scattering effect.

    Dionne’s lab is working on applying this technique to detecting COVID-19 antigens – molecules that trigger an immune response – and antibodies – proteins produced by the immune system in response. “Our technology would give an optical readout like the doctors and clinicians are used to seeing,” said Dionne. “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 design of the high-Q nanoresonators also allows each antenna to operate independently to detect different types of antibodies simultaneously.

    Though the pandemic spurred her interest in viral detection, Dionne is also excited about other applications, such as LIDAR – or Light Detection and Ranging, which is laser-based distance measuring technology often used in self-driving vehicles – that this new technology could contribute to. “A few years ago I couldn’t have imagined the immense application spaces that this work would touch upon,” said Dionne. “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.”

    This innovation could also be useful in quantum science. For example, splitting photons to create entangled photons that remain connected on a quantum level even when far apart would typically require large tabletop optical experiments with big expensive precisely polished crystals. “If we can do that, but use our nanostructures to control and shape that entangled light, maybe one day we will have an entanglement generator that you can hold in your hand,” Lawrence said. “With our results, we are excited to look at the new science that’s achievable now, but also trying to push the limits of what’s possible.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    Stanford University campus. No image credit

    Stanford University

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

    Stanford University Seal

     
  • richardmitnick 1:31 pm on October 5, 2017 Permalink | Reply
    Tags: An early interest in tricks of light led Dionne to begin wielding it as a tool during graduate school at Caltech and then her postdoc at UC Berkeley, , Jennifer Dionne, , ,   

    From ScienceNews: Women in STEM – “Jennifer Dionne harnesses light to illuminate nano landscapes” 

    ScienceNews bloc

    ScienceNews

    October 4, 2017
    Emily Conover

    Tiny particles could light the way to improved cancer tests or drugs with fewer side effects.

    1
    LEADING LIGHT Jennifer Dionne, 35 Materials scientist, Stanford University.
    Materials scientist Jennifer Dionne melds purpose and play in her work with matter and light. Timothy Archibald

    To choose her research goals, Jennifer Dionne envisions conversations with hypothetical grandchildren, 50 years down the line. What would she want to tell them she had accomplished? Then, to chart a path to that future, “I work backward to figure out what are the milestones en route,” she says.

    That long-term vision has led the 35-year-old materials scientist on a quest to wrangle light and convince it to do her bidding in interactions with nanoparticles and various materials. Already, Dionne has created new nanomaterials that steer light in ways that are impossible with natural substances. Her new projects could eventually lead to light-based technologies used to improve drugs or to create new tests to find cancerous cells. There are even applications for renewable energy, for example, designing materials that help solar cells absorb more light.

    But the route to a scientific vision may not always be clear, so Dionne makes time for diversions. “A lot of the really amazing discoveries that we enjoy today came from just playing in the lab,” she says. Dionne encourages her team to let creativity be a guide, melding a serious sense of purpose with play.

    “She’s a very curious person, so she’s always learning new things,” says Paul Alivisatos, the vice chancellor for research at the University of California, Berkeley, who mentored Dionne when she was a postdoc there. Plus, “she’s an extremely deep and rigorous thinker.”

    Dionne, now at Stanford University, studies nanophotonics, the way that light interacts with matter on very small scales. Her interest in light and materials began in childhood, she recalls, when she was fascinated by the blue morpho butterfly.

    The insect’s wings sport an azure hue that comes not from pigments, like most colors found in living things, but from tiny nanostructures on the wings’ surface (SN: 6/7/08, p. 26). When light reflects off the structures, blue wavelengths are amplified, while wavelengths corresponding to other colors are canceled out.

    That early interest in tricks of light led Dionne to begin wielding it as a tool during graduate school at Caltech and then her postdoc at UC Berkeley. Then and now, says Alivisatos, “she has consistently done very beautiful work.”

    At Caltech, Dionne and colleagues created a bizarre optical material in which light bends backward. As light passes from one material to another — say, from air to water — the rays are deflected due to a property called the index of refraction. (That’s why a straw in a drinking glass appears to be broken at the water’s surface.) In natural materials, light always bends in the same direction. But that rule gets flipped around in oddball nanomaterials with a negative index of refraction.

    2
    G. Dolling et al/Optics Express 2006
    Light rays bend as they pass from air into water, making a drinking straw look broken (illustrated in a computer-generated image, left). In materials with a negative index of refraction (right), light rays bend in the opposite direction they normally do, so that the straw appears flipped around.

    Dionne’s material, reported in Science in 2007, was the first that worked with visible light (SN: 3/24/07, p. 180). Because they can steer light around objects to hide the objects from view, such materials could be used to create rudimentary versions of invisibility cloaks — though so far all attempts are a far cry from Harry Potter’s version. Dionne is now working on a “squid skin” with an adjustable refractive index, which would mimic the shifting camouflage patterns of the stealthy cephalopod.

    Another focal point of Dionne’s research is harnessing light to separate mixtures of mirror-image molecules. Right- and left-handed versions of these molecules are perfect reflections of each other, like a person’s right and left hands. The two types are so similar that scientists struggle to separate them, which can cause problems for drugmakers. In drugs, these molecules can be two-faced; one might relieve pain, while the other causes unwanted side effects.

    To separate molecules and their mirror images, Dionne is developing techniques that use circularly polarized light, in which the light’s wiggling electromagnetic waves rotate over time. Such light can interact differently with right- and left-handed molecules, for example, breaking apart one version while leaving the other unscathed.

    Normally, the light’s effect is very weak. But in a theoretical study published in ACS Photonics last December, Dionne and colleagues showed that adding nanoparticles to the mix could enhance the process. These tiny particles behave like antennas that concentrate the light onto nearby molecules, helping break them apart. Dionne is now working to implement the technique.

    She and her colleagues have also created nanoparticles that, when illuminated with infrared light, emit visible light. The color of that light changes depending on how tightly the nanoparticle is squeezed, the team reported in Nano Letters in June. In keeping with her penchant for creative exploration in the lab, Dionne and colleagues fed these nanoparticles to roundworms, the nematode Caenorhabditis elegans, to study the forces exerted as a transparent worm squeezed a meal through its digestive tract.

    “You can see the nanoparticles change colors throughout,” Dionne says. She plans to use the technique to reveal more sinister squeezing. Cancer cells exert stronger mechanical forces on their environment than healthy cells, so such nanoparticles could one day be used to test for cancer, she says. Dionne is now cooking up other creative ways to use these nanoparticles. In collaboration with other researchers, she hopes to marshal her color-changing nanoparticles to understand how jellyfish move and how plants take a drink.

    Dionne’s work exploits light to reveal hidden forces — and as a force for good. “She’s done amazing work,” says materials scientist Prineha Narang of Harvard University. Narang was a graduate student at Caltech after Dionne left, and had heard chatter about Dionne before meeting her in person. “The legend of Jen Dionne was definitely all over,” Narang says. So Dionne has made a start at establishing her scientific legacy — even before that chat with her future grandchildren.

    At the full article many citations with links.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: