Oct 112017
 

via WT VOX

The theoretical discovery of transparent particles that break the previously accepted limit of visibility opens a new door in the search for perfect transparency

Transparent particles with extraordinarily high refractive indices can become almost invisible at wavelengths longer than the particle size, an A*STAR-led theoretical study has shown1. The discovery challenges the accepted wisdom around the limits of light scattering and visibility, and could lead to a new class of ‘invisible’ materials.

The scattering of sunlight from gas molecules in the atmosphere is what makes the sky look blue, allowing us to effectively see what would other be a transparent medium. This process, known as Rayleigh scattering, occurs when molecules or particles are smaller than the wavelength of light that hits them. It has long been accepted that all particles undergo Rayleigh scattering, and that the minimum amount of scattering occurs when the refractive index — a measure of the ‘slowness’ of light passing through a medium compared with a vacuum — is less than two. Water, air and glass all meet this condition, suggesting that the Rayleigh scattering that makes the sky blue is the least visible state physically achievable.

Boris Luk’yanchuk and colleagues from the A*STAR Data Storage Institute, in collaboration with researchers from the Australian National University, have now upset this status quo with the discovery that Rayleigh scattering can be suppressed in transparent particles at wavelengths longer than the particle scale if their refractive index is extraordinarily high.

“There have been many attempts to reduce scattering,” says Luk’yanchuk. “For example, suppression of the back reflection of radar signals has been widely studied as part of the development of stealth technology. Yet even very small transparent particles have some degree of scattering. We have been able to reveal a new phenomenon that could be used to design ultra-transparent optical materials.”

Rayleigh scattering occurs when light is absorbed by a molecule — producing a separation of positive and negative charges known as an electric dipole — and re-emitted by the dipole at the same energy. This can occur at all wavelengths, but is more efficient at short wavelengths, which is why the sky is more blue (short wavelength) than red (long wavelength).

“In our theoretical study we found that for very high refractive index materials, the contribution of the electric dipole becomes vanishingly small,” explains Luk’yanchuk. “Specifically, we found that the electric dipole mode in small particles of such materials is suppressed by the emergence of another dipole mode, resulting in ultra-weak scattering below the Rayleigh limit. The challenge now is to find or develop materials with a high enough refractive index at the wavelength of interest to suppress Rayleigh scattering.”

Learn more: Invisibility is within sight

 

The Latest on: Invisibility
  • The Best Quick-Fix Spot Treatments To Clear Up Pimples Fast — At Every Price Point
    on January 23, 2018 at 4:03 am

    Invisibility could save you a lot of embarrassment, the perfect escape tactic for those moments when the person who takes your ticket at the movie theater tells you to enjoy the film and you say, "You too!" But the most super of all possible superpowers ... […]

  • ‘Incredibles 2’ Voice Cast and Concept Art Reveal New Characters and Plot Details
    on January 22, 2018 at 6:58 pm

    Socially awkward, outspoken and sarcastic, Violet plays her teenager role to perfection—all while secretly mastering her superpowers of invisibility and creating force fields. A Super at heart, Violet can’t help her urge to fight crime alongside her ... […]

  • Are Cloaking Devices Coming? Metalens-Shaped Light May Lead The Way
    on January 22, 2018 at 1:01 pm

    For as long as human beings have been writing about fantasy, myth, and science fiction, the dream of invisibility has always been a top priority. While Star Trek brought the idea of a cloaking device into the popular consciousness, the closest we’ve come ... […]

  • ‘Incredibles 2’ Voice Cast and Characters Revealed in Clever New Images
    on January 22, 2018 at 12:47 pm

    Socially awkward, outspoken and sarcastic, Violet plays her teenager role to perfection—all while secretly mastering her superpowers of invisibility and creating force fields. A Super at heart, Violet can’t help her urge to fight crime alongside her ... […]

  • New Incredibles 2 Characters and Main Cast Revealed
    on January 22, 2018 at 10:29 am

    Socially awkward, outspoken and sarcastic, Violet plays her teenager role to perfection, all while secretly mastering her superpowers of invisibility and creating force fields. A Super at heart, Violet can't help her urge to fight crime alongside her family. […]

  • Silence is Violence
    on January 19, 2018 at 10:45 pm

    John Pavlovitz explains how the silent treatment adds worse insult than injury to a person. It adds invisibility. Over the last few months as I’ve talked with people reeling from the devastation of fractured relationships, those standing beneath the ... […]

  • Erasure: Blackness and the Fight Against Invisibility
    on January 19, 2018 at 11:10 am

    Oppression can take many shapes, from violence to enslavement to disenfranchisement, but one of the most pervasive and pernicious forms is "erasure," a process by which individuals or groups are made invisible. This semester, Bucknell's Griot Institute for ... […]

  • New Class of Light-Bending Material Spun With DNA and Gold Nanoparticles Can Achieve First Real-Life Invisibility Cloak
    on January 19, 2018 at 4:33 am

    In a huge achievement spanning both chemistry and physics, scientists have found a way to create entirely new classes of material that can bend oncoming light around them, making them appear invisible. No, that is not hyperbole, and yes, this is how the ... […]

  • The Invisibility of Being Old, Disabled or Both
    on January 13, 2018 at 6:45 pm

    When you’re an older person in a wheelchair or walking with a cane, people treat you differently. Sure, some might be quicker to open doors for you, but most of the behavioral reactions aren’t positive ones. The combination of being old and disabled ... […]

  • Invisibility Cloak Spinoff Marks Commercial Debut with Fractal Metamaterials
    on January 12, 2018 at 7:41 am

    BEDFORD, Mass.--(BUSINESS WIRE)--A spinoff of invisibility cloak technology has finally seen the lights and glitz of Las Vegas, as Fractal Antenna Systems, Inc. (FRACTAL) debuted its breakthrough fractal metamaterial technology (FM/R) at the CES. […]

via Google News and Bing News

Other Interesting Posts

Leave a Reply

%d bloggers like this: