First-ever demo of a 3-D invisibility cloak for visible light

Joachim Fischer of the Karlsruhe Institute of Technology in Germany will present the first-ever demonstration of a three-dimensional invisibility cloak that works for visible light at at 10:15 a.m. Monday, May 2 at the Conference on Lasers and Electro-Optics (CLEO: 2011), which runs May 1–6 at the Baltimore Convention Center.

Wow … Harry Potter reality here I come … this sounds amazing. So here are some details.

The cloak works for red light at a wavelength of 700 nm—independent of its polarization (orientation). Previous cloaks required longer wavelength light, such as microwaves or infrared, or required the light to have a single, specific polarization.

Fischer makes the tiny cloak — less than half the cross-section of a human-hair — by direct laser writing (lithography) into a polymer material to create an intricate structure resembling a pile of logs. The precisely varying thickness of the “logs”enables the cloak to bend light in new ways.

Wait … how big!! …

The key to this achievement was incorporating several aspects of a diffraction-unlimited microscopy technique into the team’s 3-D direct writing process for building the cloak. The dramatically increased resolution of the improved process enabled the team to create spacings narrow enough to work in red light.

“If, in the future, we can halve again the log spacing of this red cloak, we could make one that would cover the entire visible spectrum,” Fischer added.

Practical applications of combining transformation optics with advanced 3-D lithography (a customized version of the fabrication steps used to make microcircuits) include flat, aberration-free lenses that can be easily miniaturized for use in integrated optical chips, and optical “black holes” for concentrating and absorbing light. If the latter can also be made to work for visible light, they will be useful in solar cells, since 90 percent of the Sun’s energy reaches Earth as visible and near-infrared light.

Presentation QTuG5 “Three-dimensional invisibility carpet cloak at 700 nm wavelength,” by Joachim Fischer et al. is at 11 a.m. Tuesday, May 3. Fischer et al. will also present CML1, “Three-Dimensional Laser Lithography with Conceptually Diffraction-Unlimited Lateral and Axial Resolution,” at 10:15 a.m. Monday, May 2.


Darn … OK, so I’d better put my Harry Potter costume back in the wardrobe … but what is this actually all about, its cannot be just a Harry Potter inspired bit of tech? … Nope, quite right, they actually have a far more practical use in mind.

Despite its Harry Potter-like allure, concealing tiny objects from view is not the team’s ultimate goal, Sun said. Rather, this latest demonstration shows that the new “transformation optics” principles and 3-D lithography techniques they used to make the cloak can also enable optical components for guiding, collimating, and focusing terahertz light in a variety of ways—in new medical and scientific diagnostic tools, airport security scanners, and data communication devices.

You can read a full press-release here.

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