'Carpet cloaks', which have sprung from the researchers' efforts, are being described as the first technology to succeed in hiding objects by deflecting light across a range of wavelengths.
Even though the novel technology is not capable of hiding the entire body of a human being, the researchers say that it may enable spies to conceal microphones under the rug or the wallpaper.
Scientists attending the conference heard that both new carpet cloaks work in infrared light, which has a wavelength far shorter than microwaves, and, in principle, could hide objects in normal light.
Instead of deflecting light waves around an object, both set-ups involve hiding bumps on a thin layer of material.
Illuminating the bump from the side would normally cast a dark shadow. But with the cloaks, the light is reflected uniformly so that there is no shadow, and the cloaked surface appears flat.
At Berkeley, a research team led by Jensen Li made their invisibility cloak by drilling nano-scale holes into a micrometer-thick layer of silicon.
At Cornell, Lucas Gabrielli's team achieved a similar effect by embedding 50-nanometre silicon posts into silicon dioxide.
Currently, the carpet cloaks are capable of working on ly in two dimensions.
The researchers, however, insist that these cloaks are astonishing because they use well-known materials and production methods.
Georg von Freymann, of the Institute of Nanotechnology at the University of Karlsruhe in Germany, hailed the demonstrations as "very charming".
"It looks like real-world applications may come from this," New Scientist magazine quoted Freymann as saying.
The researchers are hopeful that with further advances, their cloaks would one day be able to hide objects on walls and floors or in satellite images.