Black holes represent one of the most mysterious phenomena in the universe. Not only because we cannot observe them directly, but also because the incompatible concepts of general relativity and quantum mechanics are inescapably brought together by these objects.
While man-made black holes have featured in the press extensively over the last few years, thanks to the start of operations at the LHC, a collaboration of Chinese researchers have proposed a small-scale alternative [Lu et al., (2010) J Appl Phys, 108, 064517]. The researchers propose an artificial black hole made from metamaterials that is able to absorb and trap microwave radiation. Dr. Chen, co-author of the paper, explains “An artificial black hole is composed of two parts. The first part is graded refractive index medium that guides light into the second part (a perfect absorber)”. Although the system is far from representative of an actual black hole, such a system would allow researchers to study how electromagnetic radiation acts on passing by a black hole in the lab.
Metamaterials are composite materials which take on unusual properties due to their structures. While the individual components are typically rather ordinary, when combined incident electromagnetic radiation may exhibit exotic behavior. Recently metamaterials have come to prominence due to their potential use as superlenses, invisibility cloaks and superior antennas.
The idea of building an electromagnetic black hole is not new, but previous proposals have involved complicated structures. This new concept uses just five kinds of real material: air, aluminum metal, polyethylene, polymethyl methacrylate plexiglass and polyvinylidene fluoride. The materials are arranged as a series of layers, embedded with rods of aluminum and air. This proposed design consists of just twelve layers (additional layers provide a negligible increase) and although not a perfect absorber, calculations indicate that the simplified design is almost as effective as the more complicated structures. Chen is very confident that due to the straightforward design and availability of the materials, “there is no obstacle in building such a structure in the coming future”.
Thanks to the simplicity of the design the researchers are confident that the concept could be expanded to operate at higher frequencies. According to Chen, the next step of the project will be to “design an on-chip structure that can work for optical frequencies”.

Stewart Bland