Department News

BC Physicists Have Beamed Visible Light Through Nanocoax Cable

Physicists at Boston College have beamed visible light through a cable hundreds of times smaller than a human hair, an invention that may some day lead to novel applications in optical communications, computing and medicine.

The team consists of BC Physics Professors Kris Kempa, Zhifeng Ren, Andrzej Herczynski and Department Chairman Michael J. Naughton, Postdoctoral Fellow Dr. Jakub Rybczynski, former BC graduate students Dr. Yang Wang and Dr. Zhongping Huang (now at NanoLab Inc. in Newton, Mass.), Dr. Dong Cai of NanoLab (now at BC), and Dr. Michael Giersig of the Center for Advanced European Studies and Research in Bonn, Germany.

The results of their work appear in the Jan. 8 issue of Applied Physics Letters.

Schematic of a coaxial cable (a) and SEM image of a nanocoax (b)

Using an analogy with the conventional coaxial cable which carries the electromagnetic signals, BC physicists have designed a nanoscale coaxial cable. It can propagate light over distances of many wavelength through wires with coaxial electrode spacing much less than one wavelength. "Our coax works just like the one in your house, except now for visible light," says Jakub Rybczynski, lead author on the publication.

Their nanoscopic coaxial cable, which they have dubbed a “nanocoax”, contains an inner wire of carbon nanotube, the preparation of which has been pioneered by Prof. Ren.  This nanotube is surrounded by an insulating aluminium oxide layer and then an outer metallic layer, with the center wire sticking out at one end to serve as an antenna for receiving light. According to Prof. Kempa, this optical antenna allows for the guiding of light into the structure, even though, normally, light waves cannot penetrate structures smaller than their wavelength. In fact, the researchers have squeezed visible light having a wavelength of 380-750 nanometers through a light-transmitting coaxial cable which is only about 300 nanometers wide.

This invention can lead to many innovations in the manipulation of visible light on the nanoscale, such as light-based switching devices for optical computing and even high efficiency solar power. It may also find utility in the medical arena treating vision ailments.