Graphene can polarize light

Graphene, an ultra-flat monolayer of carbon atoms in a hexagonal crystal lattice, has attracted a strong wave of research interest due to its unique electrical and photonic properties.

As the first two dimensional material in the world, two UK Scientists were awarded the 2010 Nobel Prize in physics since it completely changes how we look at things. Now, Dr. Han Zhang at the Service OPERA-photonique – Applied Science Faculty, ULB – in collaboration with Prof. Loh at the National University of Singapore demonstrates the world's thinnest polarizer, which relies on the coupling, guiding and polarizing of electromagnetic waves by graphene.

They claim that this breakthrough will someday allow the integration on all-photonic circuits for high-speed optical communications.

Optical polarizers are elementary components of coherent and quantum optical communications by splitting the polarization state of an optical signal. Nowadays, there are rising demands for high-speed optical communications based on mobiles, calling for the miniaturization of optoelectronic devices. However, conventional optical polarizers (sheet, prism and Brewster-angle polarizer) are expensive, bulky, and discrete and may require additional alignment.

Thanks to graphene’s ultra-broadband optical property induced by its exceptional energy band structure, as-demonstrated graphene polarizer shows very broad operation bandwidth, at least from visible to mid-infrared. By fabricating graphene polarizer, with combined advantages of low cost (down to several euros), compact footprint, ultra-fast relaxation time and broad operation range, they anticipate that this device will enable new architectures for on-chip high-speed optical communications.

In addition to the industrial potentials, this research published in Nature Photonic, on May 30th is of fundamental importance.

It tackles how light propagates along an ultra-thin two dimensional surface. By the virtue of fiber based optical channel, now we can readily uncover how graphene guides and interacts with electromagnetic waves, with polarizing effect attributed to the differential attenuation of two polarization modes. This new conceptual finding will definitely lead to new physics, for example, localized waves or surface plasmon in graphene lattice. In the following years, researchers from the photonics, plasmonics and nano-science research communities may find in this graphene polarizer structure as a new testing ground for the ideas and methods they have been researching on their own fields, paving the way for all-carbon photonic-plasmonics devices.

Full bibliographic information
Qiaoliang Bao, Han Zhang, Bing Wang, Zhenhua Ni, Candy Haley Yi Xuan Lim, Yu Wang, Ding Yuan Tang, Kian Ping Loh. Broadband graphene polarizer. Nature Photonics, 2011; DOI: 10.1038/nphoton.2011.102
Contact :
Han Zhang, Service OPERA-Photonique, ULB
hzhang@ulb.ac.be, +32 (0)2 650 44 96