IRG-III Highlight
One-way photonic behavior
Figure: Microwave waveguide supporting CESs. |
What:
Research funded in part by the MIT MRSEC has led to a discovery of one-way photonic behavior. A team made up of MIT physicists Zheng Wang, research scientist in MIT's Research Laboratory of Electronics; recent MIT PhD recipient Yidong Chong; Professor John Joannopoulos; and Professor Marin Soljacic have developed and experimentally tested photonic crystals that restrict light to travel in only one direction without back-scattering, even in the presence of large disorders. In experiments, a microwave light beam is sent through the edge (a waveguide) of an array of small ceramic rods placed under an external magnetic field. Rather than bounce back or reflect, the light is able to move around obstacles and defects in its path without scattering.
So What:
This concept could be used to create one-way conduits in lightwave circuits, increasing their capacity and efficiency. Potential practical applications include optical information storage. This research also opens up a wide range of possibilities of using photonic structures to study topological orders that was so far only observed in electronic systems. This work was funded by the Army Research Office (Institute for Soldier Nanotechnologies), and the National Science Foundation (MRSEC program).
Paper:
Observation of unidirectional backscattering-immune topological electromagnetic states. Zheng Wang, Yidong Chong, J. D. Joannopoulos & Marin Soljacic. Nature, Vol 461, October 8, 2009.
Figure explanation:
(a) Schematic of the waveguide composed of an interface between a gyromagnetic photoniccrystal slab (blue rods) and a metal wall (yellow). The structure is sandwiched between two parallel copper plates (yellow) for confinement in the z direction and surrounded with microwave-absorbing foams (grey regions). Two dipole antennas, A and B, serve as feeds and/or probes. A variable-length (l) metal obstacle (orange) with a height equal to that of the waveguide (7.0mm) is inserted between the antennas to study scattering. A 0.20-T d.c. magnetic field is applied along the z direction using an electromagnet (not shown). (b) Top view (photograph) of the actual waveguide with the top plate removed.
