Monday, January 01, 2007

From the Labs: Information Technology

Continued from page 1

By Kate Greene

Spinning Light
A system combining a magnetic material and a semiconductor could lead to spintronic devices that pack more data into beams of light

Source: "Reconstruction Control of Magnetic Properties during Epitaxial Growth of Ferromagnetic Mn_3-gGa on Wurtzite GaN(0001)"
Erdong Lu et al.
Physical Review Letters 97: 146101

Results: Arthur Smith, a professor of physics at Ohio University, and postdoc Erdong Lu have grown manganese gallium, a metal, on gallium nitride, a semiconductor commonly used to make blue lasers and light-emitting diodes. Smith and Lu believe that the new material could lead to room-­temperature lasers that exploit the spin of electrons (spintronics).

Why it matters: Lasers based on spintronics, rather than on conventional electronics, have the potential to increase bandwidth in optical networks. Currently, data is encoded as the frequency and phase characteristics of a beam of light. In a spintronic laser, however, electrons with a certain spin can create photons with a corresponding spin, resulting in polarized light. Using polarization to encode a light beam with data could increase the amount of information it can carry. But until now, researchers have lacked materials suitable for making spintronic lasers.

Methods: Using standard processes, Smith and Lu deposited a thin film of manganese gallium onto gallium nitride. Reflection high-energy electron diffraction revealed a smooth interface between the two materials--a necessity if electrons are to maintain their spin as they travel into the light-emitting semiconductor.

Next steps: Researchers must determine whether the spin characteristics of the electrons are indeed preserved. They must also test the material's light-­emitting properties to determine how well the spin of electrons translates into polarized light.