Control of terahertz light by spin Proof of principle of new electromagnetic optical device

Rotation of terahertz light polarization and the change of terahertz light intensity when the terahertz light propagates through the magnet. © Noriaki Kida

Controlling the direction (polarization) and oscillation amplitude of light (electromagnetic waves) has enabled the creation of devices with a wide range of functions. The frequency of electromagnetic waves employed in such devices continues to increase, and it will not be long until 10¹¹ hertz wireless communication becomes possible. However, the difficulty of controlling the amplitude or polarization of terahertz (10¹²) electromagnetic waves, the frequencies to be employed in the next generation of RF communication devices, has been an obstacle to device development.

Professor Yoshinori Tokura (University of Tokyo’s Graduate School of Engineering and RIKEN Strongly Correlated Quantum Science Research Group Director), Associate Professor Noriaki Kida (Graduate School of Frontier Sciences), Project Researcher Sandor Bordacs (Graduate School of Engineering Quantum-Phase Electronics Center), and their colleagues have demonstrated the massive rotation of polarized light through 90 degrees for each millimeter it propagates through a Ba₂CoGe₂O₇ crystal, employing electron spin, the property that underlies magnetism. In addition, the team demonstrated that light intensity can be increased or decreased up to 100% by application of a magnetic field. This phenomenon is due to what is termed the magneto-chiral effect, and is completely unrelated to the conventional effect of magnetic fields on light. Both of these phenomena were observed in the terahertz range, this research provides a step toward the realization of technology for the control of polarization and amplitude of terahertz electromagnetic waves.

Department release/press release (Japanese)

Paper

S. Bordacs, I. Kezsmarki, D. Szaller, L. Demko, N. Kida, H. Murakawa, Y. Onose, R. Shimano, T. Room, U. Nagel, S. Miyahara, N. Furukawa, and Y. Tokura,
“Chirality of matter shows up via spin excitations,”
Nature Physics Online Edition: 2012/8/27 (Japan time), doi: 10.1038/NPHYS2387
Article link

Links

Graduate School of Engineering

Graduate School of Frontier Sciences

Department of Applied Physics

Quantum-Phase Electronics Center

Tokura Lab

RIKEN