Topic:
Left: Calculated first principles dielectric constant and refractive index of rhombohedral ferroelectric BiFeO3, showing the large differences between directions parallel and orthogonal to the ferroelectric polarization. Right: simplified potential device geometry, with dimensions in microns and the calculated device performance.
Ferroelectric BiFeO3 was found to have an exceptionally high infrared optical response to polarization rotation. Understanding the coupling between a material’s optical response and an applied external bias is a prerequisite to the development of new optical switches, sensors, and other photonic technologies. First principles calculations of optical properties combined with electro-magnetic modeling for a plasmonic device geometry now showed that this material provides much improved performance compared to current materials. In fact, the infrared refractive index along the polarization direction differs dramatically from that perpendicular to it due to the high ferroelectric polarization and the rotation of the FeO6 octahedra in the crystal structure. The coupling of polarization to electric field therefore implies a large tunability of the optical response using electric control. Modeling showed that this yields large performance increases in a plasmonic switch model. Plasmonic devices can be used for near field coupling of light to nanoscale devices. The finding of a high response ferroelectric thus opens new opportunities for optical communication technology and scientific experiments probing nanoscale phenomena with infrared light.
For more information contact David J. Singh, singhdj@ornl.gov.
S. H. Chu, D. J. Singh, J. Wang, E. P. Li, and K. P. Ong, “High optical performance and practicality of active plasmonic devices based on rhombohedral BiFeO3,” Laser Photonics Rev. 6, No. 5, 684–689 (2012) / DOI 10.1002/lpor.201280022.