Efficient optical coupling of single carbon nanotubes to photonic crystals - An important step towards nanoscale photonic devices -
A University of Tokyo research group led by Yuichiro Kato at the Graduate School of Engineering and Yasuhiko Arakawa at the Institute of Industrial Science succeeded in achieving high efficiency optical coupling of over 85% of individual carbon nanotube emitters to photonic crystal structures.
Single-walled carbon nanotubes are known to be bright emitters in the telecommunication wavelength that can be grown directly on silicon, making them attractive for applications in nanoscale photonic devices. In particular, air-suspended carbon nanotubes show excellent emission properties, but efficiency of their optical coupling to photonic structures has remained low.
The research group has drastically improved the coupling efficiency by utilizing a specially designed photonic crystal structure. In contrast to conventional structures which confine light within the silicon material, the new design allows light from carbon nanotubes to fill air holes, increasing the optical interaction with air-suspended carbon nanotubes and greatly increasing the propagation of light within the optical resonator. The results demonstrate advantages of such a design for atomic layer materials, and are an important step towards nanoscale photonic devices with new functionalities.