Using the evanescent field from a narrow strip waveguide, carbon nanotube photoluminescence is coupled with a microring resonator. The resonance of a microring can be easily tuned by adjusting the ring diameter, making it easy to match the emission wavelength of the carbon nanotubes. In a typical experiment, microrings have a diameter of 5 or 10 µm, and the carbon nanotubes will emit light around 1300 nm.

Highest quality yet

By depositing a thin layer of around 5 nm thick of PFO-extracted SWNTs on top of these microrings, and using a microphotoluminescence set-up, researchers from the Université Paris-Sud find that very sharp emission peaks are superimposed to the nanotube broad emission peaks. The quality factor (Q) of these emission peaks range from 3000 to 4000, which is the highest values reported so far for integrated silicon cavities coupled to carbon nanotubes.

Photoluminescence excitation spectroscopy is used to further investigate the origins of these peaks. Researchers show that these peaks disappear when the carbon nanotube emission intensity drops, demonstrating the coupling of nanotube light with silicon microrings.

Next steps

A range of possibilities for future photonic circuits is open, such as electrically driven carbon nanotube networks to produce light in the telecom wavelength range. The next step towards integration of carbon nanotubes into more complex photonic devices will be to investigate the electroluminescent properties of carbon nanotubes integrated into such devices.

More information about the research can be found in the journal Nanotechnology 25 215201.

Further reading

Nanotubes beam out bright light (Nov 2005)
Shedding more light on CNTs (Feb 2013)
Carbon nanotubes come under a polarized microscope (Nov 2013)